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. 

My custom 120VDC battery charge management system was designed for 10- 12V AGM batteries in series, and has individual battery shunt regulators so that variations in batteries don't matter, and less equalization is needed.  I used cheap lead-calcium batteries (marine "deep cycle") initially for testing, and found that due to my very low average DOD, I was getting 4.5 years of service life. AGM batteries never came down in price so I've left well enough alone.  These Everstart (Johnson Controls) Marine batteries are stocked at the local Walmart.  They use so little water that I top them off annually, needing about a gallon of distilled water.  Low water use is one of the characteristics of lead-calcium.  They also have very low bulk taper charge characteristics similar to AGMs; as they become full, the charge current goes to well below 0.1 amps, typically below 0.050 amps.  This helps explain the lack of water use. 

I just added a T105 type (floor polisher battery - again "Everstart" by Johnson Controls though Walmart) 6V battery to my welder and am shocked at the difference in charge current.  The bulk charge current NEVER goes below about 2.2 amps, even if left on the charger, full, overnight.  I thought something must be wrong until I checked the Trojan data; they expect 2-3% of the C/20 to be the lower limit of charge current! 

I never fully technically appreciated the lead-calcium "Marine" batteries as I should have, since I was comparing them to AGMs and not wet lead true deep cycle batteries.  ( I use a 110AH AGM for my small 12V supply; I found 12 and 120V to be a very useful combination of home power). As long as you can keep your DOD below 20%, the lead-calcium seem to have good lifespan, good charge efficiency, very low water use.  They can also put out relatively high current, as I've found for the welder.   For my 120VDC system, currents are below 15A, usually well below that, which greatly improves effective capacity and efficiency.

It has been very educational to see how the T105 type 6V battery compares in a series application with the Marine (lead calcium) batteries.  While I have no doubt the T105 types will outlast them for the DC welder application, it gives me new appreciation for the Marine type batteries where DOD can be kept to modest levels for an expected service of 4-5 years.

My neighbor Jeff is the owner of the Propane modified CS from DES. He's been running it for the last 4 years with no troubles.  He mentioned he was having reduced power- couldn't carry both well and washer at the same time.  I suggested he check valve timing, as we had twiddled those to reduce exhaust/intake overlap to reduce propane smell in the engine room.  He did, and found that our extended push rod for the intake had failed. We had added 0.5 inches of aluminum spacer under the cylinder to reduce compression, so the longer exhaust rod worked fine for intake but former short exhaust needed a couple inches added. I had done weld bond kludge with some bits I had on hand; epoxied carbon fiber tube and added rounded end bit.  It had failed after 4.5 years, the carbon tube was now cracked as the ends pushed together, reducing the intake opening to only 4 mm from a normal 8mm.

I was thrilled to have a small welding project.  I had some rod of about the right diameter and welded on a new extension to the push rod. I used 7018 for the job, with some 6013 for finish filler.  It is very satisfying to have my new 24V battery welder put to good use, again. We installed it and reset the intake opening per the IO flywheel mark we put on (using 38AC's brilliant method), and now she's back to full power again.

My ST-3 is out, won't operate on the harmonic winding system either, and flashing the FC dinn't change anything.  I did use the generator yesterday and it worked fine.  So far I'm baffled. The static (off) testing of brushes and slip rings looks good, field coil resistance is OK, harminic winding resisitance is OK, stator resistance winding is OK, my other various switches, fuses and relays OK.

Came in for late lunch, meds, and a study of the circuit diagram.  The bridge diode is a modern 800V unit so highly unlikely to have failed. I'll have to start using my handheld o'scope with a 15 foot extended probe lead and see what's gone wrong with the spinning harmonic signal while I stand outside.  It's cold, cloudy and windy.

I had a failure of the 5 rpm gear motor actuator which I use to control my projector focus.  Focus control is needed as the Qume Q5 focus is not temperature stable. it's a 24VDC rated little can type brushed motor I operate on 12V.  It stopped working when it got cold, even at 40F the motor would not start.  I use a modifed 2 channel IR receiver to control the gear drive, since I already have IR extender control of the projector.

I took it apart the failed gear motor and found the motor, brushes and commutator are clean, and the motor starts and runs freely at 12v in both directions.

So I'm thinking that the black grease which covers all the metal gears, and the worm drive which is on the motor shaft gets so stiff in the cold that the motor can't spin up.  Spin up is not aided by the two pole commutator. 

I'm thinking of cleaning out the grease and putting a bit of ATF on the gears.  I'm also going to boost the voltage.  I think there's some 19 or 21VDC for the projector I can use. This is not a high stress application and it only runs for maybe 30 seconds a day.  Any other ideas?

I thought I should play nice and quite stuffing this in Glort's PV -grid tie work.  While I did add 1500 watts of panels to my existing 875 for this project, I'm now down to the inverter work.

A little review:

I live off grid and have lived with my own 120VDC system and Listeroid for AC and compressed air for a long time.  In preparation for adding inverter power to my system, I upgraded my 120VDC PV charge regulator to handle up to 3000 marketing watts of PV.  It's linear, not pulsing, for very clean DC.

My 120VDC input inverter design is based on the venerable Trace SW series which does low frequency switching of transformers with secondaries in series to create a sine.  That general concept is about all I'm using.  I'm using very soft (slow) switching plus snubbers and minimal passive filtration to generate AC with no audible (via AM radio) EMI on the AC or DC supply.  I'm only using 2 transformers of equal output secondaries, and they are used to make a 5 step sine wave; zero plus two steps up and two steps down.  I originally did a 7 step sine but found 5 step better. The 5 step sine gets the THD down below my ST3 generator head, and eliminates the typical 20% motor heating loss of a MSW inverter.  I use 120VDC for my home and shop power, and have been using a Listeroid 6/1 for AC generation for well pumping and washing machine.

I have previously done quite a bit of testing of the prototype on motor starting at 120VAC output; it would start a 1.5HP tile saw like grid power, instant and effortless.  I ran into a bunch of trouble when I switched transformers for 230VAC output; ultimately I tracked it down to huge inrush surge current.  Until I worked up a software solution of soft starting the transformers, I could only test by starting the processor and H-bridges with 0 volts input, then switching on the 120VDC through two huge chokes and 30K uF of DC filter caps. This provided a slowly increasing voltage which kept inrush current minimal. The massive DC filter was needed for keeping AC off my clean 120VDC. With the filter in place, I now have 1 millivolt of AC ripple with 1000 watts of load.  Backfeeding 230VAC to my step down transformer outside the shop, I've run a couple loads of laundry in the washer (about 1100 watt load also) with no trouble and barely warm heatsink on the H-bridges.  I've also been testing with 500, 1000, and 1500 watts of heat lamps in the shop.

I got the prototype jury rigged on the floor of the battery bank shed and then found that due to my new short 120VDC supply wires to the 10K uF fiter output capacitor, the old Antek transformer inrush current problem came back and bit me.  I should have tested with small fuses, but I got cocky...with 4 mosfets, 3 ICs, and 2 transistors fried the result.  I got it repaired, changed the soft start to extend from 50 usec to 5 millisecond pulses, and now she starts and stops nicely on small fuses, again.

Tomorrow I'll test on my 1/2 HP Franklin submersible well pump. It pumps from a depth of 200 feet.  It normally runs at 1150 watts, with starting peak over 3400.  The issue to be tested will be surge load capability and compatibility with the operation of the Franklin QD solid state capacitor start relay.

Thanks to 38ac I got connected with another member Robert Leonard, who had some SOM flywheels for sale.  Bob did a great job of securing them to a sturdy pallet and getting them loaded on my freight carrier 8 days ago.  Today I picked them up at my local helpful Ace Hardware.

They are now on my shop apron ready for some clean up and new paint! They are a bit shocking to a someone only familiar with Rajkot castings; there are no voids, putty, bondo!

I'd like advice on your favorite rust treatment that does not involve Rustoleum type oil based paint.  I just can't stand the stink of it. I'm thinking sand and wire brush, naval jelly, then paint. I'm in AZ, USA, so continued rusting is not a big issue, I'm just proud of them so want to pretty them up a bit.

I've been disappointed with the analog panel meters for AC frequency and voltage from China.  The frequency meters in particular are junk- when voltage goes down (with increased load and thus lower frequency), the frequency meters show an increase in frequency! Laughably bad design.

Many digital frequency meters have problems with the ragged waveform of the ST generator heads.  They will not display the proper value, or even close.

I did find one cheap ($10) digital meter that is quite good:

http://www.ebay.com/itm/131683950915?_trksid=p2060353.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

Both frequency and voltage are displayed properly and accurately on an  ST-3 head on harmonic.  Voltage is RMS, tracks a Siemens ($) display within a volt.