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

[Todd Cory, Mt. Shasta Energy Services]

The Hartell brushless DC motors are rated at 30,000 hours. Their brush version
is rated at 7000 hours. 30K is basically the bearing life... and when  run for a
yearly average of 5 hours a day = about 16 years... long time.

Todd


"Tom Lane, Energy Conservation Services" wrote:

> 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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--
Todd Cory
KE6SXS
toddcory at finestplanet.com
Mt. Shasta Energy Services
License C-10 # 811428
P.O. Box 689
Mt. Shasta, CA. 96067
(530) 926-1079

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