Digest for RE-wrenches at topica.com, issue 1936 [RE-wrenches]

Fri Nov 25 10:37:35 PST 2005

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-----Original Message-----
From: RE-wrenches at topica.com
Date: Fri, 25 Nov 2005 04:16:29 
To:RE-wrenches at topica.com
Subject: Digest for RE-wrenches at topica.com, issue 1936

-- Topica Digest --

	Re: DC heat
	By conradg at cape.com

	Re: DC heat
	By ken at commonwealthsolar.com

------------------------------------------------------------

Date: Thu, 24 Nov 2005 08:47:17 -0500
From: conradg at cape.com
Subject: Re: DC heat [RE-wrenches]

Does anybody have any experience/recommendations for residential size 
groundwater heat tranfer heat pumps?
Conrad
Cotuit Solar

On Tue, 22 Nov 2005 08:02:34 -0800, Todd Cory, Mt. Shasta Energy Services 
wrote
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> 
> It is a common misconception that heat pumps do not work well at low 
> temperatures. Our air source, split (no ducts), mulit zone system 
> still performs at over 200% efficiency at 10 to 15 degrees F. Our 
> 30K btu unit has a 2 pole 30 breaker and "only" draws around 2500 
> watts running full out. The defrost cycle happens depending on the 
> outside temperature and humidity.
> 
> I love it and it has made our home zero energy with 3.2 kWh of PV.
> 
> Todd
> 
> Geoff Greenfield wrote:
> 
> >Thanks for all the input-
> >
> >I could suggest heat pump to the customer, however - one of the design 
goals
> >is simplicity (this is a remote installation in the high plateaus of 
Bolivia
> >after all).  There is no allowance for duct work in this building, and the
> >goal was to minimize battery plant, inverters and BOS... Also - my 
(minimal)
> >understanding of Heat pumps (air source) is that at about 20 degrees they
> >turn on the resistance strips anyway.... and sometimes there is a defrost
> >cycle etc...  I always tell battery based folks to not try and power them
> >(the last one had a 100 amp 240 breaker).  In response to Ian's thoughtful
> >post I need to learn more and open my mind to such possibilities.  I am
> >going to add a couple window AC units to MY house next summer....
> >
> >In a sense, DC resistance heating from the wind is kind of like direct 
water
> >pumping.  In my scheme we heat the slab directly (after charging our 
minimal
> >battery bank saved for AC loads).  Perhaps even go with two layers of heat
> >and heat the deeper layer after a T-stat is satisfied.   According to David
> >Katz - we can use off the shelf AC stuff with DC - this seems simple.
> >(Hmmm... how about 3-phase wild AC?)  Resistance heat is inefficient, but
> >also simple, reliable, easily installed and transported, avoids battery 
wear
> >and tear and battery/inverter losses.  This is where my gut is leading me -
> >any objections?
> >
> >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
> >
> >Your free subscription is suppo
> >
> 
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------------------------------

Date: Fri, 25 Nov 2005 06:50:06 -0500
From: "Ken Schaal" <ken at commonwealthsolar.com>
Subject: Re: DC heat [RE-wrenches]

Regarding the comments below---

I have used Florida Heat Pumps for years. They have both air and water
output. Which brand to use probably depends on your local distributor.

In 1986 we used an early Sanyo split system air source --9000 btu-- to heat
and cool our prototype geodesic dome offices. Even after being encased in
ice one particularly bad ice storm, it worked well. No strip backup !

Ken at Common Wealth Solar

-------Does anybody have any experience/recommendations for residential size
groundwater heat tranfer heat pumps?
Conrad
Cotuit Solar

>
--------> It is a common misconception that heat pumps do not work well at
low
> temperatures. Our air source, split (no ducts), mulit zone system
> still performs at over 200% efficiency at 10 to 15 degrees F. Our
> 30K btu unit has a 2 pole 30 breaker and "only" draws around 2500
> watts running full out. The defrost cycle happens depending on the
> outside temperature and humidity.
>
> I love it and it has made our home zero energy with 3.2 kWh of PV.
>
> Todd
>

------------------------------

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End of RE-wrenches at topica.com digest, issue 1936

Jeremy Page
New Vision Technologies
(949) 218-0235

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