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Plumbing a Solar DHW System

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Posted by kickaha on July 21, 2005, 8:20 pm
 
Hi, all-

I have a solar DHW system at my house and I'm curious about how it is
plumbed: I have an 80 gallon storage tank plumbed to my collector loop
and this tank feeds my electric (!) water heater that supplies the
house.

I'm wondering why the electric water heater isn't plumbed into the
collector loop.

It seems to me that the water in the electric water heater will tend to
cool off in the daytime and have to be heated electrically when the
evening rolls around.

Wouldn't it be better to have the electric water heater plumbed into
the collector loop? Or will the tank not cool off enough to make a
difference?

kickaha


Posted by Gary on July 22, 2005, 12:38 am
 
kickaha@workmail.com wrote:

This is the normal way of plumbing a solar hot water system.  The
solar storage tank allows for storing a supply of hot water during
sunny periods.  As long as the water coming from the storage tank is
hot enough, the element in your electric tank won't turn on.  The drop
in temperature of the water sitting in the electric tank is small as
long as the tank is reasonably well insulated.
During the summer (when the solar system can provide all the hot
water), some people turn off the electric hot water heater, or bypass
the electric tank.  During the winter the electric tank will probably
be needed for those times when there is not enough sun to fully heat
the water.  Even if the solar heater can't heat the water all the way,
you are still getting benefit from your solar heater, and the separate
solar storage tank allows the collectors to heat the water as much as
they can.

If you go to this link at HomePower Magazine, there are free downloads
of a couple good articles on the basics of how the closed loop solar
water heating systems work, and why the components are hooked up the
way they are -- I'd try the articles in issues 84 and 85.

http://www.homepower.com/magazine/downloads_solar_thermal.cfm

More stuff on solar water heating at my site:
http://www.builditsolar.com/Projects/WaterHeating/water_heating.htm



Gary

www.BuildItSolar.com
gary@BuildItSolar.com
"Build It Yourself" Solar Projects









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