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Old 02-19-10, 11:11 AM   #2
Daox
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Hello and welcome to the site!

I think your current setup is superior to what you are describing going to. The point being that you always want your heat exchangers subject to the largest delta T (difference in temperature). By placing the heat exchanger at the bottom of the water tank, it is always subject to the coldest water. This means more heat will get transferred from the glycol to the domestic water. This cools the glycol down more and means when it passes through the solar collector it will also absorb more heat. The net effect is more heat transferred and a more efficient system.

With the natural convection external heat exchanger, by the time the water gets to the upper portion of the exchanger, its already decently warm and the heat transfer isn't as great. You can get the same heat exchange, but you'll need a larger exchanger for this style.

I would definitely look into putting a timer on your electric heating element though so it doesn't kick on until you actually need hot water (likely only in the early morning as the solar will keep it hot during most other times). A tankless heater is a great alternative.
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