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Posted by Lawrence on March 28, 2008, 10:17 am
> As you may know, an electric water heater can be 30% of your electric
> bill...
>
> Well I got to thinking... I have this nice woodstove which puts out a lot =
of
> heat and it is always 80 to 100 degrees (F) next to the woodstove.
>
> Is there some way I can use this heat to "pre-heat" the water going into m=
y
> hot water heater????
>
> Well I came up with an idea and tried it out. It works!
>
> I got a used 50 gallon water heater at a recycling center. Then removed th=
e
> sheet metal cover and removed the insulation. So now I had just a bare met=
al
> 50 gallon tank. I painted it black as in theory black absorbs heat better.=
>
> Then I placed this tank next to my woodstove. Then disconnected the cold
> water going to my hot water heater and ran that to the bottom (drain)
> connection on the tank by the woodstove. Then ran a pipe going out the top=
> of the tank by the woodstove to the cold water inlet of my electric hot
> water heater. (Cold into the bottom, warm out the top.)
>
> Note: My electric water heater is located on the other side of the wall ne=
xt
> to my woodstove.
>
> After just a few hours, the water coming out of the top of the tank by the=
> wood stove was about 70 degrees. (The water from the city going into the
> tank is 40 degrees F.) At this point the bottom of the tank felt cold and
> the top was not cold.
>
> The next morning, the entire tank was slightly warm.
>
> Anyway I am now "pre-heating" the water going to my hot water heater. So
> instead of my water heater having to heat up 40 degree water, it will only=
> need to heat up water which will be from 70-80 degrees. Perhaps warmer if =
I
> have the woodstove going full blast and have not used any hot water for a
> while. So should save some $$ on my electric bill.
>
> Building code note: Now that I see this idea works, I'm going to install t=
he
> tank next to my woodstove to "code"* like a water heater tank would be. Th=
at
> is drip pan, T&P valve, and strapped to wall for earthquakes. *I don't
> suppose code covers anything like this? I also installed a valve and pipe =
to
> outside for draining the tank.
>
> Temperature and "steam" note: The temperature next to my woodstove never
> gets above 115 degrees F. and water boils at 212 degrees. So no possibilit=
y
> of steam being created.
that sound like its working and and I see no question here. One
application that I have seen is to use a wood boiler to heat all of
your hot water with a heat exchanger. It can also be used to heat the
entire house in several different ways.
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