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Old 03-05-16, 07:21 PM   #1880
jeff5may
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Quote:
Originally Posted by DonT View Post
So, just to be clear. What you are saying is it will NOT work. The 11350btu R22 compressor will not heat a tank of water to more then about 130F.
No, what I am saying is that what you have set up now is not what a heat pump is good at supplying at high performance. With YOUR weather conditions, it would be nearly impossible for ME to over-insulate the building on a bang-for-the-buck basis. With (only) an 80 KWH daily heat load in January, it would be incredibly difficult for ME to justify spending more than a couple thousand dollars and/or a couple hundred man-hours on a heating system retrofit. Especially with a medium-temperature floor heating loop that would need a gut and redo. Reducing your heat losses chops your energy bill the same way as a more efficient heater, but is much more permanent. Because three blankets over you in bed beats one blanket and a dog when it's really cold, and dogs eat more than blankets do.

Yes, there are systems on the market (Japanese Altherma and Eco Cute, European Nibe, American Geyser) that can do an awesome job of heating water to above 150 degF, even with air-source outdoor units at low outdoor temperatures. Yes, you could assemble one of these beasts. I would recommend a 2 ton "pumpkin" compressor with lots of shell surface area, along with an oversized ground loop filled with vodka or 50/50 antifreeze. Even then, I would still keep your existing water heater boiler, just in case.

For what you have described, it would be very easy for me to justify a couple thousand dollars worth of sealing and insulating materials (plus effort), combined with a modest (1-ton) inverter mini-split-style ground source (or...ahem... air source) style of unit. A single zone unit could quite possibly keep the water heater from burning 3/4 of the time, and the envelope could be made 25% (or more) tighter. The combination could cut your electric bill in half.
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