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Old 10-26-2009, 08:56 PM   #1
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Heat Pumps??


I have an all elecric house. I have heard both sides of the story about Heat pumps, the good and the bad. The truth is I don't know anything about either. First of all, what is a heat pump? How could it benefit or not benefit my home? Any information is greatly appreciated.

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Old 10-26-2009, 09:04 PM   #2
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Heat Pumps??


Udall KS...Hum

I live in hays ks and I have a heat pump. Simply enjoy it

How it works is that (simply put) the flow of freon is reversed and the indoor coil is the condenser and the oudside unit (condenser) is now the evapator..Again simply put

When looking at this you need to check to see what in BTU's is more cost effeticent. Gas or electric for the second stage heat.

The first stage heat is the heat pump but as the temp outside drops so does the effeicy of the HP

If you live within one of those small town COOP's or REA's for electric you may want to go with LP or Natural gas for the second stage heat.

We use the HP until it reaches 38-40 deg outside and then we switch over to pellet stoves since my second stage heat is a 20k heat strip

Where us Udall

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Old 10-26-2009, 09:34 PM   #3
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Heat Pumps??


You can heat your home with a heatpump pulling less than 50% of the amperage of heat strips.

I've seen heatpumps pulling 9 to 12 amps. Heat strips pull @ 20 each and you would probably need at least 2 to 4 strips to comfortably heat your home.

A heatpump would require heat strips for auxillary or emergency heat, but these would not run as often.
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Old 10-26-2009, 10:50 PM   #4
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Heat Pumps??


Your average January low temp is 19 degrees with a heating season of over 400 degree days. If you get a properly sized heat pump with high enough efficiency, you could conceivably get 100% of your heat load satisfied by the HP down to 30 degrees or so. Depends on your heat load, which you can determine by doing a manual J calculation. Don't guess at it. You'll need some backup heat, which can be electric heat strips in your case. Consider staging your strips, i.e. use 5 KW, then 10 to augment the HP when it can't supply all of the heat. Will need a 3-4 stage thermostat to do that. Done properly, you'll be able to max out on the use of the cheap HP heat, adding only as much extra heat strip heat as you need to support your temp setting. What's more, if you get a multi-stage HP, you'll consume even less energy on those days when it is warmer out (say above 40) and you don't need to have the HP run at full capacity.

Last edited by HPGui; 10-27-2009 at 01:28 PM.
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Old 10-27-2009, 07:54 AM   #5
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Heat Pumps??


A heat pump is essentially a split system A/C with some extra controls, reversing subsystem, and different sized coils to optimize heating. It seems counter-intuitive, but yes you can extract heat from 20F air and heat your home.

Just like an A/C the performance changes the greater the lift (outdoor to indoor temp delta), and hence your operating costs change. Your cost to performance ratio (aka Coefficient of Performance), or efficiency as some like to call it, can range up to 400% as compared to 100% for electric resistive heat. Most folks switch over to an alternative heat as the efficiency approaches 100%, but as you can see the operational cost advantages are substantial. Heat pumps and geothermal units sit close to the top of the list for the most efficient way to heat your home.

I resurrected my aging York 12 SEER unit when propane prices spiked, and began burning wood more frequently. My electric bill has hardly nudged, but my propane costs have dropped significantly.
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Old 12-30-2009, 05:42 PM   #6
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Heat Pumps??


Quote:
Originally Posted by dac122 View Post
It seems counter-intuitive, but yes you can extract heat from 20F air and heat your home.
Think of it this way:

20F outdoor air is going to warm up a coil that is 5F That's how you extract heat from cold air. You make the outdoor coil colder then the air, no matter what the temperature.

That is the same way AC works. If it is 100F outside, you make the outdoor coils 120F and you pump heat from inside to outside.

The problem is that your heat pump or AC unit has to do work to take 70F air and pump it down to 5F if you're doing a heat pump cycle. Or take 70F air and pump it up to 120F if it's an AC cycle. The machine has limits on it's ability to compress the refrigerants in order to do this. So the farther away from 70 degrees you get the less efficient the pumps compressor gets at doing it.

-Jeff

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