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Using old electric water heater as tempering tank?

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Using old electric water heater as tempering tank? Steve 03-12-2008
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Posted by Steve on March 12, 2008, 6:15 pm
On Mar 12, 4:54=A0pm, nicksans...@ece.villanova.edu wrote:
> Sounds good to me. An alternative is 3 or 4 10'x4" PVC pipes tucked up und=
er
> the joists, if they are exposed. You might use close nipples and rubber
> washers as bulkhead fittings between them, with garden hose adapters
> at the main inlet and outlet, like this, viewed in a fixed font:
>
> =A0---------------------------------------------------
> |in =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =
=A0 =A0 =A0 =A0 =A0 =A0out|
> =A0---------------------------------------------------
> =A0---------------------------------------------------
> |out =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =
=A0 =A0 =A0 =A0 =A0 =A0in|
> =A0---------------------------------------------------
> =A0---------------------------------------------------
> |in =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =
=A0 =A0 =A0 =A0 =A0 =A0out|
> =A0---------------------------------------------------
> =A0---------------------------------------------------
> |out =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =
=A0 =A0 =A0 =A0 =A0 =A0in|
> =A0---------------------------------------------------
>
> The main outlet could connect to the water heater drain.
>
> The pipes would hold about 220 pounds (26 gallons) of water with 40 ft^2
> of surface. In slow-moving air with a 1.5 Btu/h-F film conductance,
> RC =3D 220/(40x1.5) =3D 3.7 hours. After 4 hours in 100 F air, water
> would warm from 55 to 100+(55-100)e^(-4h/3.7h) =3D 85 F. A foil
> wrap around the pipes and insulation above them would help.
>
> Nick

Thanks! That sounds like a good plan also. But my ceiling joists are
pretty full or covered with ductwork and stuff. Especially over my
wood stove which would be the best place for something like this. And
I wonder about a dripping of condensate problem in the summer?? With
my wood stove going strong in the winter months, my basement near the
wood stove is easilly close to 90 - 100 degrees F and I don't think it
would make me have to burn any more wood because of it if I put my old
hot water heater tank (which is fiberglass vintage 1978) close to the
wood stove. Do you think it would cause a loss of or problem with
water pressure? I have a well system with 35 - 45 psi.
Thanks again!
Steve

AppliancePartsPros.com, Inc.
Posted by ransley on March 12, 2008, 7:41 pm
> On Mar 12, 4:54=A0pm, nicksans...@ece.villanova.edu wrote:
>
>
>
>
>
> > Sounds good to me. An alternative is 3 or 4 10'x4" PVC pipes tucked up u=
nder
> > the joists, if they are exposed. You might use close nipples and rubber
> > washers as bulkhead fittings between them, with garden hose adapters
> > at the main inlet and outlet, like this, viewed in a fixed font:
>
> > =A0---------------------------------------------------
> > |in =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =
=A0 =A0 =A0 =A0 =A0 =A0out|
> > =A0---------------------------------------------------
> > =A0---------------------------------------------------
> > |out =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0=
=A0 =A0 =A0 =A0 =A0 =A0in|
> > =A0---------------------------------------------------
> > =A0---------------------------------------------------
> > |in =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =
=A0 =A0 =A0 =A0 =A0 =A0out|
> > =A0---------------------------------------------------
> > =A0---------------------------------------------------
> > |out =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0=
=A0 =A0 =A0 =A0 =A0 =A0in|
> > =A0---------------------------------------------------
>
> > The main outlet could connect to the water heater drain.
>
> > The pipes would hold about 220 pounds (26 gallons) of water with 40 ft^2=

> > of surface. In slow-moving air with a 1.5 Btu/h-F film conductance,
> > RC =3D 220/(40x1.5) =3D 3.7 hours. After 4 hours in 100 F air, water
> > would warm from 55 to 100+(55-100)e^(-4h/3.7h) =3D 85 F. A foil
> > wrap around the pipes and insulation above them would help.
>
> > Nick
>
> Thanks! =A0That sounds like a good plan also. =A0But my ceiling joists are=

> pretty full or covered with ductwork and stuff. =A0Especially over my
> wood stove which would be the best place for something like this. =A0And
> I wonder about a dripping of condensate problem in the summer?? =A0With
> my wood stove going strong in the winter months, my basement near the
> wood stove is easilly close to 90 - 100 degrees F and I don't think it
> would make me have to burn any more wood because of it if I put my old
> hot water heater tank (which is fiberglass vintage 1978) close to the
> wood stove. =A0Do you think it would cause a loss of or problem with
> water pressure? =A0I have a well system with 35 - 45 psi.
> Thanks again!
> Steve- Hide quoted text -
>
> - Show quoted text -

In summer heat is free, as in the water will come in at 50f and heat
free to 70f, a big savings, PVC wont transfer heat like Copper, Copper
will absorbe summer heat more efficiently Do it but Copper is best.

Posted by Steve on March 12, 2008, 10:32 pm
> In summer heat is free, as in the water will come in at 50f and heat
> free to 70f, a big savings, PVC wont transfer heat like Copper, Copper
> will absorbe summer heat more efficiently =A0Do it but Copper is best

Thanks! I think I will do this. My plumbing is mostly copper already
so I plan to stay with it. If I can save up to 5 kwh/day (about 30%
less on time) with this @ .10 / kwh, it could be a savings of up to
$180 / year. Enough to payback the new heater!
Steve

Posted by on March 13, 2008, 9:24 am

>In summer heat is free, as in the water will come in at 50f and heat
>free to 70f

Not in the basement :-)

>PVC wont transfer heat like Copper, Copper will absorbe summer heat more
>efficiently Do it but Copper is best.

No, given the much larger limiting airfilm resistance.

Nick


Posted by on March 13, 2008, 9:15 am

>> ... An alternative is 3 or 4 10'x4" PVC pipes tucked up under the joists

>... my ceiling joists are pretty full or covered with ductwork and stuff.
>Especially over my wood stove which would be the best place for something
>like this.

Warm air rises, so the pipes might work well anywhere in the ceiling.
I removed most of the wooden cross blocking in the basement ceiling of
my neighbor's house and tucked 60 50-pound capped 4"x10" thinwall PVC
pipes between the joists with 1x3s beneath to add 3K Btu/F to the house
thermal mass and make the basement woodstove heat last longer. A few
more thickwall pipes to make a tempering tank would be useful.

>And I wonder about a dripping of condensate problem in the summer??

You might catch any condensation with a piece of plastic stapled beneath.
If it happens a lot, the basement may need airsealing or dehumidification.

Nick


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