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Old 05-06-09, 06:37 PM   #11
NiHaoMike
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Actually, a heat pump with a COP of 2 would put 3 units of heat into the water for every unit of energy used. It would transfer 2 units from the air and the remaining unit will be from the electricity used. I remember reading that heat pumps use 1/3 the energy as a regular heater so it sounds about right.

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Old 06-02-09, 06:51 AM   #12
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I wonder how well it dehumidifies the air?
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Old 09-02-09, 07:02 PM   #13
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I was getting excited until I ran the calculator & found that switching from my nat gas heater to this would actually increase my Carbon Footprint
This will change depending on dominant electricity sources for the area. I'm in Indiana (so electricity = coal = lots of CO2).
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Old 11-10-09, 07:27 PM   #14
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Quote:
Originally Posted by NiHaoMike View Post
Actually, a heat pump with a COP of 2 would put 3 units of heat into the water for every unit of energy used.
I think if you research this, you will find that the electrical power that is used to run the device is included in the published COP of any vapor-compression heating device, which makes sense, since the electricity used to run the device is virtually all turned into heat.

The opposite is true for vapor-compresson cooling devices.

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Old 11-16-09, 04:02 PM   #15
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Here is a blog post about heat pump water heaters from builditsolar.

Heat Pump Water Heaters - Build-It-Solar Blog

I love the breakdown at the end of the article where he shows lbs of CO2 per kWh of heat gained.
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Old 11-16-09, 06:24 PM   #16
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Neat movie.. That is a versatile unit. But $1,500 ?? That seems a bit much when we
know that it has about the same amount and type of hardware found in a $80 Walmart window AC..

I'll bet AC_Hacker could build one of those air-to-water pumpers inside of 2 weeks..

It would be nice to have one installed in my basement during the summer..
I could turn off the oil burner all summer and pump that warm damp basement heat into the boiler's 76 gallon water-jacket.

The bonus of a cool dry basement and free distilled water? Can't go wrong..

Edit:
I was just peeking at a small Fedders (R22) room AC and it looks like,
IF the copper lines going to the 'hot' coil are top routed. (I can see one is).
that whole heat-exchanger coil could by sat down inside a small tank.
(With the two copper R22 tubes running out the top).

If the tank was an little wider, another coil (for hot water) could also be
placed inside the tank.
The tank could be filled with a heat transfer medium (cooking oil?)
to get a good transfer of heat into the water filled coil..
Of course the tank would have to be well insulated..

The goal:
To use a cheap room AC for hot water, without having to hack into the refrigerant lines.

Anyone think this might be possible?

Last edited by Xringer; 11-16-09 at 06:55 PM.. Reason: Crazy idea:
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Old 11-17-09, 06:04 AM   #17
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Makes sense to me. It might not be well served as a primary heater, but maybe a preheater to your main heater.
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Old 11-17-09, 11:20 AM   #18
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If a little 6,000 BTU AC could pump enough heat into the water jacket of my old boiler
to get the temperature up to 100-120 degrees, I would be very happy..
Our dishwasher has heat-boost, so we don't really need Hot water, just warm..



Use a timer and lite it off from 8AM until noon every day..
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Old 11-17-09, 02:07 PM   #19
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If someone wanted to make their own heat pump water heater out of a window a/c unit it seems like it could be done pretty easily if you use a unpressurized tank of water that has the heat pump in it and a heat exchanger that preheats the water going in to the tank as well as heating it as it is in the tank, even if it just preheated the water it seems like it would help alot with keeping the normal heating elements from kicking on.

My house is set up as a duplex with the water heater on the half that is not really lived in so 95% of the bill is the water heater and the basement dehumidifier for the past 14 months, in the past year of I've installed a timer on the water heater, dropping our water heating bill from $70 per month down to $30 per month (not including any of the meter reading fees) so it's a tough call as to if I should get a heat pump water heater any more at $360 per year cutting my bill in half would be $180 per year, or almost ten years to pay for the unit... of course if I have to get a new water heater any way (they only last so long) then it might be a 5-7 year pay back.
My other idea was to have the cooled air ducted in to the root cellar area, to keep that cool and dry.
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Old 11-17-09, 02:40 PM   #20
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I was just looking at the back of one of the little window ACs and it sure has a lot of exposed heated area..

Around 15x11 inches..

What if, you were to make a flat plate heat exchanger?
A 15x11 metal-to-metal direct-contact heat exchanger and mount it on the surface of the hot coil?

Load up the Hot coil and the 'Heat Collector' plate with thermal conductive epoxy and bolt them together.
Add insulation, re-route the fan power leads to a circulator pump and you are cookin!!

Or maybe if you can make the Collectors thin enough, put one on each side.

When it gets too cold in the basement, the AC thermostat will turn it off..

Spec label:


Last edited by Xringer; 11-17-09 at 05:31 PM.. Reason: Adding Spec label pic
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