Lister Engine Forum
How to / DIY => Everything else => Topic started by: BruceM on July 15, 2021, 08:34:35 PM
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This year's fires and record heat have forced my to re-consider adding a water chiller to my in floor heat system for some modest cooling. Since the house is only 1100SF and superinsulated, and based on tests with my neighbor's home using well water, about 12,000 BTU would just do it, and that's within my daytime PV/inverter power of 1500W at 230VAC. I only need to pull out about 4 degrees per day, my hot day heat gain which I normally can overcome with just opening windows at night. But not when smoky or clouds hold in the heat at night.
I've read all about refrigeration systems and understand the principles, but lack hands on experience.
Water chillers are grossly overpriced for their BTUs, using titanium clad heat exchanger assuming corrosive, oxygenated water. My heating system is closed loop, so that's a non-issue and so I'd like to use a tube in a tube or stainless plate type exchanger between refrigerant and the in-floor, recirculated water. This will require new tubing on the low pressure side.
I'd love to find a book or other resource so I can learn how to estimate the amount of refrigerant required after evacuating the assembled system. I would prefer to use a non-inverter mini split outside unit, or modified evaporator window AC unit with 3/8 pipe run of about 6 feet to the plate heat exhanger. Issues I need to learn include when to purge after brazing, how to calculate refrigerant charge and lubricant, how to adjust the evaporator valve for optimal efficiency.
Any suggestions for good texts or websites?
BruceM
I'm looking for the practical experimenter's guide to homebrew refrigeration, I suppose.
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way over my head.
But chilling the floor, will the coolness travel up into the house ?
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The notion that heat only rises is erroneous. Hold a hot pan just above your hand and feel the heat radiating downward . Transfer is better with lots of convective air flow, but using the floor provides so much area that it's not a problem; there is adequate room air movement to transfer heat from the room air, walls and ceiling to the cooled floor surface.
The use of in floor heat systems for cooling has been well proven. My house is superinsulated and the house temperature is within a few degrees of the tiled, insulated slab floor. In heating season, the floor is never actually warm except near the manifolds. For cooling, you must use water above the dew point, and it will not dehumidify so is appropriate for my high desert climate but not for others. New Mexico state paid for most the early research; they used unglazed night sky cooling panels to help pull heat out of commercial buildings at night. I did experiments with night sky and evaporative cooling a few years ago. I could never quite get water temperatures to the high 50F's, always mid 60's. You need water temperature a bit over near 15F cooler than the desired slab temp to get good transfer.
I'm having trouble finding a 12000-15000 BTU condenser unit drawing under 1500 watts continuous without variable speed inverter drive.
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Bruce,
I am a Refrigeration/HVAC tech. The trade and technologies within have changed a lot in the last decade. The only book I can recommend is "Modern Refrigeration and Air Conditioning". I am not sure when it was last updated so may be a little thin on some of the inverter technologies but is very good for basic principles. I will say that most Mini Split units will have a proprietary communication protocol between the indoor and outdoor units. They usually require at least a signal from a hall effect sensor on the indoor blower motor to run and will need temp sensor data from the indoor coil as well. You may be able to figure it out having an electronics background but you will need to replicate that signal to get the unit to run. I have had a similar system planned for years but instead of cooling a slab, building an ice bank. I have most of the pieces and parts salvaged from jobs over the years.
I haven't seen a non-inverter mini split in at least 15 years and don't believe they are available unless used so you may have to use a window banger instead. As far as purging practices the best practice is to always be purging especially with the modern refrigerants and oils, they don't like ANY moisture. I use a 2 stage regulator with 2 different low pressure settings to help prevent burning through so much nitrogen. The first is a purge setting which moves a fair amount of nitrogen through the system to displace the air and then switch to a braze setting which flows just enough nitrogen to keep the air out of the system. You want to be bleeding nitrogen the whole time you are brazing and you never want to leave the system open. Always seal it up and add some nitrogen to keep it dry. As far as estimating refrigerant charge that is going to be a big task as there are a lot of variables. The simplest thing to do is install a refrigerant sight glass in the liquid line and charge to a full sight glass with a target of at least a few degrees of sub cooling of the liquid. This is all dependent on the refrigerant you use and operating conditions. The charge is calculable using pipe volumes and density data for the specific refrigerant but in the end you will end up adjusting the charge for proper operation. I would be surprised if the system you are planning is more than 1-2 lbs of refrigerant.
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Thanks for the very helpful post, Bronco. I've got "Modern Refrigeration and Air Conditioning", but the 18th edition published in 2004. It is a good one. I'll check for a newer one. Storing surplus summer PV power in an ice bank is a great project that I'd love to read about.
You hit the nail on the head with the inverter type issue for my application. The reverse engineering required is something that I'd rather not do, and the EMI generated by such systems is something I'd like to avoid, despite the lovely soft starting they employ. So it looks like I'm stuck with a window unit.
Does the method of observing the dryer window for refrigerant charge assessment work for R410a? I think most new window AC units are now R410a...but I'm nof sure. If it would work, I'd put in a dryer w/ observation window to make charging easier. I have to research sub cooling and measurement as charge assessment. I recall the term but not how it's done and how to interpret it.
I do remember the important use of nitrogen to avoid oxidization on the tubing interior during brazing/silver soldering. I'll see if I can rent that from my gas/welding supplier.
I also want to thank 32coupe for his PM and speaking with me on the phone about my project. I sure appreciate the technical support!
Bruce
PS- here's an article on in-floor cooling for Mike. https://www.arcticheatpumps.com/radiant-floor-cooling.html
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Sight glass works on most stuff. But everything.
Dometic freezer units have a sight glass installed from the factory but they tell you
not to charge by filling the glass.
When they are correctly charged liquid will "trickle" through the glass.
That's 134a running an expansion valve to a plate or coil at low temps.
May not be applicable to your application but good brain exercise.
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Thanks for the very helpful post, Bronco. I've got "Modern Refrigeration and Air Conditioning", but the 18th edition published in 2004. It is a good one. I'll check for a newer one. Storing surplus summer PV power in an ice bank is a great project that I'd love to read about.
You are quite welcome. Hopefully one of these days I will have time to put it all together.
You hit the nail on the head with the inverter type issue for my application. The reverse engineering required is something that I'd rather not do, and the EMI generated by such systems is something I'd like to avoid, despite the lovely soft starting they employ. So it looks like I'm stuck with a window unit.
The EER of window units has come a long way in the last couple of years so it may not be as much of a sacrifice as you think. I think the simplicity would outweigh the gains had by an inverter, especially on a one off unit.
Does the method of observing the dryer window for refrigerant charge assessment work for R410a? I think most new window AC units are now R410a...but I'm nof sure. If it would work, I'd put in a dryer w/ observation window to make charging easier. I have to research sub cooling and measurement as charge assessment. I recall the term but not how it's done and how to interpret it.
Yes, in most cases. R-410A is a Zeotropic blend but it's properties are near Azeotropic meaning it acts nearly like a single component refrigerant with almost no glide. It really depends on your metering device. If you use a TXV setup then yes, you will likely always have a full sight glass when the system is running and stabilized. If you use a capillary tube or piston device you may have flash gas sometimes depending on the operating conditions. Capillary tubes and pistons are generally a compromise of best overall performance in a range of operating conditions for the sake of ease and cost of manufacture, where a TXV will always try to adjust to the most efficient operation but is a more expensive device.
Subcooling is the difference between your calculated condensing temperature(derived from A PT chart) and the measured liquid temperature. If your condensing temperature is 100 degrees and your measured liquid temperature is 85 degrees that is 15 degrees of subcooling. Most systems shoot for 10-15 degrees of subcooling. TXVs really prefer subcooled liquid as it guarantees no flash gas which can make them hunt and get stuck in a cycle of over and under correction. A capillary or piston system is usually charged using superheat at the compressor as well as pressures and amp draw to dial in the charge. Ultimately unless you are chasing the absolutely most efficient system possible either type system will work as refrigeration will work in a very broad range of conditions and accomplish what you are looking to do. If you go the window unit route a good starting point for charge would be to calculate the refrigerant volumes for whatever tubing lengths you add to the system and then add that to the factory charge stated on the data tag and that should get you to within a couple of ounces of the proper charge.
I do remember the important use of nitrogen to avoid oxidization on the tubing interior during brazing/silver soldering. I'll see if I can rent that from my gas/welding supplier.
I also want to thank 32coupe for his PM and speaking with me on the phone about my project. I sure appreciate the technical support!
Bruce
PS- here's an article on in-floor cooling for Mike. https://www.arcticheatpumps.com/radiant-floor-cooling.html
Responses in Red
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Thank you, Bronco, for the clear and detailed answers. You'd make an excellent instructor. It's a huge help.
Thanks again to 32Coupe, also.
I'll report back as I get further along.
Bruce
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Check out www.seafrost.com
Scan down the page to the spec charts.
Look at running amps, locked rotor and btu output. The numbers are interesting.
They obviously are not "the answer" but gives you an idea in that area.
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Hi Gary, I downloaded the manual and the charging section is quite helpful. Thanks!
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..... PS- here's an article on in-floor cooling for Mike. https://www.arcticheatpumps.com/radiant-floor-cooling.html
thanks !
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I ordered a refurbished 230V wall unit, 12000 BTU by LG to use as my compressor/condenser unit. It's R-410A as are almost all new units. I hope to use the dryer and evaporator capillary tube/piston valve and remove the evaporator and interior fan, replacing them with a brazed flat plate heat exchanger about 5 feet from the unit. I'm assuming I should move the capillary tube or piston valve to close to the new evaporator location, about 5-6 feet from the new condenser unit. I'll learn more after I take the LG unit apart.
Advice wanted:
1. For home use, is a dual stage vacuum pump worth it? Dual stage is nearly double the price, though still doable.
2. What about the acrylic HVAC rated glues for copper/brass as listed below? They eliminate the need for nitrogen/brazing, which saves me quite a bit of $ but makes me a bit concerned about reliability. I do have oxyacetylene for brazing. Many HVAC techs seem to skip nitrogen purge and fill for brazing but with the newer POE oils that seems hazardous in a small system like a modded 1 ton wall AC unit modded to be just a condenser unit. I have no practical experience here, only book learning.
https://www.amazon.com/ComStar-Copper-Solder-Plastic-Container/dp/B004Y753FM/ref=sr_1_1?dchild=1&keywords=comstar+copper+lock&qid=1628299152&sr=8-1
I've used this successfully on lower pressure copper without a problem, where a torch was not practical.
I'm skeptical about HVAC use because of pressure and vibration. When I move the evaporator valve/capillary tube to near the plate exchanger/evaporator that joint will see R-410A high pressure.
Because the LG 12000 btu wall unit is R-410a, I'm looking at higher pressure rated brazed heat exchangers. I found a chart for one vendor that gives me a range of acceptable sizes specifically for R410 evaporator use. A 30 plate Vevor 12x5 unit should not affect my low pressure/head circ pump much, and would handle almost triple the BTUs. Overkill but a bargain.
https://www.vevor.com/products/5x12-brazed-30-plate-heat-exchanger-1fnpt-316l-stainless-steel-w-bracket?_pos=13&_sid=477567439&_ss=r
I'll have to bush down the 1 inch F-NPT fittings but for the price, it's worth the hassle. If the flow restriction is low enough, I can simplify the plumbing and avoid bypass valves for winter operation. I'm adding a digital flow meter to my in floor system flow rate so I'll be able to see the impact is.
I've got a reclamation tank on order and plan to use the operating compressor for high side reclamation to an evacuated tank in ice water. This avoids the reclamation pump expense.
Thanks in advance!
Bruce M
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A dual stage vacuum pump is definitely prefered but not completely necessary. Dual stage pumps will ultimately pull a deeper vacuum and are faster. Find the ratings for the pump you are looking at and make sure it will pull down to at least 100 microns. Is there a harbor freight out your way? I broke a vacuum pump on a job a few years ago and needed one quick, grabbed a small cheap one from harbor freight and figured I would just toss it if it crapped out or have it as a backup but it has held up surprisingly well. It is definitely not near as fast as my larger and more expensive pumps but will get the job done. Should work fine on a small system like what you are working on.
I would not trust those glues at all. There is no information on chemical interaction with the refrigerant or refrigerant oil nor the pressures and temperature cycling it will experience in your water chiller system. If you want to avoid brazing you can always go the flare joint route. Just make sure you get flare nuts and fittings rated for refrigeration as they are forged and rated for higher pressure. They also eliminate the need to purge as you wouldn't be doing any brazing. You would still need some nitrogen to pressure test and for keeping the system dry until you are ready to evacuate and charge with refrigerant.
As far as techs skipping a nitrogen purge for brazing, that is just poor practice and asking for trouble in modern systems, especially a cap tube system. It is something that is in every piece of literature and recommendation associated with servicing equipment with modern refrigerants and oils. It ultimately comes down to experience with when and where a purge may not be necessary but it is best to just purge anytime one has to braze.
I would make sure that heat exchanger is rated for refrigerant. It looks like a fluid to fluid exchanger to me. Flat plate exchangers rated for refrigeration usually have fittings for either a welded or brazed attachment for the refrigerant lines. I believe the plate design may differ as well and they are usually rated for 650psi design pressure. You are better off to closely match your evaporator with your load than go with something so oversized. You may have oil return issues due to lack of refrigerant velocity and could also run the compressor a little warm as the suction gas will likely be much warmer with an oversized evap. Do you have a link to the chart showing capacities?
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I agree with your assessment of the "chiller core".
Looks like water to water/oil ?
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I spoke with 32coupe on the phone since my last post. Great encouragement and help for a refrigeration novice like myself. He's sending me a care package with fittings, swage/flare tool, etc. Amazing and much appreciated.
Bronco:
Per your suggestion I'll pass on the glue and stick to old school brazing or refrigeration pressure fittings, thanks.
Here's the chart I found for R410a evaporator flat plate exhanger, on pdf page 12, printed page 10.
https://www.kaori-bphe.com/uploads/editor/files/Catalogue_EN_Imperial-Unit.pdf
The recommended units for 1 ton or 12000 BTU, R410a evaporator are 2.8 x 8"with 34 plates, or 2.8 x 12.2" wth 20 plates.
Exhangers specifically for refrigerant I've found have small inlets on both sides, and are too small for 12000 BTU as the typical small water chiller flow rate is low and pressure loss is not an issue.
I appreciate the warning bout oversizing the evaporator, Bronco. I'd hate to accidentally create a slowly filling oil trap from too low flow rate. I could tilt the exchanger unit to insure gravity oil flow to the return port if you think that's a good idea.
The price of R-410A is stunning; $79 (shipped) for a 2 lb cylinder. Higher than R22.
I wish I could change over to propane refrigerant, but I suppose that's a no-no. The application is ideal for propane as it's right outside the propane water heater closet, and the closet is ventilated for propane use.
One more technical question- how do I determine the ideal or target superheat degrees for my water evaporator/exchanger? I can find this for typical air conditioner AC, computed using air and wet bulb temps but not for a water chiller.
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32coupe suggested this morning that I use flare fittings at the flat plate exchanger, and that made me think again about a suitably sized, 1/2 Female BSP fitting heat exchanger I saw on ebay.
I found some BSP thread, flare fittings and BSP bushings at McMaster.com, fairly cheap.
I ordered 1/2 female BSP brazed plate exchanger (3x8 by 40 plate) for $56. Thanks for the help, and good suggestion, Gary!
The water side is low pressure so I can make 1/2 npt hose barbs fit the female BSP with plastic epoxy (a two part urethane) or Permatex gray gasket maker as thread sealant. As I recall, NPT male fits BSP for that size, just leaky without goop. This is only 12 psi max.
Thanks for the timely warning on over-sizing the evaporator, Bronco!
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Those British threads.......
Do it like they do in India. Take an old rag, dip it in some green paint, wrap it around the fitting and
assemble ....presto bang oh......no leaks !!!
Sound familiar ?
White teflon paste seems to work well for me.
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Hey Gary, Yeah, any serious pipe goop would do on the low pressure side. I just didn't want to frig the refrigeration fittings, re: BSP vs NPT (1/2). No price penalty for the BSP on flare fittings, so I'm happy to do it right. Better than drlling brass plugs and braze in the copper tubes!
Hopefully tomorrow I'll figure out the cause of my in -floor heat (soon to be +cool) 12V circulation pump deficiency; I'm only getting 0.8 GPM flow and it used to be over 2 GPM. I need to correct this for the cooling or the water would get too cold.
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Agreed, just about any pipe dope will work on the water side. On the refrigerant side you will need to use a high pressure sealant rated for refrigerant use. There are several loctite formulas that work. I have always used loctite 554 or leak lock by highside chemicals.
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Thanks for the tip on proper refrigeration rated sealants. I ordered some Nylog Blue which Amazon had so I can get it quickly. My brazed plate heat exchanger should be here tomorrow, and my vacuum pump and gauges Monday.
I got the LG 12000 BTU, 230V window unit late yesterday, test ran it and took it apart this morning for reverse engineering. It's dual capillary tubing instead of a valve for the evaporator. There are no valves for operating as a heat pump. It is really just a cooler, when I peeked behind the evaporator coil I found a resistance heater. That makes it a dual cool/heat unit in Korean/American marketing language. The specs are bogus (high) on power draw, it reads 4.5 amps on my clamp on meter. The compressor is in fact made in China. No BTU rating on it but the model number is so I'll check the specs.
It uses a common 80W, 2 speed induction fan motor, and the wires are marked for high and low speeds. I'll only need the high. The compressor is a single speed 3 wire, capacitor start induction motor, not much to sort out there, just what I wanted.
I will replace their electronics with my own, with a circ pump water flow sensor and outgoing, temperature used to turn off the compressor.
My neighbor is very interested in this project for his (similarly constructed) home, and has offered to get a rental cylinder of nitrogen for me so I can use it for purge, braze, pressure test.
So far, it's looking good, with no bad surprises.
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Yep, can't beat them for simplicity. The capillary setup is what I was expecting you to find.
The more I think about this I don't see any reason you can't just un-sweat the capillary tubes from the evaporator coil and put them together into a piece of 1/4" soft copper, lightly crimp it shut around them and sweat that up. You can then just run 1/4 copper to the HX and have a flare connection there. you would end up having to do that anyway to make the connection at the HX, better off to just leave the cap tubes in place in the AC unit. That is exactly how most ductless mini split systems work, with the metering device in the outdoor unit. You will need to insulate that line well, at least 1/2" wall thickness insulation. It looks like you can also cut the suction line right before the Y joint where the two lines come from the evaporator and use that as your tie in point. As long as the copper isn't an oddball metric size you can also just have a flare connection there. That gets you down to one solder joint or two if you decide to sweat the suction line.
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Thanks, Bronco. Gary also suggested that extending after the cap tubes is commonly done on a phone call. I can see it if insulated well. I got the electronics removed today. I replaced the two PCBs with just two switches for compressor and fan, adequate for testing.
Can capillary tube can be cut with a pipe cutter? My best guess otherwise is to cut it with an Exacto saw blade (super fine, tiny back saw made of stainless steel) while flowing nitrogen out that cut.
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Cap tube needs to be cut with cap tube cutters. Tubing cutters, if they can even close small enough, will collapse the tube and leave a burr inside the tube.. The inside diameter and length of the tube are specifically sized for proper refrigerant flow. You dont want to alter the inside diameter in any way. If you are trying to cut it right at the coil to avoid unsweating it that shouldn't be a big issue.
Your saw will probably work fine but I wouldn't just cut right through it, you could end up with a burr. I would cut around the entire diameter to the point that you are almost through and then snap the cap tube off. That will give you a clean cut with little to no distortion to the tube ID. You can use a fine file to do the same thing. I tend to keep some super small drill bits on the truck to clean out any burrs and just do it by hand or a pin vice can be used.
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I had no idea there was such a thing as capillary tube cutters until you mentioned it; thanks Bronco.
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I'm searching for a chart or table to size the suction line extension (6 foot ) for my 1 ton (12000 BTU). All the published tables I can find don't go that low. The LG unit has 1/2 OD suction line leading to the stock evaporator.
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I would stick with 1/2". 12,000 btu is right at the threshold between 3/8 and 1/2 for 410a.
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Thanks! I'd love to have the reference name. I did find a vendor chart:
https://www.hillphoenix.com/wp-content/uploads/2020/02/Gen-suction-and-liquid-line-sizing.pdf
It shows 1/2 inch for a 6 foot suction pipe for R404a, and since R410a is usually a bit smaller, it makes sense that 3/8 is on the edge for 410.
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I did find a R410a refrigeration pipe size calculator that goes to 0.8 tons online:
https://efficientcomfort.net/asp/LineSetCalc_Web/LineSetCalc_Web.asp
It says 1/2 inch even dialing down to 1 foot and 0.8 Tons, or 1 ton at 94 feet. It won't ever 3/8, so I'm suspicious.
I'll try to find some 1/2 ACR tubing in the area tomorrow.
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3/8 should be fine
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Ebay seller sent me R22 by mistake. Grrr.
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I did find a R410a refrigeration pipe size calculator that goes to 0.8 tons online:
https://efficientcomfort.net/asp/LineSetCalc_Web/LineSetCalc_Web.asp
It says 1/2 inch even dialing down to 1 foot and 0.8 Tons, or 1 ton at 94 feet. It won't ever 3/8, so I'm suspicious.
I'll try to find some 1/2 ACR tubing in the area tomorrow.
Here is a calculator that I use on smaller stuff. https://boxload.tecumseh.com/RefLineSizing.aspx
I used input data of R-410A, Suction Line, 40 degree Evap temp, 105 liquid temp(This should be about 10+ degrees above your expected ambient temperature with a minimum of about 105), 6 ft equivalent length(if there are any bends in the pipe this goes up), and 12,000 BTU capacity.
You can select different tubing sizes and it gives you the velocity, pressure drop, and temperature drop. I was taught and always use 750-2500 FPM for suction velocity and a max of 2 psi and 2 degrees for the pressure and temperature drops.
A very broad rule of thumb as you play around with the variables; your suction temp is generally 10-15 degrees below your desired fluid temp and your desired fluid temp is about 10-15 degrees below your desired load temperature. So, if you want a a 60 degree slab, best case is a 50 degree fluid and 40 degree suction temp. I checked every pipe sizing chart I have and they all recommend 1/2" for 12,000 BTU at Medium/High temperature suction.
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Ebay seller sent me R22 by mistake. Grrr.
Well that was a several hundred dollar mistake. The price of 22 has gotten outrageous. 2 lbs of 22 is a few hundred dollars these days. Been working on a system with 3600 lbs of it for the last few days :o.
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Good to know the Tecumseh calculator is trustworthy. I tried it but didn't know what temps to plug in.
Now I know why the seller was so cooperative. ;) And I thought R410a was bad...
Even with a bulk discount, 3000 lbs of R22 !!! The industrial insurers would squeal over changing an older system R22 to Propane. You could eat some engineering re-certification and special insurance costs for that kind of money. Somebody must be doing it, with that kind of money involved.
Gary sent me a great flare/expander tool kit, found in my mailbox on the way to way to the post office. It looks great, thanks, Gary!
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so what does a 30 lb can of r22 sell for these days?
wholesale? retail? usd?
btw, what does r-12 fetch? bet that stuff is regarded as contraband these days?
inquiring minds want to know?
:)
bob g
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Bruce,
I use a flair kit just like the one I sent you.
Just a tip I do. I don't have the hand strength the tighten the "wing nuts" on the bar clamps to
hold the copper while working on it. I use the sliding bar on the flair tool to tighten the "wing nuts"
I don't know if it was designed for that but it sure works.
Did you get the silver solder to flow out ?
Gary
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Rain the last 2 afternoons has curtailed my copper brazing practice. Soon!
R22 on ebay, around $720/30 lbs plus $50 shipping. Ish.
$24/lb x 3000 = $72,000. plus freight.
The 2 lb R22 containers run $175 incl. shipping.
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Even with a bulk discount, 3000 lbs of R22 !!! The industrial insurers would squeal over changing an older system R22 to Propane. You could eat some engineering re-certification and special insurance costs for that kind of money. Somebody must be doing it, with that kind of money involved.
Propane and Isobutane are a BIG no-no. There is a limit of a few ounces when it comes to charge due to flammability. There are many retrofits for R-22 these days and a couple that I use and seem to work well. This particular system is a liquid overfeed system with a flooded evaporator vessel which does not work well with the retrofit refrigerants as they are blends and all of them have at least 5 degrees of glide. So, for now they are stuck with R-22.
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so what does a 30 lb can of r22 sell for these days?
wholesale? retail? usd?
btw, what does r-12 fetch? bet that stuff is regarded as contraband these days?
inquiring minds want to know?
:)
bob g
I haven't bought any 22 in a while, although my cylinder is almost empty. :'( Last time I did it was about $1100 for a 30 lbs cylinder. I imagine it is higher than that now. On refrigerants 5X cost is about the norm when it comes to mark up. I have heard of guys charging way more than that though. I haven't used R-12 in over a decade. It is still available from wholesalers and I think is still above $1k a cylinder but there just isn't any R-12 equipment around that hasn't been converted to a replacement refrigerant. I have a 50 lbs cylinder that has been sitting in the shop for 10 years. I traded a guy half a cylinder of R-410a for it as he needed some refrigerant in a piece of equipment and he had no use for the R-12, nor did I but did it as a favor. That's just the way it goes, ultimately the retrofits and conversion end up being cheaper over time.
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About a year ago I looked into the price of R-22 and the price was fluctuating from just over $700.00 to over $1,400.00. On the internet from people that try to sell to people that are not CFC certified.
Refrigeration supply companies only deal with people that are CFC certified or, businesses that are licensed contractors. And the suppliers are the best place to purchase refrigerants at decent prices (legally). It’s getting to the point that some suppliers are starting to be cautious selling refrigerants to people that are only type I certified. Some say it’s company policy and I understand their concerns. I was fortunate to get my universal certification back in 2002 and built up a good relationship with my local suppliers.
Be careful buying refrigerants on line from an unknown source. You don’t know what your getting. And here in the US it’s illegal to purchase refrigerants without the proper certification.
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back in '05 a friend of mine who was in the automotive business called me wanting to know if i wanted some r22. a local autoparts chain had ordered or bought what they thought was a remaining stock of r12, it turned out to be r22 and they had a semi truck load of the stuff. i think he resold it to a local refer guy.
he bought 8 thirty pound cans for 65 dollar each.
seeing what it brings now? wow, maybe i should have bought the whole trailer load?
story of my life, day late and a dollar short!
bob g
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I have used several of the "drop in" replacements for r22 and have found
r422 to be the best for what I do. (marine systems) The 2 local supply houses I deal with don't carry 22 at all.
I haven't seen r12 for years. I used "hot shot" for a few units that used 12
but I still have a half a jug of it because the systems I maintain have been
changed out to 134 units.
The industry is , and as near as I can tell, will always be a mess.
R22 was "outlawed" years ago but still available.
R11 was "outlawed" years ago but is in all the "cleaner" products.
I have a jug of r11 that I'm sure I'll never use.
You really have to wonder about the entire situation.
It is illegal to buy refrigerants without a card or license but it looks like
you can buy it on line without either. How does that work ?
Just another case of the left hand not knowing what the right hand
is doing.
410 is supposed to be phased out the next few years. Looks like
it will be replaced with the flammable types that I won't be involved with.
At my age a couple of years and I'm done with all of it except my own junk.
Reminds me of cars. They are supposed to meet fuel mileage standards. But if you pay the tax, epa fine or
what ever its called you can buy a new 800 hp car that gets mileage well below the standard.
I used to say we live in a crazy world. Now it's just stupid. Same old game, money talks.
Rant over, have a great day !
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i haven't done any refer work since the days of r-12
and that with the automotive applications.
i remember back in the mid 70s there was a bb machine gun that was powered by r12 one pound cans! i never had one, but have often looked back at how that added to the ozone problem.
but then again, back in the day, when you had to repair a system, you simply let her rip, changed out the part, vacuum down and recharge, if you had a leak, you just let it go again, fix the leak and repeat the process... r12 was cheap and we had no idea it was hard on the ozone layer.
i recall buying r12 in the one pound cans (might have been 14oz, but we called them one pound can's) for as cheap as 89 cents a can on sale at the local autoparts store.
sure miss working with r12 the systems were easy to repair and i don't know anyone that knew anything like all the stuff professional refer guys know today.
all we cared about was getting the vacuum down for maybe 10 minutes (tops), recharge until the sight glass cleared, and checked the vent for cold. if it got down to 40F or below that was a good job, and down the road it went.
we didn't know "superheat" from an "afterburner" :)
thats probably why there was an ozone hole? :(
bob g
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You really have to wonder about the entire situation.
It is illegal to buy refrigerants without a card or license but it looks like
you can buy it on line without either. How does that work ?
People are selling it on Craigslist. They are not asking for any documentation.
Here it an example:
https://lynchburg.craigslist.org/mat/d/lynchburg-r22-refrigerant/7348275245.html
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Interesting 3000 lb system, Bronco. Apparently German automotive and industrial co.s are going with propane/butane mix to meet their global warming goals. While totally unsuited for some applications like marine, R290 would be fine for my application since the evapaorator/water chiller/brazed plate exchanger is just inside the wall of my ventilated propane water heater(s) closet.
You can get EPA section 608 certification via online open book exam. There are many companies selling prep courses and testing services online.
The ebay sales places require a statement that you are buying it to resell or to give to a certified refrigeration tech. That's a loop hole that makes my small project easier. I waffled as it's irrelevant but decided to do my bit and am reclaiming the measly 20oz in my window unit via the system pump pressure side to vacuumed bottle method. With losses in hoses and hose purges, this is dubious in real value, but old habits of a former AF engineer die hard. Plan B was to make my own reclamation pump from a bare refrigeration compressor, but it's just not warranted for this small project since the high pressure capture method can be used.
I'll probably get my 608 certification if I decide to do any more refrigeration projects after this one. I've long thought about a dual- remote compressor, freezer/refrigerator project with no motors or fans in the house, only linear direct 12V circuitry and dual plastic fiber thermostat signals). That could replace my sealed combustion propane refrigerator.
I tried the brazing rods that Gary sent me. As he suggested, I used the smallest tip I had for my oxy/acetylene torch. It was easier than sweating water joints with mapp gas, no messy bubbling flux, and it wicks into the joint and flows at the right temp just like normal copper sweating. I did a 1/2 ID water type copper fitting, and used Gary's nice swager to fit 1/4 to 1/4 tubing. Both were easy and I like the precision of the small flame when thinking about fittings near plastic bits and in tight quarters. Thanks, Gary, the 15% silver brazing rods work like a dream.
My two test joints, a 15% silver brazing rod and tiny torch tip below.
Now I have a fittings project; I need to adapt my inert gas regulator (argon/nitrogen) hose to the refrigeration gauge set hoses for purge/pressure test/flow.
Bronco wrote:
"So, if you want a a 60 degree slab, best case is a 50 degree fluid and 40 degree suction temp. I checked every pipe sizing chart I have and they all recommend 1/2" for 12,000 BTU at Medium/High temperature suction."
Good to know the rule of thumb. So for a 70F slab, 60F water, 50F suction temp. For in floor cooling, too cold water will cause condensation issues at the manifolds.
More project goodies today on the UPS truck, I hope.
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Yes, that 15% stuff flows like butter.
It's amazing how little it takes and what a beautiful welded joint you end up with.
Yours look as good if not better than mine !
Glad to help Bruce.
Can't wait to see how your project turns out !
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In the plumbing industry, over 30 years ago it was called silver soldering. Oxygen & acetylene is the way to go. In upstate NY (the Lake George region) all underground pipe had to be K Copper and it had to be silver soldered. From 1985 - 1992 one of my primary jobs was running underground supply lines from 3/4” up to 2” When silver soldering 2” pipe, lots of gas is used. In the cooler days it got pretty toasty in the trench. I stayed warm when other were complaining about the cold. But in the summer months it was brutal.
I’m not sure if it was mentioned, it’s best to purge all refrigeration lines with nitrogen before brazing.
BruceM, the joints look good.
When you do enough joints you will get pretty good at them.
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I like brazing with oxy/acetylene on a neutral flame; it's a no-stink clean burn after the torch is lit and adjusted, and the 15% silver brazing rod was also a delight- no nasty flux fumes. It flows around and into the joint as if it had flux.
It's been raining all afternoon, lightly. We sure need it. I'm still missing a few things but I did get the vacuum pump and gauge set.
I was able to make a 1/4 hose barb to 1/4 flare adapter with some parts Gary sent me, so I'm good to go with the Nitrogen.
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Be careful buying refrigerants on line from an unknown source. You don’t know what your getting. And here in the US it’s illegal to purchase refrigerants without the proper certification.
X2 I have heard stories of guys working on systems and finding that someone had put in either a blend including propane that mimics r-22 that was labeled as R-22 or some of the "retrofits" that are not legal here in the US due to flammability but can be bought online. Brazing on a system that has had a flammable refrigerant in it but has not been thoroughly purged with nitrogen can be a dangerous thing. There is a lot of fraud and deception going on in the trade because of the prices these days. I only buy from the distributor and the one I use is also one of the largest manufacturers in the US so it comes straight from their factory to the supply house.
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Good to know the rule of thumb. So for a 70F slab, 60F water, 50F suction temp. For in floor cooling, too cold water will cause condensation issues at the manifolds.
That would be best case scenario. You will probably find you are closer to 15 degrees difference between each heat exchange. Depending on how the AC unit was engineered, cap tube sizing, and your slab load I don't think you will get any higher than about a 45 evap temperature, probably more like 35-40 degrees.
Nice job on the brazing. I have seen some of the young guys that can't make joints that nice after a year of "practice".
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Bronco-
How does the capillary tube length affect evaporator temperature assuming a modest deviation?
An elderly disabled woman friend of mine in Cornville nearly got fleeced by her HVAC service provider of years a couple months ago. Her guest house AC didn't work. They had removed a breaker, then when called this spring about it not working, they claimed she's have to replace the condenser unit. I convinced her to get another opinion, that guy was honest, found the dangling wire with no breaker, replaced it and it ran fine. The HVAC business has the same problems as any other profession. Too many humans are sociopathic or crooked. Makes you appreciate the good ones!
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Bruce:
at the risk of highjacking your thread...
but thought this might be as good a place as any to get this question answered.
what kind of tech would one look for to charge an ammonia system, one that has been newly constructed and is located in a non habited building?
what does it entail?
thanks
now back to your regular scheduled programming ,,, :)
bob g
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Bronco-
How does the capillary tube length affect evaporator temperature assuming a modest deviation?
Capillary tubes flow a certain volume of refrigerant, it will vary slightly based on liquid pressure but not a whole lot. Depending on how much load you are dumping into the heat exchanger you will either be above or below the design parameters used when the cap tube was sized. I am thinking you will probably be below due to the lower temperature delta in your water system vs the forced air evaporator it was sized for. Not a problem, you will just run a little cooler on the suction side.
I haven't sized a cap tube in a long time and likely if I had to would track down a chart or calculator these days. The gist of it is that the inside diameter and length determine the flow rate. Alter either and your flow will change. The smaller the ID or the longer the capillary the lower the flow.
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what kind of tech would one look for to charge an ammonia system, one that has been newly constructed and is located in a non habited building?
what does it entail?
thanks
now back to your regular scheduled programming ,,, :)
bob g
Bob, you are going to need to find an industrial refrigeration guy, and one that knows ammonia. There aren't many of us left. Ammonia fell out of favor long ago except in heavy industrial applications due to it's extremely hazardous nature. All of the guys that knew ammonia and trained guys my age are long retired or no longer here. There wasn't really enough ammonia work around by the time the younger guys came up behind me to train them on it. I only have one ammonia account left.
Ammonia is enjoying a little bit of a resurgence in popularity due to it's environmentally friendly properties so hopefully more guys will learn how to work with it as other than the dangers associated with it is a fantastic refrigerant. These days noone does direct refrigeration with it as the safety and monitoring systems necessary are cost prohibitive but it is getting popular again in chiller systems where it can be contained in a room with emergency venilation and sealed from or away from the building it is servicing.
Ammonia can be fairly hard to get sometimes as it has become somewhat of a specialty item and not many suppliers want to stock it due to it's hazards. It has become a federally regulated substance as well. I have to file paperwork when I purchase it and sometimes the supplier has to come out and do a site inspection to verify that there is actually ammonia equipment onsite and make sure there is a safe storage area for it. I used to just go pick up however much I needed and it was no big deal.
A good starting place for a service guy is to contact the equipment manufacturer. Most of them have a network of service companies that they can recommend. If you can track down the installing contractor they may have a service department. It is a crap shoot sometimes though. Shoot me a PM with some info and I will see if I can give you a hand.
When you say charge, is this something that has been built but never commissioned or was there a failure and the ammonia released?
For the sake of Bruces water chiller thread we can discuss in PM or maybe in another thread if it is of interest.
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The IcyBall is a wonderful device, and I've dreamed for some time, of re-creating one out of "parts" .
But I don't have the skills to pull it off, but such an elegant design.
http://www.crosleyautoclub.com/IcyBall/crosley_icyball.html
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No worries. I've been using an ammonia refrigerator/freezer for over 10 years so am interested.
While my Ammonia fridge was still under warranty, it sprung a leak and quit cooling. I had to replace the whole ammonia unit with a replacement myself, quite a chore. It's been fine since, zero noise and zero load on my battery bank.
I got the refrigerant reclamation tank late today and used the pump and gauge to put a vacuum on it. It got dark and rainy so I stopped, but will continue that tomorrow. Hopefully I'll make some real progress tomorrow; like getting the window unit evacuated and the stock evaporator and blower removed, valves installed, etc.
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I was able to capture 1.1 lbs out of 1.25 lbs faceplate charge (20 oz) of R-410a using the 12000 BTU window unit compressor as the "recovery pump", with the well evacuated recovery bottle in a bucket of ice water connected through the gauge to the high side bullet fitting.
I had gauges on high and low side via bullet piercing valves. They worked and didn't leak. I'll remove them and silver braze the holes after adding Schrader valve stems. If I was doing it again, I"d skip the high side gauge and second hose, and hose direct to the tank, and watch the low side for pressure going to zero. That was the limit for my pump, with the high side about 105 psi. It just couldn't do more. About 3 minutes of compressor and fan run time. I could have stopped sooner but kept hoping it would pull a vacuum. Once low side was 0 psi, it could do no more, so I closed the tank and shut down. My vapor pressure equalized in the system at 50psi after it sat.
I think that's not bad for no recovery pump. I don't know if a refrigeration compressor will do any better. I've read most recovery pumps will pull low vacuum, while still delivering high pressure to the tank. That's impressive.
I was able to remove the stock evaporator and cut the evaporator side motor shaft off after removing all the plastic and cast bead board. I re-routed the high and low side pipes as I want them both coming in compressor side. The photo shows the unit stripped down to it's condenser unit function. The condenser fan shroud was shifted out of the way for some brazing of new schrader valves, which comes next. The brazed flat plate exchanger is in the rear of the pan, and the capillary tubes are on the left of the pan.
The electonics have been removed and replaced with one switch each for fan and compressor. It was a breeze to reverse engineer this unit's electronics, since the motors are induction type.
I'm beat but happy about the amateur, low budget recovery.
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Looks good !
I was expecting the plate cooler to be much larger.
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Back on the project today. The refrigerant to water exchanger is installed and plumbed so that it drains any liquid and oil to the outlet, and it's slightly downhill all the way to the condenser unit. You can see the capillary tube coil near the insulated exhanger. I had to make one new end, by cutting the tubes and brazing them in a slightly flattened 1/4 tube. The service valves are now brazed in on the "stripped to condenser unit" (thanks, Gary!).
I am included a picture of the small nitrogen bottle my neighbor rented for me. Paperwork says $6 rental, $18 for the gas. I'm using a cheap argon flow type regulator/ valve. Just enough to have the ball spinning and not lifted seems good by the finger on the end of the pipe method. I can either slide the 1/4 hose on copper and clamp, or use my AC service valve adapter which I made with one of Gary's valve stems soldered to a brass hose barb.
Outdoors, I picked a spot and leveled it with some sand, and laid some 8"block caps. I wanted to raise it just a little to avoid flooding it when we get torrential rains, but keep it low enough for a downhill run from the evaporator.
I've got to do some sheet metal work for a protective case, otherwise, I'm ready to hook the outdoor unit.
The stock housing has zero protection for the condenser, so I've got to do some redesign for a ground mounted unit.
We're having a new heat wave so I'm hurrying to get it hooked up for testing.
Best Wishes
Bruce
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When you plumb it to your floor make sure the slab coolant and refrigerant flow oppose each other. You want the warm fluid coming from the slab coming in to the refrigerant vapor end of the HX.
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I appreciate the reminder, Bronco. I did plumb it for opposing flow direction, per the heatex mfgr recommendation. It's all plumbed into the house floor system in the photo shown, I just left out all the other plumbing in that closet! The flare connections Gary recommended made the tubing connections to the heatex easy.
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Bruce,
I would rotate your HX so the unit is vertical with the cap tubes at the bottom.
You MAY need an air bleeder in your water line as well.
Gary
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Thanks for the note and the phone call, Gary. i'll have to revise my refrigerant flow; for others benefit I'll summarize; most water chillers (Gary sees many on boats) have refrigerant coming in on the bottom, with return off the top, to maximize vapor only return to the compressor. The liquid on the bottom is "boiling" into vapor due to the low pressure.
The air bleed for the water line is also an excellent idea.
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There is a dense technical manual on AlfaLaval's web site regarding the use of their brazed flate plate exhangers for water chillers.
https://www.alfalaval.com/globalassets/documents/microsites/heating-and-cooling-hub/technical-reference-manual-refrigeration.pdf
On page 65 of the pdf document (printed page 58);
''3. Flow arrangement.
3.1. The one-pass BPHE.
3.1.1. Evaporator.
♦ The evaporating fluid is normally flows upwards and the
heating media flows downwards.
♦ Downwards evaporation is not impossible but needs a
comparably high channel and low nozzle pressure drop
to distribute the liquid properly.
A high nozzle pressure drop means that the fluid will
have a maldistribution from the first to the last channel.
A low channel pressure drop means that the liquid will
not distribute properly over the channel width.
Downwards evaporation in BPHE has been little studied
and tests should be made before an installation is
made. Expect a fairly large capacity reduction compared
to upwards evaporation.''
This clearly indicates that bottom up flow for the refrigerant in brazed plate exchanger water chillers is the preferred engineering configuration, as Gary noted , and I'll switch to that configuration. I'm very grateful for his sharing his water chiller system knowledge. i'm grateful Gary caught this before I charged the system.
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I got a few things done on the project, but now must wait for the sun to go lower or the clouds to get thicker; it's too damned hot and bright for me to do the copper hookup to the condenser unit. The heat reflecting off the west facing shop wall makes me think I may have picked a poor location. I'm going to proceed with it for now.
I reoriented the brazed plate exchanger/evaporator per Gary's advice. I finished the window unit case modifications to basically reverse the case, with a solid rear panel and recessed condenser fins with hardware cloth protecting them from curious dogs and goats. The cover has been modified so that it screws to the chassis, and is a lift off design for service. The former window AC base or chassis has been shortened to allow the case to overhang the condenser coils. I changed the orientation so that the condenser side is protected from hail. It now faces north. I did run the fan with it in this position to see if this might be a problem, and I think it's OK.
Clouds are getting thicker so I'll try to make the last copper connections.
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Finished the copper connections but alas, on pressure testing I found that the BSP adapater bushings were leaking at the stainless steel BSP female fittings of the heat exchanger/evaporator. So much for Nylog Blue and Chinese made BSP threads...
I also found the brass 3/8 flare/1/4 NPT male fitting was dented, so I'll be heading to ACE this morning to get a replacement.
Rectorseal Tru Blue is listed for refrigeration and stainless, and ACE carries it, usually.
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Thursday, after more fiddling with the fit of the alleged BSP adapter bushings into the female 1/2 BSP thread heat exchanger, I noted that there was little improvement over 1/2 NPT. No non-setting pipe dope will solve that problem, so I did more research on silicone/RTV compatibility with refrigerants. I decided to use my old favorite for damaged and old leaky fittings, Permatex Ultra Grey. The worst case with RTV is normally swelling, which is a non-problem for pipe thread sealing.
I got it in and tested at 50psi nitrogen a few hours later. No leaks detected. Rain and wind encouraged me to wait until Friday to test again at higher pressure. I did that this morning, first at 100 psi, then 200 psi. All is well, so far. I'm evacuating the system now, will let it run for a few hours, then start the R-410a charging.
Gary suggested by phone that I might find it easier to just sit the brazed plate heat exchanger on the floor, on foam. A very helpful suggestion, and I strapped it upright to a board with a piece of styrofoam board under it. So hookup was a little easier, as was air burping, this time.
I purged the water line hookups and have confirmed circulation flow at 2 GPM , with the flow sensor I'll be monitoring via some custom electronics to shut down the compressor to avoid freeze damage to the brazed plate exchanger. High hopes!
Bruce
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Looks good Bruce !
Looking forward to seeing the charge numbers.
......................
Nothing to do with your set up, just another example of what's out there.
I worked on a SubZero drawer freezer today (evap replacement) and noticed
the the evap coil has the cap tube in the top of the coil and the suction right
next to it at the top. So in this case the liguid is sprayed in the top with the tubes
running horizontal so the gas falls down half of the tubes then returns through
the remaining tubes to the top. Interesting setup.
I have replaced many of them through the years and never gave it much thought
untill your "chiller" project popped up.
Just another "way of doing it".
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Slowly sneaking up on the charge:
90F Outdoor temp
High Pressure: 390 psi
Suction: 90 psi
Superheat: 40F (Suction at compressor 72F minus Sat. Temp per low side gauge: 32F)
Water cooling differential at 2 GPM: about 6.5-7F Less than I'd like- goal was 10F.
Got rained out, so will have to continue tomorrow.
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What were your fluid entering and leaving temps?
What was your liquid line temperature?
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Water temperatures 71F in, 64.5F out, at a measured 2 GPM.
The actual temperatures are likely a few degrees higher, but I used the same digital thermometer probe on each rubber hose, with an foam tape wrap, so the measured delta temperature is accurate.
I'll do better tomorrow at getting calibrated temperatures, and perhaps some house floor temps near one of the manifolds.
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I would bet you are within a few ounces of a full charge.
This crowd never ceases to amaze me. A guy with no real experience in
the field with a little research and encouragement can pull off building a
"home brew" chiller system. I don't care what anyone says thats pretty impressive.
There is a lot more there than meets the eye.
I'm just happy I could help the little I did.
Bruce, my hats off to you sir !!
Looking forward to seeing your final numbers.
Gary
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can you throttle down the flow rate a bit?
maybe run a test at 1.5 gal/min?
as a guy that isn't conversant with the finer points of refrigeration...
i would ask how much cold is being returned to the system from the heat exchanger
in other words, is it near what is expected from the system in its original application?
just spitballin,
if the return temperature of the evaporator was for instance 45 deg F in the airconditioner as designed
and in the new application it is say 40 deg F, then i would think i am not getting all the cold that is available.
realizing that it isn't cold you are making but rather heat that is being removed, it is just easier for some of us to think of it the other way.
by slowing the flow, maybe you are able to reject more of the heat of the slab water to the heat exchanger?
something to think about, and maybe it might have application here.
years ago, the big cam cummins 855cu/in ntc 400 had 2.5" radiator top and bottom hoses, and a water pump that moved a lot of water.
then the big cam 2 or 3 came out and it used a reverse low flow system, with 1" upper and lower hoses, and dramatically reduced flow from the new pump design... the water moved slower so it could use smaller hoses and it did a better job or rejecting the heat of the same 400hp engine in the same class 8 truck with a 80k lb gvw. none of us thought it would work, but it did.
changing from the way things had been done to a system that used 1" hoses and a tstat the size of a silver dollar was nothing short of amazing.
so i am wondering, maybe slow the flow rate down, giving the water time to shed its heat to the system?
thoughts?
bob g
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Bob,
I'm sure Bruce knows slowing the flow will remove more heat but at this point I believe it is still just
a little low on refrigerant. Good thinking though.
The head pressure is close to the upper limit in my opinion but the low side pressure is just
a little low.
I do know Bruce is reading the amps on the compressor while charging so with that and
pressure/temp readings he should be able to get the charge spot on. Then if the TD across
the "chiller core" is still too low that would be the time to think about slowing the water flow.
Unfortunately because it's a home brew project there are no "factory specs". It's a guessing
game as far as the numbers go. (to an extent....the refrigerant properties and compressor
amp ratings are known)
I could be wrong on all of this......maybe the suction pressure SHOULD be lower . But I still
think geting the suction pressure up a little without driving up the head pressure up much
more would be the palce to start. Bruce could always remove a little freon if the water temp
numbers start to rise.
We will see........
I hope Russell chimes in on this because I believe he is more technically knowledgeable than I am.
Gary
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The help and encouragement has been a huge boost for me. Good to see you chiming in, Bob.
My water cooling/power consumption target is 12000 BTU which calculates to a bit over 10F degrees of water cooling at 2GPM. Slowing the flow in this sort of closed loop system would help if a lower target water temperature was needed, but otherwise, no help with actual BTUs of cooling delivered. The water temps I'm getting are OK at 2 GPM. I don't want to go below 58F water, or I may get condensation at the PEX manifolds. Another reason to not just through lots of BTUs at this system.
The suction temp at the compressor was 72F, I'll have to measure it at the heat exchanger. If it's about 10 degrees colder there (as normal for remote compressor/condenser setup), it's very close to the outgoing water temp...so the exhanger is doing as it should, but I'd like a few more BTUs.
I'll see what water chilling performance I can get tomorrow. My pressures are a little low for R410a, and my superheat is quite high, both pointing to needed a bit more refrigerant needed, though superheat targets may not be the same for a water chiller. Still, I hope it may give me some performance improvement.
Normal use is with an air evaporator, with a colder return, thus lower superheat value. The water exhanger throws a wrench in the normal values- I haven't been able to find a good tech reference for that part of the design, so I am just going to measure the delta water temperature as I add a bit of refrigerant, watching pressures and monitoring amperes.
The capillary tube adjustment for the brazed flat plate exchanger/evaporator is another performance impacting issue I don't understand well enough to do, yet.
I will take a liquid line temperature tomorrow. I didn't today because it's not needed for superheat calculation and supercooling isn't recommended for capillary tube systems.
I'm hoping for sunny and hot tomorrow!
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Hey Bruce I was reading what you were saying about threads and sealing issues. Are you comfortable that your fittings do have the threads you think they do? I don't know if it's the same over there - but here there is often confusion, especially in hydraulic or pressure systems, with JIC threads being mistaken for NPT
Similar threads but different sealing systems. If you wanted to google JIC (Joint Industry Council so another SAE thread) I'm sure there'd be endless detail online
Sounds like a fascinating project. Well done
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Sorry I have been absent on this Bruce. Been pulling 16 hour days keeping up with the heat and working on a chiller repair.
From the calcs I ran with your existing temp differential and flow looks like you are doing about 6500 BTU of sensible work. With a chiller since there really isn't any calculable latent work being done in your setup I will just stick to sensible loads. That window unit is specified at 12,000 btu total load and I would guess at least 15% of that would be latent heat so it won't surprise me if at best you get around 10,000 BTU out of it. That should still get you right at your target of a 10 degree TD.
With the evap temperatures you are running I would expect to see a higher suction pressure and you are bouncing right against the upper limit of where I would feel comfortable on discharge pressure. I would try to stay below 120 degrees condensing temp on the discharge. Can you monitor your liquid line temperature a few inches from the condenser outlet? That will give you an idea of how much subcooling you are doing. That will help give a better idea of how long the liquid is spending in the condenser for troubleshooting.
I think you are going to find that the cap tube is limiting your refrigerant flow as I would expect a lower differential between suction and discharge on a 90 degree day. That unit does have some constrains as far a condenser size though. Just for troubleshooting sake before you get too far with the refrigerant charge could you throttle the water flow to 1.5 gal/min and see what it does to all of your measurements after giving it 5-10 mins to settle out? I think that may help with your superheat at the compressor but will also be a good set of data points for comparison to 2GPM.
I do think you are still a little shy on refrigerant but I think the cap tube is going to limit you. You will likely end up having to find a happy medium between TD and flow rate to control your head pressure which is ok. Any idea how much refrigerant you have in so far?
Here is part of the chiller setup I am working on. ;D New evaporative condenser and storage tank. Should be done in about 2 weeks.
(https://listerengine.com/coppermine/albums/userpics/10020/normal_tower.jpg)
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Hey Mike. I'm quite suspicious that the McMaster.com 1/2 BSP male to 1/4 NPT female bushings I got are the wrong parts, or that the female threads on my brazed plate exchanger were out of spec for BSP. It was the BSP to BSP that were not a proper snug fit. No problem on the NPT side fitting the flare connectors.
Fun to see that monster of a chiller, Bronco, and I appreciate your thoughts. I'd love to be able to adjust the evaporator refrigerant flow restriction to see how that affects water chilling BTU performance; something like a high pressure needle valve, but I've not found such a beast. Capillary tube shortening is doable but I'd need a reclamation pump and would need to add a flare coupler. A lot of time and work for each iteration... not ideal for experimentation.
Multiple rain showers through the night, and heavy cloud cover this AM so I'll just have to wait and see. Cool temperature performance is not very helpful when the intended use is for days in the high 90's F during our wildfire season in June and July.
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Hey Bruce,
Could you slow water down with one of your swing valves ?
In a perfect world an expansion valve on the liquid line at the HX would be the way to go.
Then you could adjust the superheat at the expansion valve.
When I went to the supply house the other day I priced one, about $180.00.....
They will build them in house with Sporlan parts.
I looked online and they are alot less but I'm not positive which one would be best for you.
With that said I would try to slow the water flow.......
Gary
Everyone seems to be in agreement that the head pressure is close to its upper limit.
Like I said when we talked the company that builds systems locally runs them harder than
that but I've never liked that but hey what do Iknow ??? He will run them around 450 but at
point the compressor will draw max RLA......in an ideal world the RLA should be under tag specs
for RLA.
I wouldn't run the head over 425 and at that point I would keep a close eye on amp draw........
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Hey Gary,
Yes, easy to slow the flow by existing ball valve restriction, though I don't see the value in doing so; the temperature is suitable if a few degrees high, I'm just lacking BTU performance I was shooting for.
I'm presently seeing only 4.8 amps or 1104 watts.
This unit is rated for about 5.8 amps/1350 watts.
So by increasing refrigerant or increasing refrigerant flow at the evaporator, I hope to increase the amps and squeeze some more BTU out of it.
I'm not sure about TXV type valves (regulating evaporator refrigerant flow based on evaporator pressure and outlet temperature) for water chillers. Maybe Bronco can tell us if they are commonly used in that case, and what the temperature of the evaporator outlet of a chiller might be for an R410a system??? One problem being I think most chillers would be shooting for much colder water temperatures than I am. 60F water at the house manifolds is about as low as I'd dare go, so a few degrees below that (57F) coming out of the BPHE would be the lower limit, and anything up to 72F is OK.
A TXV valve might be a good, if spendy, solution. I did find small hydraulic needle valves but I think buna-n seals are a bust for refrigerants.
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Yes, txv valves are on the ones I see. The thing is they have a bulb that goes on the suction side
and the txv will "adjust" the charge as its running to keep the suction side "cold line" where it needs
to be. That is why with a txv you adjust the charge by subcooling rather than superheat. (I think I got
that correct) Yes, most are 410 units. And the txv valves are adjustable.
I don't think the "needle valve" is a good idea. Don't think you could ever get it right. You are probibly
talking about an adjustment of a few thousands of an inch to swing one way or the other.
You amp measurements.....is that the compressor alone ?
I would try playing with the charge just a little to see how close you can get the suction to
where you want it without running the head and amps too high.
On an air unit I always look for coil saturation. On a chiller you only have the td across the
core to go by. (Plate in your case)
And yes slowing the water flow will change your readings. More heat loss.
Maybe try slowing the water first to see how much the guage readings change.......
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I didn't realize that the TXV's were adjustable. That makes them very appealing for getting the best performance.
Much more appealing than diddling about hacking cap tubes. I agree, a needle valve is really not very practical.
I'm waiting for it to warm and clear up; there's still lots of clouds. It's only 82F at 11AM.
My floor is 72.9 degrees this morning, room air temp is 74.1, so only 1.2 degrees between floor and room air (head high) with 24 hrs to equalize.
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You have many avenues to go with.......
For simplicity sake play with the water flow first....see what that does.....
Then play with the charge ..........it's a small system.....I have seen where when
they are as close as you are an ounce or two of refrigerant will chance things
considerably.
After all that go to the txv.........the nice about that is that with the txv you could
probibly get the head pressure in the 300 to 325 psi range......the compressor is
not heavily loaded and running much cooler and you are still getting coil saturation.
With said......I only remember adjusting a txv a time or two. They work great right
out of the box....they allow much more leeway on the charge parameters, the txv does
the job !
The txv comes in flair or weld fittings. I have done both but recommended the flair type
simply because you keep the heat away from it.
They also have a bleeder type . It's the way to go.....if you look at txv's you will see them and what
they do
I would think any 12k btu txv for 410 would do the job..
Over and out !
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just asking because i want to learn too
does txv = expansion vavle?
is it basically what is or was used on automotive systems?
we used expansion valves back in the r-12 days, (no idea what is used today, i got out of the automotive a/c business after r-12 went out) and some of them were adjustable.
my belief, right or wrong, was the capillary tubes were simply a move to reduce costs, as they worked and reduced the need for a more expensive expansion valve.
also is there a reason to run such high head pressures? a benefit to the system?
i mentioned the reduction in water flow in order to get more time to remove the heat from the water flowing through the heat exchanger, rather than running higher pressures.
intuitively it would seem to me that if i could get better heat rejection by adjusting the water flow, and reduce the head pressure, the compressor wouldn't have to work as hard? but then again maybe i am way off base, maybe there is a need for having more refrigerant in the system and running higher pressures?
if such a system could accomplish the goals set out, and run with a partial charge, with pressures like 40psi on the low side and 150 psi on the high side on a hot day, i would be tickled.
does it have to do with needing enough charge or refrigerant in the system to return the lube oil to the compressor?
there is a lot for me to learn, and i am very interested in this project! so hopefully you guys don't mind me asking a few questions along the way.
bob g
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Hey Bob,
Yes, txv = expansion valve
Yes, older cars had txv's and the cap tube does a similar job for less money.
I don't remember the older systems much but as I said in an earlier post the
txv's I'm around today are adjustable and with that you have a broad range of
settings to play with. With the cap tube you got what you got.
Yes, adjusting water flow will make a definite difference in system performance.
The difference in pressures is because of the types of freon. 410 runs at much higher
pressures than 12 or 22.
Don't know if any of this helps . And I'm the first to admit that I don't know much.
At lot of variables at play here.
If I had to guess in this case I would think a restriction in the system High head , low suction.
Only the cap tube could do that........cap tube too small or too long . I am not a designer so
can't help with that.
Gary
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Not very hot and highly variable sun today but I did some experimenting anyway.
84F with occasional 90F during sunny stretches.
I managed to get 11.1 degrees of water cooling at 2 GPM, so my performance goal is now met, though the high pressure is a bit higher than I'd like when a get a sunny stretch.
I started with low pressures, both high and low side, and crappy performance. As I kept adding in refrigerant in sub ounce increments, pressures slowly rose and so did water cooling performance. It never stopped doing so but it took a long time to see the water temperature drop further, but it did, after some minutes.
Pressure on the high side is now above where I'd like to be when the sun comes out and it gets hotter. I think this indicates that I should get a TXV valve, or shorten the capillary tube (which I'm less interested in), so pressure could be lower.
Here's the data:
High Side:415 psi cloudy to 440 sunny (122 Saturation temp)
Low Side: 128-132 psi (45 Saturation temp)
Suction temp near evaporator 68F
Liquid line temp a foot before capillary tube: 109F
Superheat: 23F
Subcool: 13F
Running amps: 5.8 (full specified running amps for compressor and fan) with sunny at max pressure 440psi. I forgot to measure fan separately. It's less than 0.3A I need to recheck this with my RMS amp meter; my clamp on meter was showing steady low amps until I moved the wire deeper in the meter hook, and it gained an amp. So my amps checking was crap due to clamp on meter unreliability.
Water flow rate 2 GPM
Water temp in: 67.6F
Water temp out: 56.6F
Delta temperature: 11.1F
One thing I noticed is no more frost on the capillary tube. A little sweating but that's it. At the higher pressure it's no longer flashing in the tube. A good thing; the flashing is happening inside the BPHE where it should be.
I can see the value of a TXV for lower pressures and better efficiency and will look into sourcing one, but I'm in no hurry now as I have met the goal and can afford to remove a little R410a to get the high pressure down 10 lbs without screwing up performance much. I stopped adding tiny burps of liquid when the time to see improvement took minutes, and improvements were diminishing. I need to do some more measurements on cooling the house. I ran out of sun before I could start that process; I want to monitor incoming and outgoing water temps plus slab temp over about 4-5 hrs of running (my intended use, to use my sunny day PV surplus).
I'm very happy with performance as it is, but would be glad for advice regarding my high side pressure. When the temperature rises, it's a bit much by my references. But it really does work best like this.
Suggested online sources for TXV's would also be appreciated.
Best Wishes,
Bruce
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It definitely looks like the cap tube is limiting you. But, my math shows you in the neighborhood of 11,100 BTU of heat removal which isn't bad at all. I definitely don't like that head pressure but with the small condenser in the window unit it isn't terribly surprising. That chiller is taking a lot of load right now. Maybe run it for a couple of hours and see where it settles out. I would bet your temps come down some more and as the slab cools a little your head pressure will as well. I would probably shoot for about 10 degrees of subcooling and a 10 degree td on the liquid side but that would be when the slab is down to operating conditions. You can control the load on the chiller by adjusting your water flow. Maybr try it just to see what it does with your head pressure.
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My local builder would be happy with that.
Amazing isn't it ? Those small systems are touchy......doesn't take much.
Shade on the condenser will make a BIG difference . In Florida as much as a 20 degree difference.
Hard to believe but I have proved it many times.
You might try letting out a tiny amount of gas. You may get the TD closer to 10 degrees
and relieve some of the head pressure.
Considering what you are working with I think you are about as close as you are going to get.
Try to get better more accurate amp readings on the compressor alone. This will be your most
critical thing to watch at this point.
And yes as the load (slab) temp drops so will the temps and pressure in the system.
And........GOOD JOB !!!!!+
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I had a celebratory tequila and water on ice for spending so much time near running motors but getting the job done. So now I'm a bit goofy.
I think my location for the condenser unit sucks- I see a big rise in air temp when the sun's heat is reflected off the shop and garden shed walls. Good protection from hail, but I'd be better moving it further from the building. And perhaps adding both shade and evaporative cooling!
The existing fan has a circular rim designed to spin condensate from the base pan up into the condenser. Normally the evaporator would provide that distilled water. No rain water here in June or the previous months, so hard to supply soft water for such a process, though is could be done.
I don't want to reduce the water flow rate water as the chilled water temps must remain above the condensation point, which would cause mold issues at the manifolds. Today's temps were about as low as I can go. Normally, this approach is only for supplemental cooling, because of that limitation.
I've got quite a bit of addition work to do for control electronics, and power to the unit (just an extension cord jury rigged for 230V now), and line protection. But it sure is great for morale to see water chilling at planned levels. The return water temps today are the lowest I would use cooling for. Normally opening windows at night suffices and the superinsulation plus slab and wall/tile mass lets me ride through the next summer day. I only need cooling for smoke events where I can't open up at night.
For my intended use period, evap cooling could be VERY helpful; 20 degree air temp reduction is common in June as humidity is perhaps 7% during the day when I'd be running the cooler on PV power. So perhaps I need to move the the cooler, put a shade cover over it and think evap cooler pads in the air inlet fed by my well water.
I was surprised that the air volume through the condenser is not very high. It's just a bladed fan, not a squirrel cage blower as was used on the evaporator side. From what I saw today on high pressure PSI variation with temperature, there is a lot to be gained from lowering temperature. Pity I can't run it at night, when air temps are reliably 65F ! Then I'd have to add a pump to INCREASE water flow rate.
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Bruce,
I am so happy to see it work for you.
I went back and looked at your numbers and I do believe you are just a little over charged.
I try to run the suction side on most 410 units just under 125 psi and the guage evap temp
around 38 to 42.......on a 80 + degree day . I wasn't sure what the numbers would be because
of the build changes you made but they look like what I see in the field on air to air and water
to air units.
Funny how some things get lost in translation.......if we knew the cap tubes were frosting it
would have been a direct sign of low charge.......but hey, you know now !!
I think I'll have Knob Creek Whisky Sour to celebrate for you .
Gary
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I looked at some websites, but haven't been able to find a 1 ton R410a TXV. They are all for larger units.
If I move the unit, that would be the time...
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Bruce,
I will make a couple of phone calls tomorrow and see
what I come up with.
I did talk with the local supply house when this project first
started. They build them in house. I remember my friend that works
there said he would have to order the body as they didn't have
one in stock.
I'll get back with you tomorrow afternoon.
I have a couple of other places I can call as well.
Gary
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i have a question for those that calculate this stuff
a hypothetical system, the names have been changed to protect the innocent :)
say a system moves the water at 2 gallons per minute and drops the water flowing through it by 6.5 degree's F
do we use the formula ... 500 x gallons/min x temperature change
if so then in this examples (500 x 2)x 6.5 = 6500 btu's?
if this is true
then would the same system running at 1.5 gallon per minute and a 10 degree change would work out to (500x1.5) x 10= 7500 btu's?
is this basically how you determine an efficiency curve for the gallons per minute through the exchanger?
the reason i am asking, is i had planned on a similar system as Bruce but using the engine driven automotive compressor on the s195 trigenerator to cool a water loop in a set of cast iron radiators within a small superinsulated home.
this is the first time that i have seen an actual build in process, even if it uses some different parts.
bob g
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would any of these be small enough?
https://www.rparts.com/index.php?cPath=84_13_24_68&osCsid=ba5nl9i8m4pavjk6p0k0f0nfr5
i haven't followed this company in years, but they used to make complete kits of parts to make small systems for the boating industry and were geared toward diy but made a change when the epa got more sticky
bob g
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Bruce,
I would try the evaporative cooling on the condenser coil. To test just drizzle water on the
coil. In the end you could use a solenoid that turned on water when the compressor runs.
I would try that first and check your pressures/temps. I bet it will drop considerably.
You may find with the condenser cooling and a small adjustment in charge (let out a small
amount) will result in better numbers.
Just a thought. Might save buying a txv.
Gary
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Bob,
All those valves are for low temp gas and pressures. They may have 410 valves......I didn't look.
As for your question about calculations Russell will have to chime in on that. He knows those numbers
much better than I do.
Gary
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Thanks, Gary. I have found zero 1 ton, R410a TXV's online so far. I suppose that's because the 1 Ton mini-splits have electronically controlled expansion valves for their variable frequency inverter driven compressor. Today, PWM control of a solenoid type valve is commonly used to create a linear valve control. An EMI cannon in EMC parlance, something I'd rather avoid.
Bob, yes, you're right for the BTU hrs calculation. BTU hrs= 8.34 lbs/gallon, X GPM flow rate X times 60 minutes per hour X degrees F water temperature change. 8.34 X 60 is the 500 you used, the proper multiplier.
Bronco's comment about my former window AC unit's condenser performance gave me a thought this morning; I'm at 5600 feet, and both the fan performance and lower air density effect on heat transfer will lower condenser performance. For combustion it's about 23%, for air flow and heat transfer, perhaps similar. I'll do some research.
Things that might improve condenser performance (shading, evap cooling) could help greatly (as Gary suggests) because of this sub par condenser performance. If designing from scratch, I'd put an upsized 1.5 ton condenser coil and fan on a 1 ton compressor.
My next step for a sunny hot day is to measure the effect on house slab and air temperature with 5 hours of run time to see if I can meet my goal of 4 degrees of heat extraction while still avoiding condensation on the PEX manifolds.
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about 15 years ago or so, i rented an apartment that was a conversion of a 3 car garage
they took out the west bay and made the apartment.
being in tacoma, it had no A/C and for a week or two in the summer it got pretty miserable when things were in the mid 90's
at the time i would spend late into the evening working on my 55 chevy with the doors open, and at night the outside temps would drop to around the upper 50's to maybe 60 deg F.
i noted how cool the garage stayed during the day all closed up, while the apartment baked.
so i would close all the drapes on the west side of the apartment, and open the kitchen door which lead out into the shop area, and set up a little box fan to draw in the cooler air.
that much cooler concrete slab would take up the heat from the apartment, and i noted rather than being 95 degree's at around 5pm each afternoon, it would only get up to about 80 degree's, which was a huge help.
we lived there for 3-4 years and each summer i cooled that place in the same manner
so i think your system is going to work fabulously!
and am looking forward to reports on how it is working out.
bob g
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https://www.esmagazine.com/articles/92538-engineering-for-high-altitude
As I expected, the condenser will suffer about 20% loss in performance at my elevation due to air density loss and fan efficiency loss.
"For example, a fan rated for 20,000 cfm will move 90,000 pounds of air per hour at standard conditions, but only 72,000 pounds per hour at 6,000 ft. Additionally, the fan laws show that a given fan operating at constant speed will draw less power and develop less pressure at altitude in direct proportion to the ratio of air densities. Fan manufacturers offer software to predict operating characteristics of their equipment at non-standard conditions."
Since they designed in a water slinging fan, that would be my first thing to test. Alas, this time of year I don't have the dry air that would really make that work well.
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the hotter the air, the more water it can hold? i think that is right
so the slinger system should work about as well as it would had the humidity been lower.
it gets humid as heck in this part of kansas, and i note that spraying the condenser sure drops the pressure and the compressor seems to appreciate the lower loads too. it makes less noise?
not very scientific, but i think there is something to it?
never considered the elevation and thinner air effect on the system, but it makes sense to me.
bob g
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Bruce,
I know the 410 txv 12k units are out there. The local ac supply house assembles them from Sporlin
parts. The day I checked I watched my friend who works there look up the parts it would take
to assemble one. He would have had to order the main body because they didn't have one that size
in stock. I was going to buy one and send it until they quoted me 180.00 plus tax. !!!!!
I will call Dometic tomorrow and see what they say. Their 12k water to air 410 heat pumps use txv valves.
Try water on the coil I think it will make a BIG difference.
I would go with the txv after you have tried the other things we have talked about. You may be happy
with what you have after a few "tweeks".
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I tried an experiment today. The pressure started at 440 on the high side, 130 low side, same as yesterday, similar conditions. I added water to the tray so the fan rim would pick it up as designed. WOW, the pressures dropped to 355 psi high side and 120 suction. It had little effect on the condenser outlet air temp, and air flow felt reduced, but it sure works, and continued to do so as long as I kept the tray filled so the fan water rim was in the water. When the water runs low, the pressure climbs again. So adding a water feed/float valve might be one solution. I did not test BTU performance, but I'm expecting it would improve as well.
I also did some investigation then with a fast acting thermometer in a hand held anemometer. The temperature on the air inlet at ground level was about 11 degrees above ambient, about 98F. I thought it might be condenser heat getting back to the inlet, so I turned off the compressor but left the fan on. No real change. I then tried chest vs ground level temperatures away from the unit but still with wind blocked by the shed. What's happening is that the ground is heated by the sun, and radiating that heat upward near the ground. It's less pronounced with more wind, but as wind slows near the ground I still see this solar radiant heating effect on air temperature. I'm also getting the same heating effect as I go closer to the west facing wall, but just being close to the ground is problem. There's no vegetation to insulate the earth.
Lots to consider; I didn't realize that radiant heat from the ground and close structures would have such a large effect on inlet air temperature. The built in water spritzing via fan rim cooling sure works, even though it was humid today from last nights rain. I wish I had a source of demineralized water; I expect my well water would turn the coils into a mineralized mess. My water is quite good for AZ but still pretty hard.
Apparently many window AC units use this fan ring/rim in water trick to get rid of the evaporator condensate, while boosting performance.
I'm not sure what my best approach is, yet.
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No......say it ain't so...............I did expect to see a change but not that much......
I do know that that compressor is much happier at 350 rather than 440.....did you get an amp
draw to see the difference ? I bet it fell off quite a bit.
One thing for sure, you won't catch rain water and use that.......you don't get any rain.......
Think you could use a filter of some sort to filter out the biggest part of the minerals ?
I use one of those big white canister filters on my home well. I change the filter every
couple of months. It does filter alot of crap out of my shallow well.
I know you will get it figured out.........
Again.....GOOD JOB !!!!!
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I see in my area many of the ac condensers are being mounted on welded aluminum frames.
They sell them at the supply house, I just never paid any attention. Don't need 'em on a boat !
Usually 18 to 20 inches off the ground. I do know in some areas they do that for fear of water rise.
Maybe there is more there than meets the eye. The units are usually on concrete slabs or parking
lots..........
Shade........if you can get enough cover for the worse part of the day.........morning and afternoon rays
are much easier on equipment than that 3 or 4 hours at "high noon)...........
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Bob,
Yes, that is the formula for sensible heat.
Bruce,
Here are links to some valves that I found that should work. TXVs for AC have an equalizer line that needs to be connected to the suction. It can either be a flare joint or it is a cap tube that will have to have a hole drilled for it, inserted, and brazed in. Or, you can get a piece of 1/4" copper flare it on one end and use a flare nut and crimp the other end around the cap tube and braze it. Valves have a range so a 1.5 ton valve should work it will just be at the minimum limits of it's flow. You can just use reducing couplings or bushings to match your connection sizes if need be.
- 1 Ton Valves:
https://surpluscityliquidators.com/products/1-ton-thermal-expansion-valve-r410a-1.html?151557
https://surpluscityliquidators.com/products/1-ton-thermal-expansion-valve-r410a.html?173449#slide_172280
- 1.5 Ton Valves:
https://surpluscityliquidators.com/products/112-ton-thermal-expansion-valve-r410a.html?171039#slide_156891
https://surpluscityliquidators.com/products/thermal-expansion-valve-8.html?155762
https://surpluscityliquidators.com/products/15-ton-thermal-expansion-valve-38-odf-odm-r410a.html?179445
https://surpluscityliquidators.com/products/15-ton-thermal-expansion-valve-r410a.html?183639
https://surpluscityliquidators.com/products/112-ton-thermal-expansion-valve-r410a-3.html?183579
https://surpluscityliquidators.com/products/112-ton-achp-txv-kit-r410a.html?200538#slide_341529
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The slinger ring is pretty much standard on window bangers these days, it helps deal with condensate and as you found they get some free evaporative cooling out of it which allows the manufacturer to use a smaller(and cheaper) condenser coil. As you suggested you need to be careful with your water source as mineral will build up pretty quickly and stop up the coil but it will also deteriorate the aluminum fins.
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Wow, thanks for the great links, Bronco. A fantastic resource for the refrigeration experimenter! They state the range of evaporator temperatures for these TXV's as going up to 50F, but my evaporator temp is 60-68F. That makes me worry about the temperature compensation bulb/valve aspect not working for my "high temp chiller" setup. It seems these TXV's might be not able to regulate via temperature outside it's design range. Is that a problem? I've also learned (I think?) that I need a bleed type TXV to avoid excessive compressor start currents as this was designed for capillary.
I noted in my reading today on cap tubes and their sizing charts that they tend to specify a 20% shorter tube length for an evaporator temperature increase of 10F, so I know the evaporator temp is important for proper flow rate.
Gary, Yes, rain water collection would be disappointing here. For a distilled water source, I might build a solar water distiller. They are pretty simple.
Regarding shading the condenser unit:
My PV panels are fixed with seasonal tilt...so my hours of operation for the chiller will be the nasty, high noon scenario.
Shade with a canvas type cover that could be put up in June after the big spring winds might work. If I used one that attached to the shop wall it would also get rid of the afternoon west wall heating/radiation.
I sure appreciate the help on this project, it's continues to be very educational, and I enjoy that.
Best Wishes,
Bruce
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Yes, thanks for the link.
I knew those parts were available. Just couldn't find them. Bookmarked that site for sure.
Bruce,
I think one of those valves would work fine. Your water temp is not your chiller plate temp.......
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You are quite welcome.
As Gary said, your evap temp isn't your fluid temp. It is your saturated suction temp. I am guessing when you get everything dialed in you will be in the 40-45 degree range. I don't think your saturated suction temp will get above 50 degrees and if it does you are going to have bigger issues.
The two 1 ton valves are the same valve except one has a bleed circuit and the other does not. I would recommend the one with a bleed circuit for your application. It allows the pressures to completely equalize on the off cycle which a rotary compressor will appreciate.
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Fantastic, Bronco, thanks for your patience and help.
I measured the temperature of the suction line about 10 inches from the evaporator/BPHE, in the 60's F. You're saying it should be 50F or below? I better retest that, well insulated.
Here's my earlier test data repeated:
High Side:415 psi cloudy to 440 sunny (122 Saturation temp)
Low Side: 128-132 psi (45 Saturation temp)
Suction temp near evaporator 68F
Liquid line temp a foot before capillary tube: 109F
Superheat: 23F
Subcool: 13F
Running amps: 5.8 (EDIT: ERROR, well over rated 4.61A, even adjusting for low voltage) with sunny at max pressure 440psi. I forgot to measure fan separately. It's less than 0.3A I need to recheck this with my RMS amp meter; my clamp on meter was showing steady low amps until I moved the wire deeper in the meter hook, and it gained an amp. So my amps checking was crap due to clamp on meter unreliability.
Water flow rate 2 GPM
Water temp in: 67.6F
Water temp out: 56.6F
Delta temperature: 11.1F
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Bruce,
I think you are looking at 2 different things........I could be wrong on this.....
You stated your low side psi was 125 (give or take) and your saturation was 45 degrees......
I don't think that is the same as your suction line temp 10" from the chiller core...
My understanding is that the guage psi/saturation temp is the temp in the middle of the coil.
You can't measure the middle of the coil in your case.
So your saturation temp IS 45.......
If I'm wrong on this let me know.
???????????
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I measured the temperature of the suction line about 10 inches from the evaporator/BPHE, in the 60's F. You're saying it should be 50F or below? I better retest that, well insulated.
You do want that line well insulated but No, you wouldn't want your suction line temp down to 50 or below at a 45 degree saturated suction temperature. Water being a much better heat transfer medium than air will tend to keep your suction line temp to within a few degrees of your fluid entering temperature.
I think your ideal pressures and temperatures once the system has been running for a little while would be a 45 degree saturated suction temperature(132 psi), and your suction line temp measured a few inches from the heat exchanger at about 55 degrees(10 degrees superheat). I would expect fluid entering temp to the HX at around 65 degrees and leaving temp at around 55. That would put your slab somewhere in the 65-70 degree range.
When you first start the system and the slab temperature is say, 72 degrees, you will see that your suction pressure, suction line temperature, discharge pressure, liquid line temperature, and fluid temperatures will be elevated above the "ideal" running conditions noted above as the chiller will be taking the maximum load it can. As the chiller displaces the heat from the slab and the slab temp starts to drop to say 69-70 you will see the operating conditions start to get closer to ideal. When the system has been running for a couple of hours and the slab is down to around 67-68 degrees you should see the "ideal" conditions noted above.
A TXV would make dialing in ideal conditions easier and would do a better job of keeping the system close to ideal during the slab pull down but isn't completely necessary. I don't think you are far off and my only real concern with your current conditions being the discharge pressure. If you can find a way to keep the discharge temperature down with shading that will reap significant gains in both efficiency and heat removal. My real concern is where is it going to be on a 100 degree day?
There is a lot more to system setup than just hitting target pressures and temperatures as all along the way you need to be thinking about component longevity, most importantly the compressor. A difference of a few psi, a few degrees, and a few 10th of an amp can make a big difference in longevity.
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Bruce,
I think you are looking at 2 different things
Correct. Saturated suction temp is derived from a pt chart for a given refrigerant at a given pressure. Suction line temperature is physically measured. The difference between the two is superheat.
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It's not trivial to have a good understanding of the interaction between refrigerant charge level. SH, SC, and the resulting water chilling performance, I'm working at it, and making some progress, but have a way to go. Thanks for the thoughtful explanations and patience with me, Bronco (and Gary).
I'll do a careful evaporator suction line temperature measurement at 3 inches and hope for something much lower than what I got 10 inches away and not well insulated.
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Bronco,
Thanks, thats what I thought. In my world I rarely have to use a chart. Gauges and my thumb will usually
get me there. Plugged dryers, plugged water lines are what I mostley see. When I have a more serious
problem then I use SH and SC and have to look them up because I can't remember.....getting old ....
Bruce,
A txv would be nice BUT you have already shown that that system has a too small of a condenser coil.
You did that with the water.....the numbers you got were just about perfect..When I see those small compressors
they normally run in the 325 to 375 or so psi range......as Bronco said for longevity it is much happier at 350 than
440........I could be wrong but I don't think a txv will solve the condenser coil problem.....water will, again you
have shown that.....
I would not waste any more time on the charge until you get the condenser worked out.
In one post you mentioned if it were you designing it you would have gone witb a 1.5 ton coil.... still too small.....
I'm thinking 2 or 2.5 to get it close in your area....AZ is 🔥 so is FL.
Look at home units. Condensers that are high efficiency are huge by old standards. More coil, more cooling.
(Yes, I know 410 is different than 22 but you get the idea)
Work on your condenser.....thats where the problem is......and well insulated lines will make a significant change.
Think cooling back to the compressor.....
Just my 2 cents.....
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Bronco, One more TXV specifications question if you can bear it, please.
Is the temperature range specification stating a maximum of 50F for the TXV referring to the saturated suction (low) side temp, not the actual line temperature? That seems an odd convention to me for a mechanical bulb sensing the physical line temperature, but every technical field has it's own conventions.
I'll mull over options for the condenser issue while I work on the control electronics and some electrical help for a friend.
If the TXV valve would stop the high side overpressure issue, that would make it worth the effort. Alas, I'm not seeing a climb in the low pressure side with the rise in ambient temperature near the condenser unit, as I do for the high side, and the low pressure side is where the TXV pressure sensor is. I continue to read and try to understand the interactions.
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I did some more testing today looking at chilling performance while adding water to the condenser, and operating in cloudy, somewhat cooler. In all cases, lowering the pressure causes a huge loss in chilling. Reducing the charge made it worse.I only got back to near the 11K BTU by increasing charge back to high pressures (430+ high side, 132 low). Again, I watched cooling slowly improve as charge and pressure increased.
The other observation is that my previous 68F at the suction line at the evaporator was correct and is only achievable after long running; it starts about 74F. The evaporator suction line temperature right near the BPHE stays within a few degrees of water input temperature, so it will never be much lower than 68F in real use.
That concerns me about using a TXV, since they are designed for a window AC unit, with around 38-45F temperature at the evaporator suction line. That's a long, long way from 68-78F.
It also concerns me about evaporator performance; I'm wondering if the ONLY way to have evaporator performance is to reduce the superheat. In this case, I'll have no choice but to run at high pressure, as I am now. I think perhaps high superheat is OK in this case, since clearly I'm extracting all the available coolth of the refrigerant, and I just need more refrigerant flow and by shortening the cap tubes I can achieve that at a lower high side pressure.
I'd love the regulation of the TXV for better performance across a range of ambient temperatures, but unless they have one for much higher temperatures at the evaporator I'm concerned.
I may try shortening the cap tubes substantially and see how that works out. From charts I've seen, a 10 degree change of evaporator temperature makes a 20% change in length. I need about 30 degrees and 60% shorter....maybe. I'll study some charts more to see how linear it might be over a larger range.
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Bronco, One more TXV specifications question if you can bear it, please.
Is the temperature range specification stating a maximum of 50F for the TXV referring to the saturated suction (low) side temp, not the actual line temperature? That seems an odd convention to me for a mechanical bulb sensing the physical line temperature, but every technical field has it's own conventions.
Yes, the specification is for saturated suction temp. And I believe that is not necessarilly a hard limit, they just can't guarantee as tight of control on the superheat outside of that range so it may work acceptably up to 55 degrees SST.
A TXV only trys to maintain the superheat setting, that's why the sensing bulb is attached to the suction line. The spring pressure inside the valve working against the pressure in the power head is designed to know what the suction pressure is and the sensing bulb senses what the suction temperature is and the valve will modulate open or closed to maintain the superheat setting that is adjusted with the stem under the brass cap. The operating/target load temperature range is set by compressor capacity and the inherrent pressure for either low/medium/high temp application. If the valve is set for 10 degrees superheat it doesn't care if it is maintaining 10 degrees superheat at -10 degrees or +45 degrees.
That is a pretty generic wide range valve. Valves can be built for specific temperature ranges depending on the application. Those wide range valves come in handy for field service or if say a manufacturer onky wants to have an inventory of a few txvs vs. one specific for each application.
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Your observations from today definitely lead me to believe it is refrigerant flow issue. You aren't getting enough liquid to flood your HX causing high superheat and high discharge pressure. Another side effect is high discharge temperature which will kill a compressor in short order, especially a rotary. Couple that with getting 13 degrees of subcooling with that small condenser and you definitely have a restriction, as in the cap tube is your limiting factor. Shortening it would definitely get you more flow.
I would ditch the cap tube at this point and go to a txv. You are fighting an undersized condenser and cap tube. It will be much easier to dial in your charge and the whole system in general with a txv. I think you could eventually get there by shortening the cap tube but it will likely take multiple attempts and if you go too short there is no putting it back. If you want to continue experimenting with the cap tube I would suggest getting a pair of service valves so you can pump the system down and isolate the cap tube and HX. Then you only need to evacuate that part of the system as you experiment. You will also need to change the drier at some point as each time you open the system up there will be some moisture and contamination that you will not be able to get out which the drier will collect and eventually clog. I change driers anytime I open a system for service. As a word of caution, if you do add service valves and want to pump the system down you will need to soak the condenser with cool water and monitor the discharge pressure. 410a builds head pressure very quickly and can be very difficult to completely pump down without exceeding the discharge pressure limits of the compressor and condenser coil.
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Also, a 60% reduction in cap tube length would most likely have you flooding liquid back, high suction, and low discharge pressures. I think you are only about 10-15% too long. You are getting enough liquid to get you to within your target SST just not enough to flood your HX and get your superheat down.
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I haven't seen the slightest change in suction side temperature at the HE regardless of pressure differential (flow). It seems completely fixed to inlet water temperature of the HE.
That makes me question the TXV regulation for my HE setup since bulb temperature is the primary control, and will be stuck at around 70F, calling for full open and never changing. I don't see how that can work very well. It's still an adjustable orifice but that's about it. I suppose the pressure feedback would do a little benefit.
In some cap tube charts I was shocked that a 10 degree increase in evap temperature results in a 20% change in same size tube length. I was looking at a chart from Tecumseh, where medium and high temperature columns used the same size tube. I have a few articles to read through still; I'm not ready to cut tubes yet.
Today I ordered a used 8000 BTU R410 compressor on ebay for $60 to use as refrigerant recovery pump. I have the terrible feeling I may be getting very good at it, if I have to sneak up on the right cap tube length.
Thanks for your help and patience!
Bruce
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I'll make some calls today to see if I can get some info.
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Bruce,
If you do decide you want service valves I think I have some of the brass ones here.
They used to be brass but a few years ago they went to steel. (Works really well in the
boat environment. Not !)
If you like I can look tomorrow and see what I have. I know I have a few new ones.
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I think your readings are off.
You said you got the best performance when your suction pressure was 125 give
or take....that means your SST is about 40......BUT you said your water temp
is 74 and the SST follows the water temp.....something doesn't add up....
Or I just don't understand .....
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Bruce,
I spoke with 3 design engineers this morning.
I will try to call you later today.
Gary
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True confession:
I got my wires crossed on the full load rated amps for my 230V LG window AC unit; it's 4.61 amps total at 230V, not 5.8! That's the amps for my well pump. I slipped a cog. So I have to re-test and see what's up exactly at that max amps. I'm pretty pissed at myself for this serious screw up.
At 4.6 amp draw, and a lower refrigerant charge to go with it, I think I'm in the sweet spot for pressures, just not getting the BTU's I should. I'll have to retest carefully, but I expect only half the cooling I need.
I realized the stock cap tube should be fine even with my BPHE as it's sized for compressor hp, so then thought to double check the figure I "knew", which is the amps for my well pump, not the window AC unit.
I hope I'll be able to incompetently bumble my way through this, but I really need a minimum of 10 degrees of water chilling at 2 GPM for it to work. That's 10,000 BTU.
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Bruce,
You making any progress ?
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Hey Gary,
I overdid on a volunteer project and have had to lay low. My health is pretty shaky.
While waiting for parts and supplies, I've been trying to get up to speed on the relationship between pressures, temperatures, and refrigerant flow rate, and efficiency. I've come a long way, though my memory problems makes it a challenge. COP or efficiency is a matter of keeping superheat close to the safe minimums. I must achieve a lower superheat and lower suction side temperature (60-65F max) in order to have the COP I need (to get 10K BTU's out of the water with 4.61A current) plus keep the compressor cool.
It's still unclear if just increasing refrigerant flow alone will result in low enough suction vapor temperature for compressor cooling, and for a low enough superheat to get a decent COP.
Swep is a company that makes brazed plate heat exchangers. They have some very helpful design articles.
This is a a good summary that relates well to my situation of too restrictive (stock) capillary tube, poor performance at rated power (my added italics):
"When a SWEP BPHE is used as an evaporator, a secondary gas or liquid is cooled as it loses heat to the refrigerant. The refrigerant boils and is converted into a gas, absorbing more energy. A SWEP evaporator provides a good, stable boiling process with a small temperature difference between the refrigerant and the secondary fluid. A low temperature difference means that a higher evaporation temperature is possible, which corresponds to a higher pressure. Reducing the pressure difference between the low-pressure side (evaporator) and the high-pressure side (condenser) will reduce the energy use in the compressor. The higher evaporation pressure will also increase the density of the refrigerant gas. For each stroke, the compressor will therefore transport more refrigerant through the system. Lower electricity consumption and higher refrigeration capacity will increase the total system efficiency (COP). "
They also have a good article on capillary and TXV valves. Alas, they don't specifically address my water temperature being so high. Another problem with high water temperatures is that the suction side vapor temperature is above the normal 60-65F maximum temperature for cooling the compressor. The return vapor is run inside the housing for pump cooling, and is the primary means of pump cooling.
I did think of a plumbing cheat that might be useful; by adding a bypass valve on the water to and from the BPHE/evaporator, this would allow the BPHE water (and suction side) temperature to be lower, while keeping the temperature going to house above 58F (to avoid manifold condensation and mold). This might allow the use of a standard TXV and operate at lower (high side) pressure. The normal TXV line pressure and temperature balance will be outside the normal design range otherwise. This also gets suction temperature below the 60-65F that is specified to provide compressor cooling. Right now, if water temp is 78F, so is the suction side, and that's BAD news for the pump temperature and life. This could also be helpful for a capillary tube expansion valve, in that it allows for the return vapor temperature to be within specs for compressor cooling. One issue with this water bypass method is that water flow may have to be changed to the same direction of flow as the refrigerant to lower suction vapor temperature. Right now, suction temp tracks inlet water temp...too high!
I found that there are no manual/hand expansion valves rated for R410a pressures. They were used and are still being made for R22 level pressures.
I did find a teflon packing, high pressure needle valve that could be used in addition to an intentionally short cap tube to make up an R410a rated manual adjustable expansion valve. Most high pressure needle valves use viton o-rings/seals and refrigerants eat Viton. EPDM is fine, but they don't seem to use that.
Today's project is to build my reclamation pump with the used R410a compressor and filter/dryer. I'll still use ice water in a bucket around the reclamation tank.
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Bruce,
I personally would not play with the "manual valve". I don't think you would ever be able to get it right.
The tolerances are just too small plus you don't have a known starting point. Would be easy to flood the
compressor with excess refrigerant.
Also RLA is usually the maximum. Most units will run well under that number. With that 4.6 number I
would be looking at around 4 amps more or less. As an example I am running a small water circulation
pump on my Ashwamegh. Today I got it running and with a load and 3' of head it is drawing .27 amps.
RLA is listed at .35......Most of those small compressors I'm around run under. When they get close to
listed RLA I am looking to see if there are other problems.
As usual take I what I say with a grain of salt !
Gary
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Put together the recovery pump and fittings. capacitor, switch and cord. Simple enough, runs, not bad for $60.
I decided to test the recovery pump. It worked nicely, only a few minutes to pull out 1.5 lbs of refrigerant into a tank in a bucket of ice, and pull a soft vacuum. I then put in a couple psi of nitrogen so when I cut the lines it wouldn't be sucking in air.
I ordered the Emerson 1 Ton R410a TXV with bleed that Bronco found for me at SurplusCityLiquidators.com. If I can get the suction temp down to where it will operate, it could help improve performance in a wider range of ambient temperatures. It's well worth trying. The equalize line is a PITA, but can't be helped.
For education, I want to try a shortened cap tube first. On JB Industries cap tube reference chart, page 4, is the dual tube, R410a, 1.5 HP unit like mine. They show dual 34 inch. 0.049 ID tubes. I"ll check the OD and length of mine when I cut it out tonight to check that it matches. That's for AC use with a temperature of 45 degrees. The next colder entry is 25F (refrigerator), and is 44 inches. So about 10 inches for 25 degrees colder. Going warmer SST by 20 degrees (65F when incoming water is 75F) should be 8 inches shorter if it stays fairly linear. So I might shorten it 6 inches and see how it performs as I sneak up on the proper charge.
The sun and reflected heat problem in the afternoon at the present location is BAD news, and the low volume fan is a problem for mixing output and input air when the wind is from the north, which isn't uncommon in the summer.
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My dual capillary tube was originally 63.5 inches. Close to 0.046" ID. It's now 62 inches.
Alas, 60 inches is the minimum distance for linear response to length and less than that, it acts more like an orifice, so small changes can make a bigger difference in flow. The JBind.com R410 dual tube data shows:
3/4 hp line (106 to 70" 34% shorter, for 25F to 45F entries
1 hp line goes from 83" to 42" - 50% (!) shorter, from 25 to 45F respectively. This DOES NOT FIT!
1.5 hp line (44" to 34"- very short and thus quite non linear) only changes 25%.
A variation between 25% and 50% shorter for 25F warmer is not very helpful. I see the same range of variation in other refrigerants and in single tube charts, when looking for entries around 62 inches, going shorter.
Not helpful. Every little detail is an educational project.
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https://icemeister.net/backroom/wp-content/uploads/2015/04/AndySchoen_A-Modern-Method-of-Properly-Sizing-Capillary-Tubes.pdf
Tecumseh has some data here on non-R410a refrigerants, showing a consistent 28-29% shortening of tubes in the 60 to 72 inch length range going from 25 to 45F evaporator temp. Less for shorter, more for longer. So at least consistent with the theory of optimum length 5 to 10 feet and with reason, unlike some of the JBind data.
I'd like to see a 15 degree reduction instead of 20F in evaporator suction side temperature (SST), so will shoot for 21% reduction, but because of my shorter length, perhaps 18%. So 11 inches shorter.
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Cap tube shortened by 11 inches, reinstalled, pressure test and purge with nitrogen. Now pulling a vacuum for a few hours before recharging. I'm getting a bit better at standard procedures.
One finding of note: The BPHE has become an oil reservoir, exactly as Bronco suggested, with flow from the bottom. When I removed that fitting, oil was dripping out. I quickly capped it, but I should probably add POE oil to compensate, or perhaps reorient the BPHE for the less efficient, less reliable refrigerant entry at the top with lines sloped downward to the compressor.
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Baffling findings.
Limiting charge to 4.6 amps, I get only 1.3KBTU of cooling.
High pressure:290 psi
Suction: 47 psi
Water in: 75F
Water out: 73.7F
Suction temperature: 75F, so a rediculously high superheat, and thus pathetic BTUs.
This lowering of suction pressure is the opposite of what was supposed to happen according to my reference.
https://lando-chillers.com/the-effect-of-capillary-tube-length-on-the-performance-of-refrigeration-system/
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I don't know what's going on but do know the suction pressure is way too low.
Are the cap tubes freezing as before ?
Are you sure your amp meter is correct ?
If you add more gas does the amp reading rise excessively ?
???????
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Cap tube into BPHE is cold with some condensation but not frosting.
Yes, increased charge raises amps above the 4.6 rated max, I took out some charge to get back down to 4.6, and I'm using my best clamp on amp meter. Checked it against a RMS 120V power meter to be sure it was fairly accurate.
But the real baffler is why didn't suction side pressure come up. Suction temp near BPHE is still exactly the water inlet. Suction pressure is WAY low, as if starved for charge, but no frost, and amps show full charge, increasing with an increase in charge.
Hopefully I'll see my next step when I feel better.
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Every thing would indicate a low charge except amp draw.
The cap tubes should not be cold except at the plate.
Low head pressure.....low suction pressure......
I'm baffled.
I would gently add gas and see where the amp draw goes.......does the compressor have its own data
plate ? ...........
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I like to your theory, Gary. It fits. I suspected it myself until I saw the current being 4.8 amps. I thought that I didn't put in nearly enough R410A; I found my bathroom scale was not seeming to read correctly, then caught it changing values significantly on subsequent re-weighs. But still, the faceplate calls for 20 oz, and I did not put in that, or the 4 oz for the dryer, and 2 oz for the extended copper lines. (I'm ordering a postal scale.)
What I'll do tomorrow is some new wiring to allow for inline RMS current sensing in addition to my clamp meter and then keep adding in some refrigerant and see what happens. I won't stop until the current goes substantially high (5.6A) and stays there. Today I stopped immediately and backed off when it got to 4.8 amps... perhaps I should have just waited longer??? As I let some high side liquid back into the recovery tank, the current did come down, slowly.
I'll retest and see what happens with more refrigerant, and I won't stop until it gets well over 5 amps, and will let it run and see if it goes down after a bit.
Thanks for your good thoughts!
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Good news; The problem was both meter and apparently a blip of higher current during filling, plus not realizing that my inverter 230V was more like 217 a the unit due to my use of an extension cord for a temporary hookup.
So, my hat's off to Gary; he diagnosed it correctly as undercharge with bogus high amps.
Alas, the suction side temperature has not come up enough, yet. But BTU performance is somewhat improved at normal max power; 8.5K BTU to the water at 4.8A/217V. As the outside temps got warmer from the sun heating the west wall of the shop and thus the air around the condenser unit, I lost 1K BTU. As the math turns out, BTU's are easy with my setup at 2 GPM; every degree of cooling is 1K BTU. (8.5 degrees = 8.5K BTU)
The ambient air into the condenser fan was 95F, and the high side temp was 115F. Room for improvement there.
High Pressure: 390-400, low side 115 to 120. High side temperature 115F. Sub cool near zero.
Suction temperature at BPHE: 70F Superheat= 29, the horn in my efficiency side.
Since low side pressure and temperature have not come up, I'm reluctant to shorten further. I think my next move is to add the water bypass valve, to allow water temp in the BPHE to drop lower, thus lowering my suction side temperature, superheat and hopefully improving my BTUs.
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Looks like you are getting close.
400 psi head is not bad but if you could shorten the tubes a little more and run the
head near 350 to 375 I think it would make a big difference on compressor life.....
Did you run water on the condenser? We know that will lower the head.
Tell me about your bypass idea. Yes, lowering the water temp will help lower pressures and temps.
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I found some old test notes:
With the stock cap tube, 5.0amps (at 218V) 350/110 PSI, 95F high side temp, evap suction temp 69F. Must have been cooler.
Still, only 5K BTUs, despite the slightly higher BTUs.
5K BTU is 1465 watts, with 1090 corrected watts input, is a very poor COP of 1.3 .
With the shorter cap tube, 4.8 amps at 218V, 8000 BTUs (at higher temperature), 2344 watts of cooling over 1046 watts of power is better but still poor COP of 2.2 .
So I'm making some improvement.
The high side pressure now tracks my condenser liquid temperature, which tracks the sun baked, 10F over ambient air at ground level in the sun plus 15 degrees. The bugger is the low side pressure isn't coming up as much as I'd like, since it's pegged at the incoming water temperature.
Perhaps I should consider another shortening for educational purposes.
The water bypass method is to plumb in a bypass for the BPHE, so that only some of the water goes through it. This would allow the suction side temperature to lower even if it's still tied to water temperature. I'm not sure if this is a viable means of improving COP/BTU's, but it could get the temperature of the EXV bulb to within it's design range. It may not be necessory if shortening does the trick.
I'm interested in the concept; it's similar the method used industrially to keep up efficiency, when cooling a large tank starting at a high temperature and going all the way to a cold one.
A BPHE with fewer plates also comes to mind.
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i am placing my be on the deletion of the cap tube and the installation of the expansion valve.
i like things that i can adjust to tailor things to get the result i want.
cap tubes to me seem about the same as having to adjust an engines valves by having to grind the end off a pushrod, not enough and the engine loses power, too much and it clatters.
poor analogy? i know... hey its late and i am getting old!
bob g
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I found some research papers to study, about superheat, subcooling and COP. I skimmed some of it and it seems I'm off the mark entirely on reducing superheat to get a better COP. An academia mind bender, no doubt.
I'll do some tests tomorrow morning when the air temps are cooler and see how that performs. That will improve my pathetic subcooling and increase COP and BTUs. I'll try some water as well.
I agree with you on having adjustment, Bob. It's just that I need very hot days to get valid data and so I'm trying to learn all I can before the TXV gets here. Thus the jury rigged power, etc. Today I had to take time to repair my old Eaton air compressor pump which the Lister CS drives. The output valve was leaking, and the downstream check valve failed, also. Luckily I had a spare check valve on hand, and was able to clean up the compressor disk valve after welding up a special spanner. Things never fail until you're rushing on another project...
Lucky for me, damned hot this week and sunny.
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Bruce
i understand the wanting to learn all you can about the system while you are waiting, very well.
don't think for a minute i am trying to teach you anything, you already know more than i do on this subject, that is why i am following with interest.
sometimes i just can't help myself and i have to chime in with unsolicited input.
one way or another i am confident you will get this worked out, and we will all learn from your efforts... that is what makes for a good forum.
having to learn everything on ones own got really old, sure nice to have a place where one can draw on other experiences or live vicariously as i do. :)
bob g
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Got some 80F (condenser fan input) data this morning on Lister power.
High side- 340 psi, temp 95.9F Low side- 102 psi, temp 72F
Water in/out 72.4F, 63F
230V x 4.3A (rms)= 989 watts
BTU is 9360. (2734W) Below my minimum cooling required, but getting close, and there's some head room on amps.
COP = 2.76. Better than a hot afternoon at 2.2 but still not good.
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I'm curious about your temp readings....
Hi side 340 (I like that ).....temp 95F...where are you reading that ?
Low side 102 F (might be just a tiny bit under charged) @72 F....where are you reading this ?
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Hey Gary, My high side temp is measured just before the cap tube indoors, the suction side a few inches from the BPHE. Both are insulated for their 6.5 foot length.
My high side was the standard 15F over air inlet, which is often 10F over ambient on a sunny afternoon from ground heating. The sun is intense at 5600 ft.
I tried several experiments this afternoon. One was putting up a tarp awning for shade. That did very little, since the ground was already warmed up. It dropped current slightly. No measurable change in BTUs. When I add water to the rimmed condenser fan bath, current drops 0.4 amps and BTUs increase just slightly. Not surprising as the same performance gains are in the morning at cooler temperatures. But it is not huge.
I next tried changing the water flow direction through the BPHE. This made no difference in water cooling, but it lowered the suction side temperature to match the cooler outgoing water temperature, today about 64F. This is better for cooling the compressor so I'm leaving this change for now. It made no change in BTUs, still 9000. This lack of improvement with reduced Superheat agrees with an academic research paper using a computer model that suggests that lower superheat is not helpful for improving COP.
Next I decided to blow my last nitrogen before my neighbor gets me a refill on Friday. I shortened the cap tube 10 inches this time, just to see if again I get some improvement on BTUs and COP. A quick braze, installation, then pressure test on nitrogen, followed by nitrogen purge till my little tank gave it's all and it's back in now and I"m pulling a vacuum. Having flare fittings on both ends of the cap tube is nice.
I don't see why I shouldn't be able to get a COP of 3 like all the other guys do. Fingers crossed for tomorrow.
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Results are great on the total of 21 inch shortened cap tube (stock 63 inches, dual tube).
My BTU's have gone from 9000 to 13000 at 4.5 amps/1035W total (fan plus compressor). Water in: 69.8 after running for a while, water out 56.8F. My COP has gone from 2.76 to 3.68 ! (3809W/1035W)
What a difference the proper expansion valve flow makes!
My suction side temperature is 54.5F, still closely tied to the water out (I'm using the "wrong" water flow to make it lower.)
This is good because most compressors specify 60F for the minimum suction temperature for compressor cooling. The vapor enters the hollow pump cavity to provide essential cooling.
Ambient Conditions: 80F, morning shade. Measured at fan inlet, also 80F, Fan outlet 94F.
Amps: 4.5A I stopped here as incrementally charging as spec is 4.6 at 230V. I can operate at a lower charge and amps, to allow head room for hot afternoons if not using a TXV.
High pressure: 356 psi, Low 127 psi. (low gauge reads 10 psi low at 200 psi equalized)
Temps near BPHE: liquid line 94F , suction 54.5F (water out 56.8, wrong flow direction used to lower suction temp).
I expect the amps to climb with heat, and I'll check that this afternoon. That would be where the TXV would help, as the increased liquid line pressure will throttle back flow, reducing amps. Even though the superheat bulb won't do much. The unknown is if this Emerson TXV will allow the much higher flow rate I need with air to water cooling, instead of air to air, as it was designed for. A 1.5 ton unit might be needed, if so. First I'll see how much the temperatures affect current draw this afternoon.
I'm relieved that I'm finally getting the BTU's I need, and a decent COP for an 80F morning.
Edit- Addendum of follow on testing with increased outdoor temperature.
While still in shade, and condenser fan inlet now up to 90F, (10F increase), and current climbed 0.4 amps. I reduced the charge until 4.5Amps again, noted the low side pressure just below 100 (indication of too little charge) and got only 8,000 BTU of cooling. So now I see the need for a custom tailored TXV to get an optimal COP, you really need to adjust the expansion valve flow rate to control amps, not starve it for refrigerant charge. This means I'm now too short on the cap tube for inlet air temps over 85F.
Next week I'll try to make it work with the surplus Emerson TXV. Hopefully the Emerson unit will be sufficient; pressures rise with temperature and motor draw, and that should decrease TXV valve flow. Otherwise, I'll have to go with electronic controlled valves. Some are quite cheap, but I've not designed or seriously researched stepper motor drives before. I could control the expansion valve based on motor amp draw and outgoing water temperature. The latter to intentionally limit the low water temperature to avoid condensation at the PEX manifolds.
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Or.......not enough condenser.......
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From what I've read, refrigerant liquid temperature roughly 15F above ambient is normal for a condenser. That's what I'm getting when I check the temperature at the back of the fan compared to the high side liquid temperature, though in some conditions my inlet air temp gets 10F above ambient. I did look for surplus condenser coils but came up empty. I do have the original air evaporator which I could add in parallel. But that might only buy 5F. I'm not sure it's worth it.
I wish I'd started with a bit more excess BTUs; it's easier to lose them than gain them.
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not something you probably would want to do at this point, but...
maybe another water cooled plate exchanger for the condenser? you could heat your hot water? for domestic hot water needs?
it would be interesting to use the heat taken from the slab and put it to use preheating water.
ok, i will retreat to my corner
:)
bob g
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No retreat warranted. Alas, I have no need for lukewarm water in the summer. My 800 gallon insulated solar hot water storage tank is maxed out.
There's a reason the HVAC industry just uses air; cost and simplicity, power be damned.
Speaking of damn the power:
I keep waiting on the battery tech to improve. If I could run my little 1060 watt slab cooling system late at night and early morning that would be a big help. But LiFePO4 is still bleeding edge and has some reliability/durability issues to be worked out. Not to mention I'd have to design and build 39 battery regulators and a new BMS for it...and work through the birthing issues of that new hardware design. People forget that a simple failure of the BMS can wipe out a cell or an entire bank. All it takes is a lightning spike on the power or grounding system.
I'm getting close, just don't know if I'll be able to test the full range of temperatures as I won't get the TXV and fittings until mid week. I suppose I can restrict the condenser air flow to get the desired "simulated hot day" test liquid line temperature. I think that might work.
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....... People forget that a simple failure of the BMS can wipe out a cell or an entire bank. All it takes is a lightning spike on the power or grounding system.........
Some BMS's are so poorly engineered ( if at all ), that they are going to fail, and take out the battery bank with them.
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Looking at your numbers again I don't think you are that far off.......but
At 80F your numbers look good as far as pressures and temps but the compressor amps
still look hi to me. We usually look for RLA to be 10% or better under that number. I can't
stress this enough. You will loose some cooling but you said you were getting 13k out of it....
It's a 12k unit......I would look for 11k or so. ....I have always tried to be conservative on the numbers.
Reason being the rise in amps and pressures when the outside air temp goes up.
Your idea of using the evap coil on the condenser side might help. Lowering the condenser coil temp a few degrees will make a significant change in head pressure thus amp draw. Look at all the newer home ac
units. The coils are huge compared to older units. (Yes I know different gas types, etc..) What I see is that
the higher the s.e.e.r is the larger the coil. Some of the super hi efficiency units have 2 layers of coil in the condenser. There must be something there.
The TXV sounds like the answer.....but be aware that it could be opening a can of worms so to speak.
You could end up going in circles and be no more ahead than you are now.
As always, take this with a grain of salt..........
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LG is running the compressor 6% under max rated power at their appliance (compressor plus 80W fan) power rating of 4.6 amps/230v. At 4.5A I was running it 8% under rating. I'm still at the education and experimental stage, Gary. I'm nowhere near a setup for operating at full range of temperatures. I wouldn't mind running close to full watts on the compressor for a 103F ambient, if vapor temps were at 60F or less, because I only expect less than 40 hours of run time a year. That's 800 hours in 20 years, well beyond my likely expiration.
Floor cooling is a slow process since you CAN'T throw power, very cold water and BTU's at it. If the house was 80F (return water 77F) and 60% humidity from being closed up for smoke, you don't want the water below 67F at starting conditions. So about 10 degrees of cooling is all you can use or you get condensation build up at the pex manifolds in the wall cavities. As the room temperature goes down, so does the dewpoint, so near 10K BTU is OK, but it is the maximum...assuming house humidity is 60% or less. [Note to self- put manifolds where you can deal with condensation if you're planning for cooling!] Again, I'm going to have to do some experimenting to work it all out, but my concept was to keep BTU's near 10K, and not much over, unless I increase the water flow rate, which is also a relatively simple option, and I have the extra 12V circ pump on hand. If I can't get 4 degrees out of the house with 5 hours of running, I'll increase water flow to raise water temperature and raise the BTUs.
Sadly I need that 9 or 10K BTUs in the high noon and afternoon to use my excess PV power.
I may do a wee hours of the morning run on Lister CS power just to see how manifold temperature and floor temperature changes over 4 hours of running, with refrigerant charge adjusted for 9-10K BTUs. I want to see how 10K BTU's performs on house temperatures over the following hours. My house is a slow moving temperature mass.
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Shoot Bruce, you know I don't know anything !
I think you are doing a fine job and am confident you will get it going.
Probably do better if I leave you alone :laugh:
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Bruce
just for my own amusement
how do you have the water flow going through the exchanger?
is it inline or counter flow?
something popped into my noggin last night, (frequently happens about 2am), that is the heat flow in an exchanger often times improves with counter flow.
just curious
thanks
bob g
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Hey Bob,
I started with counter flow, but am now running inline, in order to have lower suction side vapor temperatures, which are needed for compressor cooling. It dd not measurably change water cooling. My 40 plate BHPE is a bit larger than I needed.
I've been doing some reading on the influence of higher temperatures on air cooling performance. I didn't realize how huge the COP/EER losses were as outside temperature climbs.
From this paper with some R410a testing data, page 6:
file:///C:/Users/Bruce/Downloads/A_Comparison_Of_An_R22_And_An_R410A_Air_Conditione.pdf
"If we evaluate the combined data obtained with both compressors, the air-side capacity decreased in a nearly linear manner as the outdoor temperature increased from 27.7 °C (82.0 °F) to 68.3 °C (155.0 °F). Over this temperature
range, air-side capacity decreased from 11.8 kW (40345 Btu/h) to 6.7 kW (22699 Btu/h); a decrease of 43.7 %. The COP (EER) also decreased linearly by 80.3 % as it dropped from 5.36(18.3 Btu/Wh) to 1.06 (3.6 Btu/Wh). "
This performance affect of ambient temperature is much, much higher than I expected. With the ground heating effect, my air inlet is 10F over ambient. My worst case ambient is 103F. So a condenser inlet of 113F. That will give me a COP reduction of 33%, (in my case from 3.5 to 2.35). This has a huge effect on my BTUs, since I don't have enough head room at the compressor for increasing watts much. I should have started with a larger compressor, and limited it's BTU's and watts at the evaporator valve. Then power could climb as temperatures rise to keep the output closer to 10K BTUs.
Evap cooling will buy me 20F in June with single digit humidity in the mid day, so I'd be OK at 103F ambient. I don't like it because of the maintenance with my hard water, but it would be a huge energy leveler/reducer that could make my current condenser unit viable. One thought that comes to mind is since my run hours per June and July are low, if I could find a descale chemical spray to use that wouldn't wreck the fine aluminum fins, maybe I could just use the fan rim system with my well water. That's super simple; I just add a tray and float valve, fed by 1/4 drip tube, controlled by a solenoid triggered by ambient air temperature. I'd just have to blow out the water line in the fall.
I'll probably have to add a water bypass at the BPHE, also, to allow the TXV suction line bulb to in effect, limit the outgoing water temperature. This lets the water (and suction vapor) temperature in the BPHE to be lower than the re-combined combined water temperature, by diverting some water directly from inlet to outlet pipes, not going through the BPHE. I tried to get the 1" Pex crimp tees I needed for this yesterday but ACE didn't have them.
I've read some papers about R290 performing well for higher temperatures, and will follow up on that reading to try and look at their data to see if it's significantly better. It requires a larger volume capacity compressor compared to R410a; R22 compressors are a better match.
More research required, while I wait on the TXV.
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Bruce
all i can say is wow, what a job you have done with this project, i for one have learned a lot from your efforts.
another thing comes to mind when you mention the heat soaking of the ground around your unit being ~10deg higher than the ambient air. i can get my head around that as my temperatures are quite high on the ground as the compressor/condenser unit is on the south side of my house and the house is a light tan color, a lot of reflected heat down onto the ground.
what i am thinking of doing is building a cooling tower out of cedar siding planks, a simple affair maybe 4 ft square and maybe 6-8ft tall, with a drip water system as you describe to trickle down the cedar siding slats.
how effective that might be at lowering the temperature that the A/C unit has to operate in, because of my location in east central kansas and higher humidity levels i am not sure. however i think it would still drop the air temperatures substantially given the elevated air temperatures.
i also have a well so i don't have to use city water, however the limestone strata that all the well water around here comes through has a high mineral content... so like you i don't want to spray that water on the aluminum fins either. and i am sure that after a summer of dribbling down over the cedar slats of a cooling tower they would have a good start at being petrified. Not that it would affect the function, the look would be less attractive, but who cares its in the back of the house and no one but me would see it.
i don't know whether something like this would be of use in your application? maybe?
perhaps some of the professional cooling guys can chime in with their thoughts
bob g
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Most articles I find are for larger systems, but the acknowledge the mineral problem with direct water misting on the condenser. They instead opt for indirect water cooling, so that only vapor enters the condenser. Your scheme is indirect. If you had misters located in the condenser area but avoid any water droplets getting directly to the condenser fins, that would do it.
I've had swamp coolers with pan, pump and aspen pads; they work reliably since there are no misters to clog. Not easy to fabricate from scratch. I'd like just one panel from a good sized unit!
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I tried just spraying water on the ground to see if that would help with the ground heat effect. No, it didn't make any change at the condenser unit air inlets. So it seems a true evap cooler design is needed.
Oh, how I wish I'd started with a 15000BTU, 1500W 230V unit.
I'll probably proceed with adding my leftover evaporator to the condenser, adding an evaporative precooler using the greenhouse type cooler panels, and adding an insulated chimney with a hat on the air inlet to get it up above the ground heat effect. It's all simple mechanical stuff. I may raise it up to improve serviceability for the precooler.
I found an article on BuiditSolar that some might find interesting.
https://www.builditsolar.com/Projects/Cooling/ACEvapCool/ac%20pRECOOLING%20G1-1.pdf
His A/C wasn't cooling enough on very hot days, so he added a precooler. Since he used the greenhouse panels I expect not much water makes it to the coils. I'll separate mine further. He got very good results.
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Bruce
thanks for the link!
yes i agree he got some very encouraging results!
bob g
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Remember that low humidity is key to good results with evaporative cooling. When humidity rises to 33% (as in the predawn June hours here), your're lucky to get 8F of cooling. June days here are single digit humidity, so 20F of cooling is common. I experimented with a water chilling tower, and with evaporative/night sky cooling trickling water down roof panels at night before undertaking this more conventional water chilling via refrigeration project. My pre-dawn, prime cooling hours had too much humidity and any clouds (or wildfire smoke) wreck the night sky cooling effect.
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I've been looking for a condenser fin/tube unit to add to my setup, to reduce my condenser approach from 15F to half that. I've got to do a whole new housing for evaporative cooling so I might as well upgrade the condenser. New aftermarket automotive condensers are affordable and readily available but I wonder about running them in a R410a system since they weren't designed for the higher pressures. Any thoughts? Also, for plumbing, any suggestions on series versus parallel?
I'll be running a 10K BTU test for about 4 hours tomorrow morning, 6:30 to 10:30 on Lister power. I opened up all afternoon to warm up the house a few degrees and the slab will have all night to soak in that heat and stabilize at something like my actual June use conditions. FIngers crossed; my delta T is low (10F) and so is my flow rate of 2 GPM.
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I think all the car condensers are aluminum.......and they run much lower pressures.
I would series the additional coil. If you put one behind the other, with the existing fan I
would pipe to the aft coil first then to the one next to the fan. In the top out the bottom, then
again in the top out the bottom.
I think I read, or perhaps you told me, your access valve was directly off the compressor. Your
access valve should be after the condenser. I have read that there is a 10 to 15 psi difference
between those two spots.
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I'll have to check for copper condensers, thanks for that, Gary.
My high side service valve is pre -condenser; it's where they had it originally. I can't imagine much of a pressure drop more than a few pounds given the relatively modest flow rate of a 1 ton compressor and the two parallel 1/4 tubing paths in the condenser, but I'll look into it.
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I've got test cooling data from 5 hours of running this morning, starting at 78F for air temperature, 77F for floor.
Bottom line: Slab temperature down 5F, about the 1F per hour, as I was expecting. Slab a foot from the manifold down 10F. Air temp was only down 2.4F, but I expect that to continue to drop for the next hours.
No sweating at the manifold, BTUs averaging 10,860.
BTU's started at 12K, ending at 9.9K,
Current started at 3.9A and ended at 4.5A, 230V.
COP started at 3.9, ended at 2.8. (65F to 83F)
Outdoor air temp start at 65F, ending at 83F, fan inlet started 65, ended 85F. Liquid line temperature ended at 105F, a 20F approach, which is very bad, the condenser and/or fan needs work. This is the first time I've done a run with the case on, which seems to be restricting airflow. Fans and fins work about 23% less at 5600 feet.
My minimalist floor cooling approach is working somewhat but I have to wait a few more hours to see if I need more BTUs.
I forgot to add 1.5 degrees to the digital temperature on my wall to calibrate it with the other analog thermometers, and got over excited about performance. It's come down only slightly since I stopped the active cooling.
Edit:
Allowing for the 3 degrees F of gain I would normally get on a breezy 88F day, I did get about 4.5 degrees of benefit from 5 hours of cooling. So just barely meeting my needs.
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I evacuated the system and put in the Emerson TXV today. When pressure testing on nitrogen I had a surprise. The cap that closes off the adjustment (6 mm hex key required) seals off the high pressure line as well. I left it loose expecting to adjust it...it leaked badly until I tightened it. So you cant's adjust the thing unless you are willing to evacuate the system. Not very helpful for my setup as there is no way to easily "dial in" the best performance.
I don't know if this is common or if it's why this Emerson model was so cheap and readily available.
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i don't remember any of the expansion valves leaking while adjusting them?
that seems odd
bob g
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I'm with Bob on this one.
Look carefully near the adjusting stem and see if it has a packing adjusrment.
I doubt it but it's worth a look.
It's been a while since I've looked at one.
Gary
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No packing, the adjustment is deep inside the open cavity via 6mm allen key. Adjustable means they can figure out the turns for different models the hard way; not ideal for an experimenter.
I wasn't expecting this kind of "adjustable".
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I think you got a bad valve.
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The Emerson ANCEB-1-ZW-195 is apparently designed this way. Not perfectly clear from their website but for the A series valves, the second letter, N, means non-adjustable. It's in their economy series. Thus the adjustment that isn't adjustable with the system charged.
Who knew such a thing existed? Not me!
Now I've got to search again for an actually adjustable TXV with bleed, 1 ton, R410a.
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That is a bad design. Never seen that before.
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I'm having no luck finding an appropriate valve. Lots of the 1.5 Ton, but not for R410A, 1 Ton. I expect since all the smaller units have gone to inverter/electronically controlled expansion valve. I'm visually exhausted, will try more poking about later.
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I wouldn't be afraid of the 1.5 valve.
Many of the units in the 12k to 16k btu range use the same txv.
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I can get the proper sized valve, with specs for suction temp of 58F, from China- in about a month. They even have SAE flare connections available, which is nice if you need to replace the valve.
I'll look at the 1.5 ton units carefully.
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Check the Sporlin website.
Build one. Look thru the txv charts and I bet you can figure it out.
My local counter man looked it up and had the parts list in about a min. Granted, he has
put a few of them together, but it's not an everyday thing. It's just a few parts that get screwed
together.
Call a local ac supply house and see who builds them in your area. Most supply houses
know of each other and what they do. You may find someone locally that knows the numbers
right off
Or at least someone who can point you in the right direction.
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Sporlan is the highest priced TXV maker in the world, as far as I can tell. Too rich for my low budget experiment with higher suction temperature, BPHE water cooler, I think.
With a bigger budget I could nail down this floor cooling thing quite nicely; a bigger condenser coil with much better approach temp, slightly bigger compressor, increase the in floor water flow rate to 4 GPM via Lang D5 Strong pump to allow higher indoor humidity and add an evaporative pre-cooler plus air intake about 6 foot above ground level to reduce air inlet temps another 10F in the afternoon sun.
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I can't argue with that.
Reminds me of when I was quite a bit younger I had an older friend who would say:
"Only one thing cash won't cure !"
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Ha! Bad headache today but maybe tomorrow I'll evacuate then charge and give the Emmerson a go.
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I took out the TXV that can't be adjusted without evacuating the system, and put in a needle valve plus the cap tube.
That let me restrict flow as temperatures climb to keep a constant 4.6 amps.
I tried wood then a metal cover for the condenser coil to restrict airflow so I could simulate a hotter day. The leaky stack of lumber gave better results; the metal cover seemed to cause greatly elevated current for the same temperature. Something about too much of the coil not being cooled at all. The metal cover is shown in the picture.
As liquid line temperature got above about 95F, the BTU perfomance starts to fall off rapidly. I'm able to get 13.6K BTU's at 90F, 13.0K at 94F, 10K BTUs at 102F. Then it falls on it's face, and there's no chance of it not being adjusted properly, since I was doing it manually while watching compressor current, every so slowly.
So evaporative precooling is a must; my former LG window unit doesn't have the advertised 12000 BTUs, EER of 11.3 at 95F ambient at my elevation, at least. (95F would be 110F liquid line temp at 15F approach). I'm not getting anywhere near this performance at 95F equivalent liquid line temps. More like 4000 BTUs.
I can likely live with the needle valve/cap tube combo, but could get the best cooling performance with an electronic expansion valve and custom microcontroller programmed to adjust for max rated amps. They are cheap, but no one but me could maintain it or appreciate it.
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This afternoon I picked up the bargain bigger brother of my 12K BTU LG; the 18K BTU model from a nearby seller on Craigslist.
It has a bum evaporator side blower wheel, that is making some slight noise, and was pretty dirty, thus the new bargain price of $150. I'd been watching it for a few weeks.
I ran it before taking it apart for a good cleaning and inspection; it draws 1600 watts while running the blower on high. The compressor sounds good and the air was cool. The total unit and the condenser seem huge compared to my 12K unit. The fan motor on the 18K unit is 276W instead of only 80W for the 12K unit. One option is to use the 12K compressor on this chassis, with it's much larger fan and condenser coil. The fan will have extra power for the evap cooling without a supplemental fan.
The question in my mind is if I reduce the power via cap tube/needle valve combo, can I still get good BTU levels. Even more interesting would be if I can get acceptable performance at higher temperatures without adding an evaporative pre-cooler.
I was surprised that this unit has an LG compressor, made in Korea.
I just couldn't resist it for $150.
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An update:
I built an insulated tower for air intake at 6 foot for cooler air (10F hotter than ambient here near the groundin still air from sun heating of the earth), and an evaporative pre-cooler. The precooler is just a single aspen pad, with a standard 230VAC evap cooler pump (70W). I upgraded to a new (surplus on ebay) Panasonic 1350W compressor after finding that the used LG compressor had starting problems, and lousy performance at higher current draw.
I added an Arduino nano, power monitor via I2C, 6 Dallas one wire temperature sensors, and a 4x20 character LCD display, and a stepper motor driver board for a Chinese EEV. I also got a larger brazed plate heat exchanger, and increased my water flow rate from 2 GPM to 3.2GPM with a Lang D5 12V pump.
It now cranks out 15-17K BTU (10 degrees of cooling at 3.2GPM) on 1400W to total power (320 of those watts for fan and water pump), the compressor is loafing and runs at only 115F on the top of its case.
The one area that needs work still is that even going to a larger EEV I have found that my filter dryer seems to be restricting flow enough that there is no change from opening beyond half way. That's an easy fix problem but today I just wanted to take advantage of the heat and give it a long shake down run.
As I write I am now (ever so slowly) cooling my house while its about 95F outside, on my solar PV/inverter system. Its been a very educational project.
Evaporative pre-cooling makes for a near doubling of performance at the same power level on hot days in the high desert.
PS- The line of temperatures on the display are: Incoming air, cooled air, HP refrigerant line, Suction refrigerant line, Water into BPHE, Water out of BPHE. The dT and KB (K Btus) are full accuracy. EEV position is 300. Ill try to find and add one more photo. The difference between the displayed watts and volts times amps is due to power factor. An inverter must provide the full VA, not just the "real" watts so I should change my display to that.
PPS- The Control box with Arduino Nano is squeezed in next to my propane (backup) water heater. I used all standard drivers for the power and temperature monitoring. The Dallas One wire software is very slow, about 1.5 seconds for updating all 6 sensors plus a bit of floating point math for that and the power monitor board but that's OK. Right now I have manual switches as inputs to the Arduino for controlling the EEV and power relays. By next summer, it will be automated. Te perf board left of the Arduino is just a 5V linear regulator and an analog circuit that senses water flow rate and shuts down the compressor power immediately if flow rate drops below 2 GPM; that assures no water freezing and the resulting wrecking of the heat exchanger.
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As Clint Eastwood would say in a low tone voice...."Oh, yea"....
Bruce,
Looks amazing. I'm glad you got it going !
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Thanks!