solar water heater- copper or black painted cpvc?


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Old 12-12-09, 11:56 PM
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solar water heater- copper or black painted cpvc?

alright, just bought my first house and am looking at ways to lessen my utility bills.

Im going to make a low profile roof mounted box that is mirrored on the bottom, have some sort of coil inside, with a glass top. I am going to get a cheap solar fountain kit so that the pump is only going when the sun is out to heat the water, when theres no sun, the pump stops. I am going to have a check valve to stop any water flow at night. I am going to have a t at the hot water out and cold water in at the water heater to feed the coil. and I am going to have ball valves on those as well as a ball valve on a drain setup so that in the freezing months I can close both lines to the coil, open the drain and let it out into a 5 gallon bucket to use for trees, animals, something...

that way I can also drain it when I get home from work, and then close the drain/ open the other 2 when I leave in the morning. even when its cold out in the winter, if you stand at a window or in a car, the sun really warms you up, its just the chill of the wind that really does it, so it should still work in the winter, theres just the risk of freezing which is why I have the drain on it.

anyways, whats a better material for heat transfer, copper (would probably use the 1/4" flex stuff like to ice makers/swamp coolers) or 1/2 cpvc painted flat black. I am thinking even if black cpvc could be around the same, the copper would be better because of its overall smaller capacity and a greater percentage of water in the tubing will be touching an exterior wall, and also less cold in the middle to mix with, so the smaller stuff should output warmer water to the water heater tank.

I know its very optimistic, but if I can save around 8-10 bucks a month in hot water, it can pay for itself in about 3-4 years(doesnt sound that good but the lower bills there after will be nice anyways)
 
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Old 12-20-09, 05:29 AM
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Better use the copper, in a closed mirrored box you might generate too much heat for the cpvc. I would also use at least1/2 inch copper, the smaller tubing will not flow enough water to make a difference. Are you planning to circulate water from your water heater thru the coil, or is this a one pass from the supply to the point of use?
 
 

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