(2) 4x12 Solar hot water panels...now what to do with them

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Extreme DIY Homeowner
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South of Boston, MA
Picked up 2 free 4'x12' solar hot water panels off Craigslist for Free
They seem to be in pretty good shape
The Recirc water heater tank failed, panels are good
Only Mom (older) at the house so Son wanted the panels gone

I'm debating on how to use them
Glycol w/recirc tank would cost $$....not sure how much, over $800 ?
Plus the controls etc

Pipes are Alum, thought of using them to heat the pool
But not sure if the chlorine would damage the pipes ?
---the "white" rust...?

Another option would be to use (1) to heat my hot tub in the summer
2nd one to heat water going to the water heater
Another thought was to use glycol & connect these to some extra radiators to help heat the house
But then what do I use it for in the summer ?
Drain the glycol...and use for hot tub & direct to HW heater ?

Ideas....thoughts ?


In the trades
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Whatever you use them for, don't run 'em open loop (to either a hot tub or a pool) or you'll wreck the aluminum.

Stagnation temps can be quite high- design the system with safety in mind or you risk taking a 200F+ glycol shower if a pump should fail to kick on or some obstruction develops, or you underdesigned the heat exchange/storage on the extraction end.

Low temp pre-heat for domestic hot water is pretty easy to hack with surplus panels and you have plenty of panel area to do it. Check out some of the DIY stuff they get into at builditsolar.com. See: http://www.builditsolar.com/Experimental/PEXColDHW/Overview.htm You could probably keep staganation temps under control by mounting them more steeply than recommended for max-annual gain, and use PEX heat exchangers in a high mass tank (rather than open loop drainback the way Gary Reysa did his homebuilt) for both the DHW and glycol loop. By running it with low temp high-mass storage, as preheat to your hot water heater you get a HUGE solar fraction, and very high efficiency on the panels. You'll need to read up on how to properly set up purge, charge & pressurize the glycol loop, but there's little rocket science involved.


New Member
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Biloxi, MS
I would use them for domestic hot water as well - That's going to be the biggest bang for your buck . . . . typically a quater to a third of all your home energy use

Buy a 10 gallon drainback tank and hook the panels to it and the tank to your existing water heater. Probably cost you around $2500 to do a first class job of it and likely Uncle Sam will reimburse you for half of that or more - If so, you'll have a very short payback of just 2 or 3 years

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