SHW with dual-coil tanks [RE-wrenches]

[Tom Lane]

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The water side pump is usually a one fortieth to one hundred 
horsepower --insignicant to the 20% increase in  BTU,S collected  gatortom
----- Original Message ----- 
From: "Ray Walters" <walters at taosnet.com>
To: <RE-wrenches at topica.com>
Sent: Wednesday, June 18, 2008 12:17 PM
Subject: Re: SHW with dual-coil tanks [RE-wrenches]


>
>
> Also don't forget you're trading electrical efficiency (to run the  extra 
> pumps) for thermal efficiency. We've had cases where customers  added both 
> solar thermal and PV systems at the same time, and the  thermal system ate 
> most of the PV production.
>
> Ray Walters
>
>
> On Jun 18, 2008, at 8:23 AM, Blair May wrote:
>
>>
>> Simple physics true, but what about the service life of the ExHEx when
>> in use w/ hard water, compared to internal HEx coils?
>>
>> -----Original Message-----
>> From: Tom Lane [mailto:tom at ecs-solar.com]
>> Sent: Tuesday, June 17, 2008 9:02 AM
>> To: RE-wrenches at topica.com
>> Subject: Re: SHW with dual-coil tanks [RE-wrenches]
>>
>>
>>
>> All dual pumped EXTERNAL HEAT EXCHANGE SYSTEMS WHERE THE approach
>> temperature IS PROPERLY SIZED   will outperform all  HEAT EXCHANGE  TANKS
>>
>> THAT RELY  on convection by 20% with the same collector area --simple
>> physics.  gatortom
>> ----- Original Message -----
>> From: "Doug Wells" <dwells at thesolarspecialists.com>
>> To: <RE-wrenches at topica.com>
>> Sent: Monday, June 16, 2008 1:02 PM
>> Subject: Re: SHW with dual-coil tanks [RE-wrenches]
>>
>>
>>>
>>> Nik,
>>>
>>> I am uncertain about the move to dual coil tanks in the NorthEast. I
>>> doesn't make sense to me.  Besides the fact that much of the work is
>>> retro-fits. Anyway, by keeping the 2 tank system you are keeping a
>>> much higher efficiency during the darker colder months.
>>> By having a large body of cold water to dump heat into every time
>> there
>>> is sun, you are keeping efficiencies way higher.
>>> The solar can heat say 80 gallons of water to a temperature of 110 on
>> a
>>> sunny winter day.  This can vary greatly, but stay with me.
>>> Heating the incoming water from 50 to 110 degrees is a significant
>> amount
>>> of heating.  The goal is to have as many of the Btu's coming from
>>> the sun as possible.  Then the primary tank takes the water up to 120
>> or
>>> 150 or whatever they have the tank set at.  Still a large reduction
>> in
>>> the heating
>>> of the primary tank.
>>> Having a single tank does save money, but how much?  $1-2,000?  With
>> the
>>> current cost of fuels it seems that 30 years of partial winter
>> heating
>>> will
>>> pay for itself.
>>> The single tank system works in theory, but the stratification of the
>>> tank is not absolute.  It depends on demand, usage patterns and tank
>>> temperature.
>>> As always, we need more concrete numbers on the temp. stat. in a
>> single
>>> tank.  I am reluctant to give away an awful lot of partly  cloudy  days
>> up
>>> here that
>>> could heat a second tank, but might not be able to over come a single
>>> tank with boiler coil.
>>> I might try a single tank system in a new application with an
>> intelligent
>>> control system,
>>> but I am sticking with 2 tanks for most work.
>>> Thoughts?
>>>
>>> Doug Wells
>>> The Solar Specialists
>>> Worcester, VT 05682
>>> (p) 802-223-7014
>>> (c) 802-498-5856
>>> www.thesolarspecialists.com
>>>
>>>
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>>>
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>>>
>>
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>>
>
> R. Walters
> Solarray.com
> NABCEP # 04170442
>
>
>
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