Solar Hot Water Systems - PV vs delta T control [RE-wrenches]

[Allan Sindelar]

Todd,
    I'm concerned with your 2-pump-on-1-PV-module approach with a 10HEH
Hartell. I was told that Hartells, being brushless DC and
electronically-controlled, have a voltage tolerance limit of 17 VDC. I would
think you'd exceed that anytime only one pump was running, and it would be
worse in cold temps. We put a couple of 2-ohm resistors on a couple of
oversized modules recently, in order to drop voltage for safety. Have you
had any problems?
Also, which differential controller? Is it powered off battery DC, or is it
PV-powered, or is it AC?
Allan @Positive E

----- Original Message -----
From: "Todd Cory, Mt. Shasta Energy Services" <toddcory at jps.net>
> I have a 2 pump glycol system, and it is run PV direct. The glycol
circulation pump is DC, pv
> direct. The potable side of the loop also uses a DC pump off the same PV
panel, but is
> switched through a differential controller. Works great.

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