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IdleMind · 02-13-17, 03:01 PM

This little HP has been up and running for 2 months, I've just been lazy about posting how I finished it up. It's been a lot of trial and error. When I last posted I was trying to get a TXV to work but I never got COP much over 1.0. So swapped in & out compressors & various cap tubes. Then I got rid of the dehumidifier evaporator and replaced it with a coil of copper tube in a 5 gallon bucket of water. I also replaced the compressor with a small refrigerator compressor. I set it up so I could swap my various cap tubes in & out with flare connections. By chance more than science I eventually got it working to my satisfaction. I kept lots of COP data along the way so I could make good comparisons of various cap tube sizes vs performance. Here's a photo of my test set up.

Then I glued together sections of thin wall 4 inch pvc tube & filled with 6 gallons of water as the working heat source. I also coiled up about 15 feet of 1/4 copper tube to insert into this pvc tube for the evaporator. Here's a photo of the evaporator.

And here's how it looks up & running.

This only feeds the hot water to the bathroom sink. It's located so that I needed to plumb about 8 feet of water line to where it joins the pipe right under the sink. I used 1/4 copper tube to keep the volume of water in the pipe low so it it would deliver hot water quickly. I measured the faucet flow rate before the change (1.6 gpm) then with the restriction for the small tubing it dropped to 1.3 gpm which works really well.

It draws between 250 & 290 watts. When run on the resistance heater it draws 1450 watts. Where it is installed it is on an original circuit with and old screw-in 15 amp fuse. There is enough other stuff on the circuit that I could not use the resistance heater. So besides being more efficient, I don't have the electric capacity for a resistance heater anyway.

Now that I have the kitchen & bathroom sinks both with small heat pumps, I can turn off the main 40 gallon gas water heater except for 15 min before using the shower.

A few more notes on the passive heat source. The last month is about as cold as it gets and the basement temp has been at 55F. The water in heat source runs between 50 & 52F. When the heat pump is running it can drop down to 45F, but only right near the evaporator coil while the temp out of the evaporator gets down to 30/32F. In the summer when the basement air gets up to 65/70, it should work even better.

02-13-17, 03:01 PM	#28
IdleMind Helper EcoRenovator Join Date: May 2016 Location: SE Wisconsin Posts: 55 Thanks: 3 Thanked 14 Times in 10 Posts	This little HP has been up and running for 2 months, I've just been lazy about posting how I finished it up. It's been a lot of trial and error. When I last posted I was trying to get a TXV to work but I never got COP much over 1.0. So swapped in & out compressors & various cap tubes. Then I got rid of the dehumidifier evaporator and replaced it with a coil of copper tube in a 5 gallon bucket of water. I also replaced the compressor with a small refrigerator compressor. I set it up so I could swap my various cap tubes in & out with flare connections. By chance more than science I eventually got it working to my satisfaction. I kept lots of COP data along the way so I could make good comparisons of various cap tube sizes vs performance. Here's a photo of my test set up. Then I glued together sections of thin wall 4 inch pvc tube & filled with 6 gallons of water as the working heat source. I also coiled up about 15 feet of 1/4 copper tube to insert into this pvc tube for the evaporator. Here's a photo of the evaporator. And here's how it looks up & running. This only feeds the hot water to the bathroom sink. It's located so that I needed to plumb about 8 feet of water line to where it joins the pipe right under the sink. I used 1/4 copper tube to keep the volume of water in the pipe low so it it would deliver hot water quickly. I measured the faucet flow rate before the change (1.6 gpm) then with the restriction for the small tubing it dropped to 1.3 gpm which works really well. It draws between 250 & 290 watts. When run on the resistance heater it draws 1450 watts. Where it is installed it is on an original circuit with and old screw-in 15 amp fuse. There is enough other stuff on the circuit that I could not use the resistance heater. So besides being more efficient, I don't have the electric capacity for a resistance heater anyway. Now that I have the kitchen & bathroom sinks both with small heat pumps, I can turn off the main 40 gallon gas water heater except for 15 min before using the shower. A few more notes on the passive heat source. The last month is about as cold as it gets and the basement temp has been at 55F. The water in heat source runs between 50 & 52F. When the heat pump is running it can drop down to 45F, but only right near the evaporator coil while the temp out of the evaporator gets down to 30/32F. In the summer when the basement air gets up to 65/70, it should work even better.