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. 

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. 



 

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. 

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.

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.

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.

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.

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.