07-13-2008, 05:02 AM
It's because hot water heaters pull much more power heating water than in maintaining heat. Timers have been proven again and again to be ineffectual. Insulation is a much better bet.
As for coils on the roof or elsewhere, you're going to find natural convection to be not near as effective as having a small circulation pump in the systems. It's power draw will be minimal. If it's connected to a thermostat in the box, that's good. Solar collectors can get awful hot when the sun is cooking, and a lot of them suffer glazing and sealant failures. As well, remember if it gathers heat in the day it sheds it when it's rainy or cold out, too, and conductive loss from the water can be pretty significant.
As for coils on the roof or elsewhere, you're going to find natural convection to be not near as effective as having a small circulation pump in the systems. It's power draw will be minimal. If it's connected to a thermostat in the box, that's good. Solar collectors can get awful hot when the sun is cooking, and a lot of them suffer glazing and sealant failures. As well, remember if it gathers heat in the day it sheds it when it's rainy or cold out, too, and conductive loss from the water can be pretty significant.