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Messages - BruceM

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1
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. 


2
Everything else / Re: Bad Solar Panel
« on: September 15, 2021, 04:06:02 PM »
+1
On-off type charge controllers normally use panel shorting by an N-channel Mosfet as a means of charge regulation.  IT is harmless to the panels.

You got a dud, since you're getting 0V, likely an open connection to the cells.
As Fred8 notes, report the DOA, 0V in full sun.



3
Everything else / Re: DIY water chiller - reading suggestions?
« on: September 13, 2021, 07:20:30 PM »
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. 



 


4
Everything else / Re: DIY water chiller - reading suggestions?
« on: September 13, 2021, 06:02:41 AM »
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.

5
Everything else / Re: DIY water chiller - reading suggestions?
« on: September 13, 2021, 03:21:23 AM »
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. 

6
Everything else / Re: DIY water chiller - reading suggestions?
« on: September 12, 2021, 05:51:43 AM »
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.




7
Everything else / Re: DIY water chiller - reading suggestions?
« on: September 12, 2021, 01:24:49 AM »
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.






8
Everything else / Re: DIY water chiller - reading suggestions?
« on: September 11, 2021, 06:42:52 PM »
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! 


9
Everything else / Re: DIY water chiller - reading suggestions?
« on: September 11, 2021, 05:12:18 PM »
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.






10
Everything else / Re: DIY water chiller - reading suggestions?
« on: September 11, 2021, 12:50:19 AM »
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.






11
Everything else / Re: DIY water chiller - reading suggestions?
« on: September 10, 2021, 04:19:22 PM »
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.








12
Everything else / Re: DIY water chiller - reading suggestions?
« on: September 10, 2021, 04:42:24 AM »
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.







13
Everything else / Re: DIY water chiller - reading suggestions?
« on: September 09, 2021, 06:18:46 PM »
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.







14
Everything else / Re: DIY water chiller - reading suggestions?
« on: September 09, 2021, 02:25:48 AM »
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.






15
Everything else / Re: DIY water chiller - reading suggestions?
« on: September 08, 2021, 06:11:59 PM »
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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