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Old 07-30-10, 09:19 AM   #1
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Default Mike B's Solar Pre heater

Well I decided to take the plunge and do a solar water heating project. I built the basic solar panel using the wonderful wealth of knowledge at builditsolar.

2in foam backer, then 1in. piece of higher temperature polyisocyanurate with aluminum on the front. 1/2 plywood to staple to, 1/2in copper tube to a 3/4 manifold. With roof flashing wrapped around the 1/2in pipe as a collector painted with flat black grill paint. A piece of plexiglass on top.

All this plumbed in PEX to my basement trough drain tile filled with great stuff.
I used shark bites at the interface of my garage roof so I could take it a part if I needed to. (this has an added effect that when the pump is off it causes air to leak into the system and drains back to my tank in basement)

I have a 55gallon steel paint barrel in the basement. With a barrel liner so maybe the barrel wont rust out. That is wrapped insulation where ever possible. The out going water pulls off the bottom of the tank. The incoming comes in at the top with a T pex fitting so it doesn't stir the water as bad.

Then i have three 20ft 1/2 in soft copper lines sweated to a 3/4 "manifold" submerged in the barrel. That carries my now pre-heated potable water into the water heater.

I used a Make Controller to control the system. Many 1-wire sensors : solar panel temp ; barrel temp ; outside temp ; attic temp(for fun) ; basement temp (for fun) are logged to two different database servers. The Make Controller has built in ethernet, 3 serial ports, and plenty of I/O. Not quite as large a user base but every bit as helpful a support system. 1-wire allows me to use cheap sensors and a familiar cable that runs long distances without problem.

The make controller turns the pump turn on when ever the solar panel is 20deg warmer than the storage tank. I hoped that the heat losses in the pex will be made up for in the differential and the pump wouldn't run as long. I have the controller send the temps to the database servers every 3min.

When I am able to post links I will.

Not a perfect system. But you can see when the temp drops in the storage barrel that is normally a shower. You can also see the temp rising when the pump is on. I have only had the pre-heating going for a couple weeks so i don't know what i am saving/costing my self yet.

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