Heat Pump Water Heater - Coil in Tube

[vwhead77]

Originally Posted by Ron342

The temps you show are in and out refrigerant temps at the condenser not water? Wonder how it would act if you pushed it to 130 F high side. But 20 psi suction seems low = -6 degrees F. Did you just add charge til the amp draw increase leveled off or??
I have a 3/4 ton ebay txv for mine - it was $25 shipped but it is external equalized and I know nothing about txvs!
I wonder why no one seems to use r134 in these - is the oil not compatible - the p/t seems better.

Yes those are in/out temps. I had to charge the unit by amp draw since it over charged very quickly trying to go by temp/press for 209a. Very strange readings but I'm thinking it's because my condensing side is exposed to hot water not cool water. Heating the water is the main concern and the evap side isn't freezing over so I'm going to watch it - my other concern now is getting enough cool gas back to the compressor. I know what you mean about the 134a- I had thought about converting (dumping mineral oil adding PEO) I still may do that just to see how it acts. As I say, I'd really like to see a better low side reading if possible.

[randen]

VWHead77

The suction side 20psi is around the pressure I settled with for the HPWH I made for my parents. You can check my post: Another heatpump water heater. by Randen.

It has been purring along nicely for more than a year.

I too had added charge only to get the heat set on the condenser side. I had found by experimentation that running higher pressures didn't increase the heat out-put just increased power draw. I used both a clamp amp meter and a receptical watt meter to tweek the charge. I believe if my memory serves me right its costing my parents about $15/ month This is beating out their costs of $22/month rental coupled with the propane cost to heat the water. They are extremely happy with it. They did notice right away the lower temp of the water as its only about 104 Deg F. Fine for showers. and why would you need hotter.

Is the refrigerant you used propane?? R290.?? That what I had used and that's what the lower suction pressures are about.

Good work on your build.

Randen