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
water into the other side of the heat exchanger from a cold kitchen tap and
back into the hot tap, and dump some hot water from the hot tap into the sink
with a solenoid valve if the cold tap ever reaches say, 100 F, when/if the
tank water heater completely fills. Heating 50 gallons of 60 F water to 110
takes about 21K Btu, and the AC would make about 5000(1+1/3) = 6700 Btu/h,
so we might fill the tank in 3 hours, with no hot water use.
When I blocked the Haier AC condenser airflow to make the exit temp 110 F,
its cool air temp and power use (from a Kill-a-Watt) barely changed.
This could be more efficient than a typical "portable air conditioner" with
air hoses. Removing the condenser fan blade might also raise the COP.
about hooking hoses up to the spouts of the kitchen sink taps, but to
the pipes feeding them.
About 40 years a go one of my friends had a water cooled central air
system in his Massachusetts home. All the equipment was in the basement
furnace room. The cooling water went down the drain most of the time,
but he did have a valving setup which allowed him to water his lawn with
that warm water if he wanted to.
Googling "heat pump water heater" got over 49,000 hits, and it looks
like it's proven technology:
Hmm, I wonder if Mr. Milligan even knows this technology exists? If he
does, I wonder why he felt the necessity to hurl an insult at you.
(Rhetorical question, see my sig line.)
There are places that do almost that. The very first shopping center
in the world was in Minneapolis. They stored the heat from the summer
in a natural underground pool of water. Then they used that heat during
the winter to heat the building. They didn't need all the heat that ws
stored so it got to where they had to do additional cooling during the
As for using an AC to heat water. Why? If you need air conditioning
there is more than adequate solar heat for water. Heating water will
only degrade the operation of the refrigerant. And the water will not
be warm enough for any practical use. We already have problems with a
surplus of warm water. Nuclear Power plants for example.
If water is used for cooling a large supply of cold water is needed.
A building in the San Fernando Valley used a large pool with fountains
to cool their refrigerant. The water started to get too warm so they
raised the nozzles on the fountains a couple feet to get more
evaporation and cooling.
Nick, can you explain a little more here. Are you saying pump from a hot
water tank the cooler water at the bottom through plate heat exchanger and
into the top of the hot water tank? A loop through the hot water tank?
Funny you should mention that, my first job out of grad school circa '58
was with a commercial R&D company, Comstock & Westcott in Cambridge,
Mass. They had developed right before WWII (and I think patented it
too.) a gas powered refrigerator with a domestic hot water storage tank
built on top of it. They trade named it "Stator". The water in the tank
received the heat pumped out of the refrigerator.
The war years interfered with producing and marketing it, and during the
fat times after the war nobody gave a damn about saving energy, plus the
darn thing was about 8-1/2 feet tall and wouldn't fit in the post war
houses with their lower ceilings.
There were a couple of those units standing around in the company shop
when I started working there, but as far as I know no more were ever built.
Thanks for the mammaries...
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
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:
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
Good luck. I might be able to dig up a photo. Email me if you are
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.
Hi folks. I work for AERS, Inc. which was sited earlier in this
thread. They have successful heat pump water heating installations
numbering in the tens of thousands-- residential, commercial and
industrial. For the R106K, 1/3rd of the heat generated by this unit is
purchased electricity. The other 2/3rds comes from renewable sources--
heat and humidity found inside the house or even in a crawl space under
the house. The cooling and the dehumidification are added benefits
during the cooling season. And for those interested in the "green"
factor, only solar water heating has a smaller carbon dioxide emissions
footprint than heat pump water heating.
I belive most window shakers are built to handle ambients right around
95 - 100 F and then then they are running at pretty high pressures.
I'd guess one of these units could generate 110 F water, but for how
long? My guess is not long. It would be similar to running the wife's
mini van at 110 MPH all the time. It'll do it-- for a while.
I've heard of successful conversions of air conditioning equipment to
outdoor pool water heaters in other HVAC forums. The successful ones
know how to braze refrigeration lines and charge the equipment to
optimum operating pressures. These aren't within the normal DIYer
I'm not trying to dissuade you from your project, but there are
inherent limitations when trying to heat water from a unit optimized
for space cooling.
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.