DC heat? [RE-wrenches]

[David Katz]

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Hi Geoff,
AC water heating elements work fine for DC.  You just have to contacts 
that can switch the DC to turn the elements on and off.  You can get a 
variety of 120 volt and 240 volt elements at anywhere from 500 to 4500 
watts.  If you use a 240 volt element at a lower voltage, remember every 
time you cut the voltage in 1/2, the wattage drops by 75%.
The same should be true for resistance wiring in a slab. The benefit of 
heating water is that you have more control of  the slab heat. You can 
pump the stored hot water through the slab when you need it.
David

David Katz
President, AEE Solar
formerly Alternative Energy Engineering
1155 Redway Drive - Box 339
Redway, CA 95560 USA
Phone (707) 825-1200
Fax (707) 825-1202
email: david at aeesolar.com
web: www.aeesolar.com


Geoff Greenfield wrote:

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>Happy holidays all you listers...
>
>I have been presented with an interesting customer design I want to
>improve...
>
>They have an S-load of wind (15 m/s... about 7kw most of the time) and are
>looking at a Bergey 7.5 48 volt unit with a pair of VFX3648s and a string of
>L-16s.  Very few AC loads - mostly they plan on powering an electric hot
>water tank that will serve a radiant floor system (all yet to be built).
>
>So - doesn't it mak a lot more sense to A) heat the water with DC elements
>eliminating the conversion loss and or B) heat the slab directly with some
>sort of DC resistance wire....
>
>And if B, then C - where and what (I have seen AC floor heating grids - any
>source for DC?)
>
>The entire concept of "heating" with renewable energy (other than passive
>solar) is so foreign to me that my brain locks up just going there.  BTW -
>this is a birth center/health clinic in Bolivia.  Already planning on a
>voltage relay to take out the heat circuit at low voltage.
>
>For a brighter energy future,
>
>Geoff Greenfield
>NABCEP Certified Energy Practitioner
>
>THIRD SUN SOLAR & WIND POWER Ltd.
>340 West State Street
>Athens, OH 45701
>
>www.third-sun.com
>(740) 597-3111
>
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