Hpwh 2 (heat pump water heater #2)

IdleMind · 10-31-16, 01:03 PM

A few days ago I charged it and experimented with settings to determine charge amount, fan speed, and txv adjustment. At end of day I had charged with approx 2.70 oz of propane, 3.5v power to fan, and had turned out the txv adjuster screw 2 turns to increase flow to evaporator. The txv adjuster never made much of a change in SH, perhaps the txv is too big for this small compressor. Although it did the job as good or better than the cap tube.

After setting over night to stabilize, I started it up and took this data.
At 13 min the bottom 3 evap tubes were frosted over, and by 19 min they had thawed out. By end of the test the compressor case was up to 197F which I consider on high end of acceptable.

I thought the fan was running too slow and that if I speeded it up it would increase SH and lower SC. So I cooled down the water and changed the fan power supply from 3.5 to 9 volts and took following data.

Only the bottom tube frosted briefly before thawing. It performed better at heating water. The SH responded like I expected, but the SC did not change much. Maybe the condenser is just too big for the compressor.

Not sure about next step, maybe let out some propane. But I have a very old 8000 btu window AC that is not being used, so I could try its compressor just as an experiment.

10-31-16, 01:03 PM	#21
IdleMind Helper EcoRenovator Join Date: May 2016 Location: SE Wisconsin Posts: 55 Thanks: 3 Thanked 14 Times in 10 Posts	A few days ago I charged it and experimented with settings to determine charge amount, fan speed, and txv adjustment. At end of day I had charged with approx 2.70 oz of propane, 3.5v power to fan, and had turned out the txv adjuster screw 2 turns to increase flow to evaporator. The txv adjuster never made much of a change in SH, perhaps the txv is too big for this small compressor. Although it did the job as good or better than the cap tube. After setting over night to stabilize, I started it up and took this data. At 13 min the bottom 3 evap tubes were frosted over, and by 19 min they had thawed out. By end of the test the compressor case was up to 197F which I consider on high end of acceptable. I thought the fan was running too slow and that if I speeded it up it would increase SH and lower SC. So I cooled down the water and changed the fan power supply from 3.5 to 9 volts and took following data. Only the bottom tube frosted briefly before thawing. It performed better at heating water. The SH responded like I expected, but the SC did not change much. Maybe the condenser is just too big for the compressor. Not sure about next step, maybe let out some propane. But I have a very old 8000 btu window AC that is not being used, so I could try its compressor just as an experiment.