AC circulator vs. PV driven DC [RE-wrenches]

[Jeffery Wolfe, Global Resource Options]

Peter,

If we had great DC pumps, I *might* go along with the DC recommendations in
this climate, but probably not.

We've gone almost totally away from the DC pumps. Either too small (ElSid
10) or too noisy (Hartell), or too much maintenance (March). Perhaps the
Dankoff are better, but they are still brushed pumps, and at 12V, do not
have great brush life. And who needs to remember to get the brushes replaced
BEFORE the collector stagnates?

Yes, AC grid failure can result in a problem with an AC powered pump running
off an AC powered diff temp controller. Guess we've found that to be less of
a problem than the DC pump non-power, PV panel covered by snow, PV panel
clear/solar thermal collector covered by snow, flat plate panel running at
low startup temps while full sun is on the PV, etc. problems.

Certainly for a larger system, getting enough DC pumping will be a
challenge, unless the tank and pumps are right at the collectors. This will
result in a "small plethora" of DC pumps and PV's. Just seems simpler to put
in an AC pump. And then when the unskilled plumber goes to "fix" it in 5
years, he'll have a clue. (Not an unimportant consideration.)

Enjoy spring!?

Jeff

-----Original Message-----
From: Peter Talmage [mailto:ptalmage at yahoo.com]
Sent: Wednesday, April 09, 2003 6:15 PM
To: RE-wrenches at topica.com
Subject: AC circulator vs. PV driven DC [RE-wrenches]



I am designing a solar heating system which will use
10  4'x10'collectors. I had planned to use a single AC
pump operated by a differential controller. The system
uses antifreeze so there is only modest head to
overcome. My customer likes the reliability of a DC
pump driven by a PV. I usually do this with small
systems, but this one would need 4 Hartell pumps to
get adequate flow, considering head loss. Anyone have
any thoughts ?  Thanks.

Peter

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