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Old 11-09-12, 12:45 PM   #1
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Default Homemade Heat Pump Water Heater (R290)

I've Started on my new project, home made heat pump water heater. This project started as a metal recycling trip. I was loading up scrap steel into my dump truck when the neighbors noticed what I was doing. They came over and asked if I could take various things in as well. I ended up keeping two non working dehumidifiers and 3 hot water heaters. The HWH I'm using first is a GE 30 gallon electric unit. I lucked out in the fact that this unit uses just 1 4000 watt heating element on the bottom port. Apparently they made models with two elements with the 2nd being in a port toward the top of the tank. But instead they just installed a steel plug.
So first thing I've done after flushing and checking for leaks, was take out the plug in the top port and drill two holes thru it and tap them for 1/8"npt. Then I installed two 1/8"npt to 1/4"compression fittings in those holes. Next I bought 30' of 1/4" copper tubing and made a fairly sharp bend at the half way point and snaked 25' worth of it into the tank. Which was no easy feat, but persistence paid off. I then ran the ends of the tubing thru the plug and fittings and pretwisted the tube in the counterclockwise direction. Then threaded the plug back on, and snugged up the compressin fittings to make a watertight seal.
Last night I tapped into one of the dehumidifiers and found out it has nearly no r22 left in it. So I acquired some r22 and gauges, pumped in some refrigerant and the unit came back to life.
But never being happy with something normal, I grabbed a old propane torch, took the top off and brazed on a 1/4" flare fitting.
This morning I removed the r22 from the dehumidifier and hooked up my vacuum pump to the system for a half hour. I then took my new propane "torch" and refilled the unit with propane strait out of the Coleman bottle. The unit came back to life. On the r22 it was using 435-450 watts on R290 it's using 365-410 watts. This is where I'm at now. Next step Is to drain the system and plumb the coil in the HWH tank into the lines on the dehumidifier replacing to hot side HX. I'll try to figure out how to post pics. I don't have a computer hooked to the Internet, only my iPhone, and I'm not sure how to get photos uploaded.

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Old 11-09-12, 01:34 PM   #2
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[IMG][/IMG]Here is a pic of the HWH plug with the HX tubing going thru it.

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Old 11-09-12, 01:39 PM   #3
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Here is my torch conversion.
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Old 11-09-12, 03:20 PM   #4
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Dehumidifier running on propane!![IMG][/IMG]

And getting nice and cold

[IMG][/IMG]
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Old 11-10-12, 08:13 AM   #5
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I'm interested! I have been watching on the forum for someone to attempt one of these, and up to now the only one who seems to have completed a project is ac hacker. He converted his unit to water on both sides, to run off his ground source loop. Xringer threw in the towel when he found a premade unit. Both have posted awesome efficiency numbers and general satisfaction with their results. So I am eager to see a hacked unit brought to a new life.

Now, a few questions.
What model or capacity is your dehumidifier? It seems that for DHW production, 6000 btu is all that is necessary.
What's your plan on frost control? These units are designed so that the evaporator will freeze up under room temperature PDQ. They then defrost, sucking more water out of the air while the ice melts. Good for drying the air, not so good for max heat output.

Good luck and godspeed!
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Old 11-10-12, 10:14 PM   #6
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Quote:
Originally Posted by jeff5may View Post
I'm interested! I have been watching on the forum for someone to attempt one of these, and up to now the only one who seems to have completed a project is ac hacker. He converted his unit to water on both sides, to run off his ground source loop. Xringer threw in the towel when he found a premade unit. Both have posted awesome efficiency numbers and general satisfaction with their results. So I am eager to see a hacked unit brought to a new life.

Now, a few questions.
What model or capacity is your dehumidifier? It seems that for DHW production, 6000 btu is all that is necessary.
What's your plan on frost control? These units are designed so that the evaporator will freeze up under room temperature PDQ. They then defrost, sucking more water out of the air while the ice melts. Good for drying the air, not so good for max heat output.

Good luck and godspeed!

Thanks for the encouragement,

You have some good questions that I'm not sure of the answers at this point. As far as frost control goes, I'm just going to initially just wait and see what happens. The dehumidifier has the cooling HX and the heating HX. I'm going to loop the cold to the hot essentially doubling the area on the cold side hoping it won't get quiet as cold. I disconnected the fan last night to see if the hot side would reach a usable temp to heat water. During normal operation with the fan on it was only reaching about 90 deg. And the cold side was below freezing. After disconnecting the fan I saw temps in the 140's on the hot side and climbing and the cold side was in the 34-38 range. So between the doubling of the HX space and the temp range increasing I'm hoping that freezing wont be as big an issue. I currently have a GE Heat Pump water heater that works great. Ive never noticed it going into a defost cycle. It may do it, I'll pay more attention in the future. I probably should pull the cover off and see what it looks like under there. I didn't have a chance to play with anything today, I had a rifle match to lose. I'll start replumbing tubing tommorrow.

Hv23t

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Old 11-10-12, 10:18 PM   #7
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Old 11-12-12, 03:55 PM   #8
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Default R290 Smell

Just an observation. I just drained the propane out of the dehumidifier so I could make the mods to the plumbing. The filter/dryer in the system took nearly all the sulfur smell out the propane. I didn't smell it at all, until I brought the hose up near my nose, and even then it was just a faint smell. Maybe if it had been in there longer it would be completely gone.
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Old 11-12-12, 08:00 PM   #9
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Got a late start today, so I didn't get as much done as I was hoping. I did finish all the plumbing and I vacuum'd out the system but didnt have time to recharge it, or insulate the lines. But here is where I'm at.
[IMG][/IMG]

[IMG][/IMG]

[IMG][/IMG]
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Old 11-13-12, 02:08 AM   #10
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Hv23t Wrote:
Just an observation. I just drained the propane out of the dehumidifier so I could make the mods to the plumbing. The filter/dryer in the system took nearly all the sulfur smell out the propane.

When I was working on my GSHP I found the same. The propane became odorless. Your project looks great. I'm on the edge of my seat for the performance figures. We'll have to see if the eco-renovated propane enhanced water heater can give Xringers A7 any competition for operating costs.

Keep up the good work

Randen

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