Water heater heat pump.
 

Has anyone else looked in to this?
Airgenerate.com | Adaptive Energy Solutions
It's a heat pump that sits on top of your water heater.
I wrote them a few questions, such as what it's efficiency is in a basement at 55F as their numbers are all base off 68F, I also asked if they have any problems being hooked to a timer and only coming on a few hours per day, so hopefully in a few days I'll have some answers.

I've heard of them before, but I don't really know much about them. Overall cost of the unit + fuel I think tends to be equal with a conventional unit. In this case, the unit is more expensive, but fuel costs are lower vs the opposite.

What about build one using parts from a cheap window or split unit A/C?

I figure if their numbers are correct it would pay for it's self in 3 years, my co-home-owner likes the idea of have a dry basement so it would eliminate the need for a dehumidifier down there in the summer and help keep it cooler down there in the summer as well, in the winter we have to heat the house anyway, so it's either the electric heat leaching out of the water heater or it's the cheaper natural gas.
I'm sure that for $700 in parts you could get something that would heat your water, but it might cost alot more making units that don' work, this one they claim can take as little as an hour to install and that has alot of appeal that it's a complete ready to install unit that is self contained.

I'd love to see some kind of integrated AC-refrigerator-water heater system. The water heater produces cool air as waste, while the fridge puts out heat. If you can get them talking to each other, they both win.

Since a heat pump is based on the temp difference, you will extract less heat from 55deg than from 68deg, but it should still work. Also, the heat pump might take a longer time to get you water up to temp, making the timer have to be 4 or 5 hours instead of 1 or 2, but that would be a "try and see" kind of thing. Hopefully they will get you accurate answers to your questions.

Here is the Email I sent them and what I got back:

-----Original Message-----
Sent: Saturday, May 02, 2009 9:42 AM
Hello,
I was looking at your chart of coefficient of performance and noticed that
it does not give the most common ambient temperature that surrounds a
water
heater, that being the 55F of a basement and so I was wondering what that
number is.
I would also like to know how well your product works with a timer as I
currently have my water heater come on for two hours in the morning and
two
hours in the evening, would this void my warenty or cause any other problems?

>>>>>

We appreciate your interest in our AirTap product!

The testing for our unit's ratings were done per Department of Energy
guidelines with the water temperature being 58'F, and the ambient air
temperature being 68'F. This testing resulted in a COP of 2.5.

We've attached the AirTap informational flyer with the COP at different
temperatures. At 40 F, the COP drops 20% to 2. It is recommended that the
AirTap be operated at temperatures of 50 F and higher for greatest
efficiency. While we do not have an exact COP for 55 F, we do know it will
be between 2 and 2.5.

Also, running your AirTap with an electrical timer should cause no problem
with the AirTap's operation, and will not void your warranty. Just make
sure that the timer supplies the AirTap with a dedicated 15 amps of 110V
current so that there are not any current allocation issues.

Thanks, and if you have any further questions, please feel free to contact
us here at the Sales & Support Center!

-Jason

Jason Baker
AirGenerate Support Center
713.574.6729 option 2
support@airgenerate.com

What is COP?

That's a measure of efficiency of a heat pump. It is energy transferred over energy used.

COP is coefficient of performance, or the comparison of how much energy it takes to heat or cool, if I can create twice as much heat in the tank of water with a heat pump per watt of energy then I would if I just had a resistive heating element, then it gets a rating of 2, not great for a heat pup but it would meen your water heating bill would be half.

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.

I wonder how well it dehumidifies the air?

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).

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.

-AC_Hacker

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.

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.. :D

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.. :thumbup:

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?

Makes sense to me. It might not be well served as a primary heater, but maybe a preheater to your main heater.

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.. :)

http://i46.photobucket.com/albums/f1...HSTARMOT35.jpg

Use a timer and lite it off from 8AM until noon every day..

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.

I was just looking at the back of one of the little window ACs and it sure has a lot of exposed heated area..
http://i46.photobucket.com/albums/f1...r/NCL/F001.jpg
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:
http://i46.photobucket.com/albums/f1...NCL/F007-1.jpg

I'm picturing something like this:
http://i46.photobucket.com/albums/f1...r-pipework.jpg

Insulated on one side and a flat metal (15"x11" sheet Aluminum?)
on the other side. This solar exchanger looks pretty easy to build..
Need to find out how to bond the copper tube to the sheet metal.

I was also thinking of a welded aluminum tank. 15"x11"x2"
with two 1/2" pipe fittings on one edge. Maybe some sheet metal
baffling inside to make the coolant circulate over all 165 sq inches
of the contact plate.?.

Comments please..

Wouldn't it be better to make heat exchangers by threading copper tubing through large PEX or PVC pipe?

It needs to fit flat against the 15"x11" hot coil of that GoldStar (LG) AC..
So, a round pipe wouldn't work.

Take a look at this little CPU cooler. (Heat exchanger).
http://www.build-your-own-computer.n...cooling-03.jpg

Picture this thing made 15"x11" with the copper part epoxied to the back
end of the GoldStar AC.. (with insulation over everything).

Here's a DIY version..
Zapi Liquid Cooled Heatsink

I remember about some overclockers cutting away part of the A/C to put the evaporator into a tank of water to make a water cooler.

Maybe do the same but with the condenser, put it in an insulated container of water and then add a coil of copper tubing as a heat exchanger?

I saw some of those over-clockers postings last night.
And putting the condenser in a little tank was the first thing I had considered.
But, I think that a flat contact 'heat collector' mounted on the back side
of the AC might work too.
The reason: No need to remove the condenser and chance a leak.

Just remove the fan & fan motor and install insulation on the inside.
Or, install a second 'heat collector' on the inside of the condenser,
sandwiching the condenser between two heat collectors.?.
(With good insulation over the exposed areas).

The collectors could be mounted using heat conductive epoxy, or
with hardware and heat-sink compound. Something thick
that won't run down when it gets too hot.

Install a water drain hose on the bottom and use the motor AC lines to power a pump? Not a lot to the project..

A/C Hacks...
 

This all sounds like great fun!

Please remember to take loads of photos & notes when you actually do it.

One thing to keep in mind is that the A/C units are designed to use the fan air to blow past the compressor and assist cooling. Before you hack into the unit, you should let it run for a half hour or so, like maybe sitting on th floor in your basement, then turn it off, remove the cover and take a temp reading of the compressor, for future reference...

Sounds like the adventure is beginning.

Best Regards,

-AC_Hacker

P.S. BTW, I just made a related post here.

Maybe install a 120vac 4" muffin fan to keep the compressor cool?
Maybe custom build a wrap-around heat-sink for it?
Hook the heatsink up to a little heat-pipe routed from the cold-air output vent..

That related post sure was interesting reading. :)

What I'm saying is that it's a good idea to know what the original working temp of the A/C compressor is, for future refererence. You may not need the muffin fan or any auxillary cooling at all.


Interesting ideas, but if you're gonna wrap anything around the compressor, it should be copper tubing or some kind of water jacket, going to the water storage tank. You don't want to just throw that heat away, you've already paid for it.

* * *

It has been very interesting for me to disassemble air conditioners and look at how they're made... they're made by the millions.

Part of the design criterion is efficiency, all well and good.

But another very large part is cost-reduction.This is done to expand the potential pool of buyers and of course, it also results in higher profits for the manufacturer. But sometimes the cost-reduction measure may be at the expense of efficiency. Over a production of millions of units, these decisions may be best for a company.

But for us, the Hackers & Modders of the world, the criterion is competely different. We aren't making a million units, we're just making one, or at the most a few.

Anything we can do that will increase efficiency will benefit us in the long run.

Something to think about...


-AC_Hacker

Coil a foot or two of copper tubing around the compressor, tighten it up, and slip it over the top. Then run the hot water through it after the regular heat exchanger.

If compressors really got that hot, it seems like the design would include at least a few heat sink fins..
But, I just took another look at the unit on my operating table and it does seem that
it's positioned near the center of a side input vent for outdoor air.
I've taken out all the screws and the front panel won't pop off.
And the rear sheet metal cover (lip) is stuck inside the unmovable plastic cover!


Mike, would not try to use the main input-output line, since the OD of that line is going
to be large. Not easy to bend stuff.

I've been eyeballing the Taco 007 pump used for the basement zone.
Taco 006 Pump, Taco 007 Pump, Taco Pumps 008, Taco Pumps 009, Taco Pump 0010, Taco Pumps 0011

The basement zone is never used in warm weather.
So if I added some taps and a cutoff, maybe I could substitute my Heat Collector for the basement zone.
I would switch out the normal relay box and use an SS relay to drive
the pump motor, using a speed control.?.

I'm thinking it might have some kind of starter capacitor under that cover.
And I'm wondering if this type of motor would work with a triac speed controller?

Seeing as how you get more heat out of the hot side with warmer air going over the cool side, then it seems like as you cool the compressor you should have that heat heat the cold side of the heat pump, that is assuming that the compressor is only getting in the 100 degree range or so, if it's hotter then that then I would be a little worried.

Look for more screws.

Look underneath, see if there are any little plastic panels that will open to reveal screws, Look again on the sides. Those little screws really have a way of hiding.

If all of that fails, repeat this mantra:

"It's all for science, it's all for science, etc."

Keep repeating the mantra while you start jimmying the plastic stuff around the edges. Something's gonna start coming loose eventually. If it's all loose except for one area, look again for a screw in that area.

REMEMBER, Freon is odorless and not poisonous, or flammable but it can displace air in your lungs which can kill you. If you start hearing an angry hiss, make sure windows and doors are open and beat a hasty retreat.

You'll get all of the stuff off eventually... just go slow.


Regards,

_AC_Hacker

There are only two screws on the front plastic cover. Nothing on the bottom.
I've tried jimmying around the edges and messed up the plastic.. But no joy..

Today, I dehumidified my basement for about 2.5 hours. When I remembered
I had left it on, I went down and scanned the compressor (via the vents) and
it was still about 98 deg F. Never really got that hot.
Maybe the R22 flowing inside it keeps it cool?
The test wasn't too stressful on the AC, since it's 65 down stairs already.
It wouldn't come on, until I set it for 60..

It was pumping out some real cold air, but heat from the hot coil
wasn't that impressive. Got up to about 92 and that was it.

Maybe it will do better in the summer, when it's 10 degs warmer down there..

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