wrote:
I'm still thinking about heating water with 1/3 the usual energy using a Haier
5K Btu/h window AC ($84 at Wal-Mart.) The pipes connect to the condenser coil
at the top, so we could build a thin aquarium around it with no replumbing or
recharging and pump 1.5 gpm of 110 F water out through a $168 Doucette SB1-20
400 Btu/h-F plate heat exchanger with a 110 F thermostat and pump 60 F cold

This is actually not crazy at all.

5500btus for 550watts of power is an excellent return on your power
that's 10btus per watt (ie EER 10). 3.41btus per watt of electricity
means that if you used 550 watts for straight heating you would only
yield 1875 btus (that's an EER of 3.4). If you couple that with
getting cooling on one side and heat in your water you could have even
more savings.

Here is support of this idea:

1. Commercial pool heaters come in an electric heat exchanger version
(which is simply a reverse A/C. On warm days they are actually more
efficient then oil or gas since it's a heat exchanger and not simply
gaining all it's energy from the fuel source.

2. My brother purchased a unit a while back (they come up on ebay
every once and a while) which is a made from scratch version of this
that mounts in his house that gives him 5000 btu's of cooling and on
the condenser has a water loop that circulates into his hot water
heater. I don't think they make it anymore it was the WH6BX and made
for the house. Take a look at:

http://www.aers.com/specsheets.html
Look at the spec sheet for the: R106K-5

This is a little more industrial, but is the same conceptually.

3. I took a window a/c unit a while back to heat a small swimming pool
(kids pool 1500 gallons). I literally built a plexyglass box around
the condenser inside the unit with the top off. That way I didn't have
to break the refrigerant line since I have no idea how to charge them.
I removed the fan blade, but left the motor shaft untouched. I then
ran a small pond pump from the swimming pool through the condenser.
Overall it worked. Measurements on input temperature vs output
temperature and flow rate showed over 90% reclamation of the heat. The
A/C side sending out cold air. However the big problem was I held the
entire plexyglass enclosure together with RTV and I had multiple leaks.
In the end I went with a solar cover. If you choose to do this, low
pressure is the only way to do it unless you cut your condenser out of
the unit and encase it in something else. Maybe encasing it with metal
would have worked better but soldering around the condenser may not be
safe.

Good luck. I might be able to dig up a photo. Email me if you are
interested.

One little additional comment, heat exchangers only work well in warm
weather. In the North you don't see them on homes, because when it's
10 degrees out it's not efficient to extract energy from the air.

lowtech87501