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Heat water with a window AC? nicksanspam 07-20-2006
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Posted by on July 21, 2006, 2:44 pm

>> 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.
>
>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?

Yes, with an existing conventional tank water heater. Powertech, Ltd has
an air conditioner something like this...

Nick


Posted by News on July 21, 2006, 8:42 pm

>
>>> 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.
>>
>>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?
>
> Yes, with an existing conventional tank water heater. Powertech, Ltd has
> an air conditioner something like this...
>
> Nick

That they do.


Posted by Claude on July 21, 2006, 3:34 pm
nicksanspam@ece.villanova.edu 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
> 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.
>
> Nick
>
How about putting a water heater behind the refrigerator using it's hot
coils.
Another thing, have an air duct from the fridge to outside. Suck in
(under thermostatic control) cool air from the outside for the fridge
and when it's really cold, for the ice box.

--
Linux is just a fancy name for Windows blocker.

Claude Hopper

Posted by Jeff Wisnia on July 21, 2006, 5:35 pm
Claude wrote:

> nicksanspam@ece.villanova.edu 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
>>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.
>>
>>Nick
>>
>
> How about putting a water heater behind the refrigerator using it's hot
> coils.

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...

Jeff

<snipped>
--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
"Rudeness is the weak man's imitation of strength."

Posted by on July 22, 2006, 1:43 pm
nicksanspam@ece.villanova.edu 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


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