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Old 03-07-10, 10:10 PM   #23
Joe
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Quote:
Originally Posted by Trevor View Post
I know a couple of things would need changing, like the fact that I canít use PEX-AL-PEX for potable water so I would probably use 1/2Ē PEX with elbow on each end. I would also have to put a pressure release valve and probably an air vent at the top of the panel where the water exits. I would utilize the same secondary tank and circulator so I think I am looking at about $300 to create the panel with enough pipe to bring it into the cellar. Any thoughts?


I had a couple of links to show examples but it would not allow me to post them, so if you have a question on my design please email me or post a reply. Thanks
Hi Trevor, if you will be circulating potable water through it I would recommend you use the copper style collector as normal pex wont hold up. you will need a temp differential controller(turns pump on when collector is hotter then the tank and off when tank max temp is reached) and a pump designed to circulate pressurised water (gerfundos?) when max tank temp is reached the pump stops running and the water just bakes in the collector(stagnate condition) and can get up to about 200* or more in strong sun, and I don't know about you but I have 80 psi water pressure and that would put me right at the 200* 80psi limit of standard pex. I think what would work good for you is batch heater as long as you drain it before the freezing weather or just build the $1k drain back system and not use the extra hot water heater. This is right off Gary's site:
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It is easily bent in to tight turns AND it retains its shape without spring back. This is a very nice feature.

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It has higher working and burst pressures than ordinary PEX.
The PEX-AL-PEX I used (Mr. PEX) is rated for 160 psi at 200F.
Standard PEX is rated at 80 psi at 200F, and 160 psi at 73F.

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It has better thermal conductivity that regular PEX -- this should result in somewhat better heat transfer from the aluminum fins through the PEX to the water.
PEX-AL-PEX 3.1 BTU/h-ft F for half inch tubing
PEX 2.6 BTU/h-ft-F for half inch tubing

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It has a much lower coefficient of thermal expansion than PEX, and is more compatible with the expansion rate of the metal fins.

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It may be somewhat more tolerant of freezing. It will probably withstand several freeze thaw cycles, BUT will NOT withstand continual freeze thaw cycles.

so regular pex would be less efficient and wouldn't be a good idea to subject it to such conditions. By the way I have seen the pictures of the blown up wood stoves and they all didn't put a pressure relief valve in-between the shut off valves and the heat exchanger
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