Ok guys, pick this one apart..... I have a wood stove in my
basement. I just replaced my old 52 gal electric hot water tank with
a new 40 gal model. I am planning to use my old stripped down tank as
a tempering tank ahead of my new heater and place it as close to my
wood stove as possible (about 6 inches or so away). I plan to remove
the upper and lower elements on the old tank and replace them with a
1" copper line from the top element threaded opening to the bottom
threaded opening and extend the copper line over my wood stove so that
it will pick up heat from the stove / flue pipe. I am thinking cool
water from the bottom will naturally be drawn up the copper line as it
is being heated by the wood stove and will circulate back to the top
and will constantly be looping around to warm the water inside the
tempering tank. I am thinking that possibly overnight, the water in
the tank will eventually warm up to around 100 degrees F. And the new
electric heater will only need to heat that water up to 120 degrees
F. There are only two people in the house and no automatic
dishwasher, warm water usage for the wash cycle only of the clothes
washer @ 2 loads per week, and maybe two short showers per day. Do
you think this is a feasable plan? I am not any kind of engineer, but
just a practical tinkerer trying to save a few bucks on my electrical
bill......... Thanks for any comments on this!
its a interesting idea, but i doubt large gains:( I woul;d of stuck
with the larger tank since its a long life purchase and more gallons
cost little more.
plus to be effective you will have to constantly be turning the
electric water heater off and on, or gain very little
I kept a tank that was not leaking and use it as a tempering tank from
air temp, just that alone saves a bit, just a tank next to a heat
source will help alot, try it and figure out and put in bypass valves
so when something leaks you still have HW. My electric 40gal tank cost
about 35 a month to run, my present NG Tankless costs $9 in summer
with all gas cooking and clothes dryer and using the electric as a
tempering tank might be saving me a few $ a month. Be inventive all
Thanks for the comments! I plan to have shut off valves so I can
always go back to the standard setup. I do plan to go back to the
standard setup for summer as there will be no heat from the woodstove
at that time anyway. I guess I thought the 40 gal capacity for the
new heater would be sufficient for two people in the house and it was
about $30 less to buy than the 50 gal model. To begin with, I don't
plan to be shutting the new electric one off and on. It is well
insulated and has heat sinks in the inlet and outlet so it should not
be cycling on too much during the night. It's probably going to be
alot of work and probably about $40 to $50 for materials to get it set
up and probably at best it might save $15 a month during the heating
season (6 to 7 months in our area) so about $100 / year possibly? At
least I don't have to pay anybody to do the installation work.
think about what you said, other than passive gain from the tank the
recirle line will be a loser.
tempered but still cold water enters, heater turns on, water gets to
120 and heater shuts off.
now some water recirls from the heat loop. if its not at least 120 it
will be cooling your tank and costing more money for electric.
as to tankless, electric tankless capable of running a home will
likely take 200 amps just to heat water. even ifd its just a 100 you
would still need a main service upgrade 200 amps for home, 200 amps
for heating water.......
new lines service power drop:( not worth the cost
Like I said I am not an engineer and can't do the thermodynamic
equations and btu loss or gain or heat transfer calculations. All I
can do is try it and see what happens. You could be right about the
heat loop not working out.... But its not quite like going to the
moon and not coming back is it (rocket science)? But seriously, I do
appreciate your comments as I am willing to learn and appreciate
All comments are very welcome and appreciated!
The proposed recirculation line originates and terminates at the
tempering tank. So no water from the electric water heater tank is
displaced from the recirculation line. The recirc line is just a way
to increase the heat gain of the tempering tank from the wood stove.
Even if its 70 from the stove it will be a winner, his incomming will
be likely 55 or less in winter, mine goes to 35-36f, if basement air
is above water temp he wins. Above a stove will be maybe 300f, and
tank is also next to wood stove.
Go ahead and use the tempering rtank in the summer. You'll at least
bring the water temp up from ground temp, which could be ~55F or so to
air temp, which could be ~70F or however hot it gets in the
Your new 40-gallon tank will be more than sufficient for the two of
you plus any guests you might have. We have a 40-gallon gas Bradford
White water heater for our 2,500 sf house (full bsmt, 1st, 2nd, and
3rd floors), and we've not had any water shortages even with as many
as 7 people in the house, and we use a dishwasher plus washing
machine. Obviously all the hot water demand can't be in the same
moment, so we just make sure to run the dishwasher and washer at times
when people are not likely to be showering, and all is good.
i'm thinking this will work fine. BUT i wonder why you are retiring the
tank if it is still sound enough to be a tempering tank? I doubt if you get
the water to 100, but it'll be a damn site warmer than the incoming water.
Good question! One of the thermostats went out on my old heater. It
was 30 + years old and I figured it was as good of a time as any to
try this tempering tank idea which I have been thinking of trying for
a long time. It just might be a dissapointment but I am willing to
I didn't read all the details in the original message, but have you considered
the total energy flows?
If the tempering tank is inside the building thermal envelope, the energy needed
to bring the water up to room temperature has to come from somewhere - most
likely your space heater. So, it isn't free.
If the tempering tank is outdoors, you have to consider that you have an
unheated space that will be chilling the water for at least part of the year...
What hotel, the only hotel I heard of it was in stagnant water from AC
chillers or other AC equipment. I can understand non chlorinated, warm
pooled water growing anything, but chlorinated, sealed, moving,
pressurised systems, no I have not heard that as fact.
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