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Looking for heat exchanger tank

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Posted by carneyke on March 15, 2006, 2:55 pm
Hello All,
I am looking for a storage tank and have found several on-line in the
60 - 90 gallon range. Problem is they have built in electric heating
element that I don't need and they cost anywhere from $00 to $000 US.
Does anyone have any idea for a plain jane insulated heat exchanger
tank ?  Thanks, Kevin

Posted by Gary on March 15, 2006, 4:26 pm
carneyke wrote:

Hi Kevin,

Here are some potential schemes:

1) I have seen schemes where you use a conventional hot water tank, take the
insulation off it, wrap a coil of soft copper pipe around the out side of the
tank, do something to provide a good thermal connection between the tank and the
coil, and put the insulation back on.  The "do something to provide a good
thermal connection" is the tricky part.
It does (effectively) result in a double wall heat exchanger, which is good.

2) This Butler wand heat exchanger fits into a normal hot water tank, and is
less expensive than one of the storage tanks with a heat exchanger built it.  It
is not as efficient as a conventional heat exchanger, but the simplicity of it
might be worth the sacrifice. More info on it here:
(under "Solar Wand")

3) If the tank does not need to be pressurized, then the Home Power article
article listed below shows a very inexpensive way to combine a heat exchanger,
drain back tank, and storage tank into one $0 poly barrel.  Seems like a pretty
nice idea to me.

At the risk of getting into trouble with Home Power, here is a bit of text
excerpted from the article -- for a small fee, you can download issue 88 from
the Home Power website ( www.HomePower.com ).

Excerpt from "Solar Hot Water, Homebrew Style", issue 88:
Drainback Reservoir & Heat Exchanger
The drainback reservoir is also the solar storage tank.
Jay used a recycled, 50 gallon (190 l), plastic olive
barrel with lid. Water held in the reservoir tank is
circulated through the collectors. Domestic water
circulates through a copper coil heat exchanger
submerged within the reservoir tank.
The heat exchanger consists of a 50 foot (15 m) coil of
1/2 inch, soft (type L) copper tubing. This is adequate for
Jay's modest hot water use. Larger households would
benefit from a greater heat exchange capacity in order
to heat water in a single pass. Type L soft copper is
purchased in coils and can be easily bent into gentle
sweeping curves or coils. Type M is rigid copper pipe,
which comes in 20 foot (6 m) straight lengths and is
used for most plumbing runs. Both types of copper pipe
are readily available at local plumbing supply houses.
As domestic hot water is used, the cold inlet water
passes through the heat exchanger, where it picks up
solar heat by conduction through the wall of the heat
exchanger pipe. The 50 gallon (190 l) reservoir tank is
90 percent full when the system is at rest. When the
pump is circulating water through the collectors, the
water level drops to approximately 85 percent full.
This approach is a bit different from most drainback
solar hot water systems. Three tanks are commonly
used: a reservoir tank, a solar storage tank, and a
backup water heater tank. The more typical 10 to 20
gallon (3876 l) reservoir tank simply holds the water
that drains back from the collectors when the circulating



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Posted by carneyke on March 15, 2006, 5:38 pm
Thanks for the information.

Posted by Jeff on May 15, 2006, 5:20 am

Here's the way I picture this.

The drain from the collectors feeds the top of the storage tank.

   The DMH coil starts at the bottom and finishes at the top where the
water is hotter. Or should we ignore stratification?

What makes copper tubing refrigeration tubing? Is that bad?


Posted by nicksanspam on May 15, 2006, 12:41 pm

Thiner walls, which may not last long in water.


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