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re: my fridge...my water heater
3 oct 2001
peterthinks wrote:
>i was thinking of gutting an old fridge for it's condensor coil (big coil
>on back) and running the cold water that fills my hot water tank thru it.
seems like a good idea. why not use a working fridge? my ge tbx18... has
a 6"x6" fin-tube radiator underneath with a 6" fan. it was 89 f in a 66 f
room when the fan was running. it might supply (89-55)/(115-55), ie 57%
of the energy needed to heat water from 55 to 115 f, or a more, if the
radiator runs hotter and the fridge runs less-efficiently. the fridge
would consume less power without that fan...
the label inside the fridge says 115 v at 6.5 a, ie about 748 watts, so
it could move 2243 watts of heat with a cop of 3, ie 7651 btu/h, enough
to heat 225 pounds or 28 gallons of water from 55 to 89 in 1 hour, ie
a significant fraction of a household's water heating needs. maybe all
of their needs, if they use 89 f water, as people do in the caribbean.
>i'd strap the water coil to my running fridge's condensor coil...
how would you do that, exactly? if the cold water only moves through the
heating coil once on the way to the water heater, and it only moves when
hot water is being used, this won't be a very efficient heat exchanger,
even if the "straps" are good thermal conductors.
seems better to somehow immerse the original radiator in a liquid, eg oil,
and let heat thermosyphon up through another heat exchanger inside a
pressurized tempering tank in series with a point-of-use heater, keeping
the hot water lines short to minimize cost and heat loss, and helping
the point of use heater achieve higher throughput. sounds complicated.
does anyone make a suitable inexpensive heat exchanger that could replace
the original radiator, with pressurized water on one side and freon on
the other? could we make one with a couple of pieces of different diameter
copper pipes and ts?
a 6-10 gallon tank might be enough to cover a typical hot water use.
the tank might have a thermostat that turns on a fan to move room air
through the fridge compartment when the tank temp is less than 85 f...
nick
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