Replacement Indirect Solar Water Heater Tank?

Q: My house has a solar water heater installed by the previous owners. The tank is dying (leaking on my laundry room floor) so I will be bypassing it as soon as I have a free evening. Question is, I've been doing some looking around online, I can't seem to find a replacement tank that would make it worth my while to keep the system installed. Ones I've found are >$1K and I just don't think that it's saving me that much on my gas bills. I have a very shady lot and I haven't ever seen the output temp of the solar tank over 90F. Can someone tell me where is the best deal on a replacement tank? also, how to refill the loop between the tank coil and the collector? it's a pressurized system with antifreeze, running at about 20 PSI. Also, is there a good deal out there on a controller with thermocouples? PO's had the pump just running on a time switch which I think is probably part of the problem, on an overcast winter day it might actually be shedding heat to the outside rather than heating the water.

A: The solar tanks with internal heat exchangers tend to be expensive. You might go with a regular electric hot water tank as the storage tank, and use an external heat exchanger. Or, change over to the Butler type system that uses the existing hot water tank for both storage and back up heating (search for "Butler" on this page: http://www.builditsolar.com/Projects/WaterHeating/water_heating.htm). For instructions on refilling the system, go to the same page as is listed above, and see the Home Power article on closed loop systems -- "Solar Hot Water for Cold Climates, Parts I and II, Ken Olsen and Tom Lane" Gives a very detailed, hands on description of closed loop systems -- including how to install. Two common differential controllers are the Goldline GL-30, and Steca 306(?). I use both, and (I think) they are both good. The Steca has a nice little LED screen that tells you whats going and and gives tank and collector temps. Both are in the $150 area with sensors (which are thermistors). Lots of places carry them -- e.g. King Solar, ebay, ... You definitely want a differential controller -- its just not possible to do this manually. Big list of suppliers here: http://www.builditsolar.com/References/supplierrefs.htm A few tanks listed here: http://www.builditsolar.com/References/Suppliers/SolarHeating.htm#Sto... If you wanted to tackle a fairly large project, you could convert your system to one like this: http://www.builditsolar.com/Experimental/PEXColDHW/Overview.htm Not saying this is a good way for you to go, but just one more option.

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