Solar Space Heating Storage Tank Size [RE-wrenches]

[Tom Lane, Energy Conservation Services]

oops OOPS CORRECTION   3 square feet of collector area requires 1 foot of
finned 3/4" copper tubing OR 1 sq. ft. of collector area to 1 foot of smooth
3/4" pipe or 1.5' of smooth 1/2" pipe. (This is considered the minimum
requirement for transferring heat from the collectors through immersed coils
into storage. If you are using drainback systems which are the best systems
for space heating if your water or water/glycol mixture is draining back
into an unpressurized reservoir AND you are pulling heat out of the
reservoir for distribution, the golden rule is to cram as much copper into
the reservoir  as feasible regarding storage.  The salient point is not to
exceed 3 gallons per sq. ft. of collector area or you will have no benefit
from the increased storage.  Important point: On an unpressurized reservoir
it is important that the return from the collectors be introduced at least a
foot below the water level.  All suction to the collectors should be pulled
from the bottom out the top with no penetrations below the water level.  If
you are running distribution through the copper coils and the reservoir, try
to feed at the bottom of the coil and return out of the top.

GATOR TOM

 ----- Original Message ----- 
From: "Travis Creswell, Ozark Solar" <ozsolar at ipa.net>
To: <RE-wrenches at topica.com>
Sent: Tuesday, March 09, 2004 6:33 PM
Subject: RE: Solar Space Heating Storage Tank Size [RE-wrenches]


> Thanks for the rules of thumb.  3 to 4 lineal feet copper per sq ft of
> collector?  Wow!  That's 328 ft2 (1600 lineal) of copper coil for my 400
ft2
> of collectors.  That would surely do it!  Did you mean 1 lineal foot of
> copper pipe per 3 to 4 sq. ft of collector?  That would be more in line
with
> my rule of thumb.
>
> The easiest way I've found to make heat exchangers out of soft copper it
to
> use a 100 lb propane cylinder (full of propane, of course!).  1) Uncoil
the
> copper down a small incline in the yard.  2) Start at the top of the hill
> and wrap the coil around the propane cylinder as you roll it down the
hill.
> The cylinder is the perfect diameter. It's heavy so it easily and smoothly
> coils the copper and when you're done the coil slips right off!
>
> Best,
>
> Travis Creswell
> Ozark Energy Services, Inc.
>
>
> -----Original Message-----
> From: Tom Lane, Energy Conservation Services [mailto:tom at ecs-solar.com]
> Sent: Tuesday, March 09, 2004 9:27 AM
> To: RE-wrenches at topica.com
> Subject: Re: Solar Space Heating Storage Tank Size [RE-wrenches]
>
> Rules of Thumb:
> *    When you exceed 3 gallons per sq. ft. of collector area you get no
> benefit from additional storage.  Typically 1.75 to 2.5 gallons per sq.
ft.
> is the best ratio of gallons per sq. ft. if you are also space heating
> during the day.
> *    Make sure all penetrations are above the water level.
> *    Get 30 or 50 gallon metal drums and roll form 3/4" copper type L pipe
> around the drums to form a coil. Use 3 to 4 lineal feet of 3/4" copper per
> sq. ft. of collector area.  Use bare copper ground wire to wire the spread
> coil to a copper ground road. Pull your heat from the bottom coils to the
> top.  You can buy finned coils from SEPCO, VAUGHN, or WOLVERINE COPPER -
but
> it is more cost effective to make your own.
>
> Gator Tom
>
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