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

[Tom Lane, Energy Conservation Services]

DC pumps require precise matching of the amperage voltage curve of the  PV
module curve to the real motor requirements of the  DC  motor --the reason
you are having problems is that you do not know how to match  THE  pv module
to the DC  motor--the march WILL last 15 years PLUS   if the pv module is
not over 16 volts AND the amperage is not over 1,4 amps -- the brushes will
ride on an air  if you over power the 12 volt motor   gator tomGlobal
Resource Options" <jeff at globalresourceoptions.com>
To: <RE-wrenches at topica.com>
Sent: Wednesday, April 09, 2003 10:08 PM
Subject: RE: AC circulator vs. PV driven DC [RE-wrenches]


> 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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