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IdleMind · 10-12-16, 01:20 PM

This is my second small heat pump water heater build. I am starting with a 6 gal 110v electric water heater that I found on craigs list for $45. I have 2 dehumidifiers in my basement. One is about 13 years old and uses r22, the other is about 5 years old and uses R410a. The older one has lousy performance compared to the newer one as measured by water removed per watt-hour. Perhaps the newer one has a better control system. Anyway I am using the old one for this project.

The first step was to grind off the scale from the steel bottom and then tin it with an acid core solder. Here's a photo after tinning.

I am soldering a coil of 3/8 copper tube to the bottom of the heater. I started with a 20 foot coil and got 15.8 feet of working coil soldered in place. My first build had only a 2.5 gal tank which wasn't big enough to put the coil on the bottom. On that one I used about 18 feet of 1/4 copper tube soldered to the side of the tank. I think this will be much better. Here it is after taking outside and washing off the flux residue.

Next I covered the coil over with silicone caulk as a first layer of insulation.

Then I reattached the top & bottom covers and injected with great stuff, I kind of over did it, the covers buckled out a bit as it expanded and cured.

I have the dehumidifier modified so more photos to come soon.

10-12-16, 01:20 PM	#1
IdleMind Helper EcoRenovator Join Date: May 2016 Location: SE Wisconsin Posts: 55 Thanks: 3 Thanked 14 Times in 10 Posts	Hpwh 2 (heat pump water heater #2) This is my second small heat pump water heater build. I am starting with a 6 gal 110v electric water heater that I found on craigs list for $45. I have 2 dehumidifiers in my basement. One is about 13 years old and uses r22, the other is about 5 years old and uses R410a. The older one has lousy performance compared to the newer one as measured by water removed per watt-hour. Perhaps the newer one has a better control system. Anyway I am using the old one for this project. The first step was to grind off the scale from the steel bottom and then tin it with an acid core solder. Here's a photo after tinning. I am soldering a coil of 3/8 copper tube to the bottom of the heater. I started with a 20 foot coil and got 15.8 feet of working coil soldered in place. My first build had only a 2.5 gal tank which wasn't big enough to put the coil on the bottom. On that one I used about 18 feet of 1/4 copper tube soldered to the side of the tank. I think this will be much better. Here it is after taking outside and washing off the flux residue. Next I covered the coil over with silicone caulk as a first layer of insulation. Then I reattached the top & bottom covers and injected with great stuff, I kind of over did it, the covers buckled out a bit as it expanded and cured. I have the dehumidifier modified so more photos to come soon.