DC Pumps [RE-wrenches]

Travis Creswell, Ozark Solar ozsolar at ipa.net
Sat Jun 30 06:15:57 PDT 2001


Morning Hugh,

Tell me more about this "inverter" device you speak of?  Perhaps it rights
things that are upside down?  How can that move hot water?  Surely you will
explain more as I am only a simple hillbilly easily confused by such
technical terms.
but seriously..

Although it's not what you would think, hydronic heating systems tend to use
a lot more electricity than an off grid house can regularly generate in the
winter.  The outdoor boiler systems are designed to have the circ. pump run
24 hours/day.  There is ways around that but it still runs over 12 hrs/day
when it's really cold.  That's nearly 2 kWh's for regular AC pump.  Even a
super efficient DC pump will need nearly 1000 watt hours/day   The zone
pumps plus the transformers for controls easily consume another 2000 watt
hours a day.  When does the system need the most electricity?  The shortest,
darkest coldest times of the year.  So even with DC pumps the systems that
I've looked at doing were going to require regular generator run time (fed
to the inverter to charge the batteries to run the pumps) to come up with
the 3 or more kWh's for the hydronic system.  That's 3 kWh's before the
first light bulb or any other load is turned on.  In my area this last
December averaged 3.1 sun hrs per day.  I don't know about others but for me
a system that would produce over 3 kwh's in the winter is pretty big.

Jeffrey,  how many watt hours are you calculating you are going to need to
run your hydronic system?  What is the avg. winter sun hrs where this system
is going?


Travis Creswell
Ozark Solar


----- Original Message -----
From: "hugh piggott" <hugh.piggott at enterprise.net>
To: <RE-wrenches at topica.com>
Sent: Saturday, June 30, 2001 1:45 AM
Subject: Re: DC Pumps [RE-wrenches]


> >I have been faced with this several times and the only solution that the
> >customer would buy was running the generator vs. paying gobs extra for DC
> >pumps amd more zones becuuse of the small capacity of the DC pumps.
> >
> >Well I only had more questions and no answers.
>
> Isn't there a new-fangled gismo you can buy nowadays called an 'inverter'?
>
> Or am I missing something?
> --
> Hugh
>
> http://www.ScoraigWind.co.uk
>
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