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Xringer · 04-18-10, 11:14 PM

Using PV to directly heat the water is so simple. And will likely pay for itself in oil savings, pretty quickly.
Plus, the PV array will likely last for about 30 years with minimum upkeep.

I know all about glycol with corrosion inhibitors. That part of my old system wasn't a problem.
The fresh water side of the heat exchanger and the storage tank are where the leaks occurred. Our water eats copper.

My testing shows that about 240 watts of heat (819 BTUh) will cause
heat gain in my boiler, when set to summertime temperatures.

Having 4,000 BTU would be nice, but it could be capacity that I don't really need.
There are only two people living here.

~~~Edit 11,20,2010
I've found the reason I got heat gain with 240 watts.. I was heating the water at the top
of the tank.. Also measuring at the top of the tank.. Very misleading.

Last month, during good solar days, with about 5 hours in the 400-500 watt range,
there was no net gain. But the rate of loss slowed greatly. I think more PV is needed.
My guess is 800 to 1,000 watts of PV would work pretty well.

04-18-10, 11:14 PM	#20
Xringer Lex Parsimoniae Join Date: Feb 2009 Location: Woburn, MA Posts: 4,918 Thanks: 114 Thanked 250 Times in 230 Posts	Using PV to directly heat the water is so simple. And will likely pay for itself in oil savings, pretty quickly. Plus, the PV array will likely last for about 30 years with minimum upkeep. I know all about glycol with corrosion inhibitors. That part of my old system wasn't a problem. The fresh water side of the heat exchanger and the storage tank are where the leaks occurred. Our water eats copper. My testing shows that about 240 watts of heat (819 BTUh) will cause heat gain in my boiler, when set to summertime temperatures. Having 4,000 BTU would be nice, but it could be capacity that I don't really need. There are only two people living here. ~~~Edit 11,20,2010 I've found the reason I got heat gain with 240 watts.. I was heating the water at the top of the tank.. Also measuring at the top of the tank.. Very misleading. Last month, during good solar days, with about 5 hours in the 400-500 watt range, there was no net gain. But the rate of loss slowed greatly. I think more PV is needed. My guess is 800 to 1,000 watts of PV would work pretty well. Last edited by Xringer; 11-20-10 at 08:37 AM.. Reason: I was wrong!