# Heat water with a window AC?

• posted on July 20, 2006, 2:48 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.
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

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• posted on July 20, 2006, 11:34 pm
snipped-for-privacy@ece.villanova.edu wrote:

I like your thinking, it should work. I take it your not really thinking 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:
http://tinyurl.com/zpkpd
and:
http://www.aceee.org/consumerguide/topwater.htm
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.)
Jeff
--
Jeffry Wisnia
(W1BSV + Brass Rat \'57 EE)

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• posted on July 21, 2006, 1:19 am
snipped-for-privacy@ece.villanova.edu wrote:

I have a better idea. Cool your house from the coming winter cold or the past one.

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• posted on July 22, 2006, 2:57 am
yaofeng wrote:

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 winter.
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.

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<%-name%>
• posted on July 21, 2006, 2:42 pm

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?

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• posted on July 21, 2006, 6:44 pm

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

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<%-name%>
• posted on July 22, 2006, 12:42 am
wrote:

That they do.

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• posted on July 21, 2006, 7:34 pm
snipped-for-privacy@ece.villanova.edu wrote:

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

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• posted on July 21, 2006, 9:35 pm
Claude wrote:

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)

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• posted on July 22, 2006, 5:43 pm
snipped-for-privacy@ece.villanova.edu wrote:

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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• posted on July 25, 2006, 10:45 am
wrote:

Haier
coil
replumbing or

SB1-20
cold
window shaker. The whole mess is on a little cart, along with a circulator pump. In the spring I roll it out beside the aboveground pool and in about a week the water is in the 80's. I also have a desuperheater on the house A/C that makes free hot water.

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<%-name%>
• posted on August 8, 2006, 5:23 am
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 skill set.
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.
Greg snipped-for-privacy@yahoo.com wrote: