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Converting radiant floor heat from AC to DC - Page 2

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Posted by nicksanspam on February 25, 2005, 10:56 am

I wonder how much. it seems to me that equivalent AC and DC motors use
about the same power.


Posted by Scott Loupin on February 25, 2005, 1:14 pm
I'll bypass the inverter, so I won't lose the battery energy.  Not sure if a
DC motor is any more or less efficient than an AC one, anyone got
measurements/websites with this info?


Posted by DJ on February 25, 2005, 2:32 pm
Scott Loupin wrote:

sure if a

Nick has a good point: they aren't always more efficient. Stuff like
ThermoDynamic's DC "solar pumps" (www.thermo-dynamics.com) are VERY
efficient, drawing a dozen or so watts for running 3gpm pumps. Not
free, though...

You're going to have to go on a "case by case basis" when picking


Posted by Ecnerwal on February 25, 2005, 3:07 pm
 It's very much specific cases, and whether it's worth doing will depend
a great deal on what you currently have - but there do seem to be many
highly inefficient AC-motor circulator pumps in the wild.

I did most of my looking at this a year ago, and will need to revisit it
when I get to the point where I spend money, but for the same flow &
head, I could get about 90-120 watts DC, and 250-350 watts AC. For
something that runs as much as a radiant heat circulator, that's a huge
difference; Especially since they run the most when your power in is
poorest (winter).

The evidence of my shopping thus far is that AC circulator pumps and
electrically efficient motors do not seem to be conjoined as often as
they are on DC circulator pumps, since work out the far end is basically
the same. In principle, other than inverter losses (again, not
insignificant for something that runs this much), there's no reason an
AC motor could not be just as good, but in practice, evidence would
suggest that the AC motor is making a lot more waste heat out of your
electricity, in most cases.

The best thing would probably be to get an actual measurment of the
power the current pumps use, and compare that with what you are
considering for replacements. If it's close, you may do better to leave
the heating system alone and add more power in (another panel) with the
money you would have spent on new pumps.

Cats, Coffee, Chocolate...vices to live by

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