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Old 09-08-09, 10:39 PM   #3
Daox
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A PV powered pump will work okay. However, it will start up before the panel has warmed up and it will shut off after the panel has already cooled down. So, you will loose some efficiency.

With a normal thermal differential pump, you set it so the pump only comes on if the solar panel is 8 or more degrees hotter than the water tank. You also shut it off when the solar panel is only 4 degrees (sometimes more) hotter. These temperature differentials are set to compensate for thermal losses through the lines. The longer the line between the tank and collector the greater the temperature differential. It of course matters how much insulation is used around the lines as well. In the commercial controllers, these temperature differentials can be set to as much as 24 degrees.
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Last edited by Daox; 09-09-09 at 09:48 AM..
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