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  1. #1
    Join Date
    Feb 2005
    Posts
    2
    My heating A/C is 13 yrs old & not too efficient so I'm concidering a change. I'm looking at using a package unit heat pump or gas outside furnace with A/C. Can I expect the life & efficiency to be the same for a package unit as compared to a conventional split unit? Also, how easily can a ground source heat pump be retrofitted in an existing residence and can you give the approximate percentage increase cost over a package unit? I think my lot would be sufficient for burying the required length of pipe. I presently have

  2. #2
    'Can I expect the life & efficiency to be the same for a package unit as compared to a conventional split unit?
    '

    ME: Youll have more (higher) efficiencys to choose from on a split system that you will with a Package Unit youll find. Life expectancy , assuming both were installed correctly, would be roughly the same. The advantage you have with the packaged unit is that its a Factory 'PreEngineered' Unit .

    'Also, how easily can a ground source heat pump be retrofitted in an existing residence and can you give the approximate percentage increase cost over a package unit?
    '

    ME: Normally, its not much of a problem retrofitting ; just alot more money and longer payback due to the installed cost.

  3. #3
    As the owner of a smalll HVAC shop I would say

    Life expectancy is generally accepted as ten to fifteen years I wouldn't get hung up on that point. There are to many varibles to consider and probably won't make a big difference in either one you choose, I always felt that a Heat Pump in combination with a gas furnace, sequencing the Pump to run down to about a 45 OA temp then switching to gas heat was the best thing going. SEER ratings are just what they say they are if you want more eff. get a higher SEER rated unit.

  4. #4
    Join Date
    Feb 2005
    Posts
    2
    Thanks for the help guys. What I would really like to do is install a ground source heat pump. Would the price climb dramatically for geothermo heat and cooling?

  5. #5
    Join Date
    Apr 2004
    Posts
    7,680
    Get a quote, but yes, in a new install you can expect to pay nearly 4 times as much.

  6. #6
    Originally posted by fat eddy
    As the owner of a smalll HVAC shop I would say

    Life expectancy is generally accepted as ten to fifteen years I wouldn't get hung up on that point. There are to many varibles to consider and probably won't make a big difference in either one you choose, I always felt that a Heat Pump in combination with a gas furnace, sequencing the Pump to run down to about a 45 OA temp then switching to gas heat was the best thing going. SEER ratings are just what they say they are if you want more eff. get a higher SEER rated unit.
    Any particular reason for the 45*F outside temp. for heat pump balance point? Is it because of the climate in your location?
    Doesn't the size of the heat pump, relative to heating load, also determine the optimum balance point?

  7. #7
    Assuming that the heat pump $/BTU is lower than gas $/BTU, wouldn't it make sense to run the HP with gas firing only as aux heat? Even at 17 degrees outside, most modern HP's are well over 2 COP (over 200% efficient); most around 2.5 if I remember.

    Running a quick calculation, in philadelphia suburbs (PECO/Exelon), if you don't have the RH (electric heating) rate, you pay around $0.13/KWHr, and around $1.14/therm(or ccf). At that rate, with a HP COP of 2.5 and a furnace efficiency of 85%, the HP and natual gas are basically tied on cost. However, if you have the RH rate ($0.063/KWHr after the first 600 during winter), then the heat pump is 1/2 the cost of natural gas, even at outside temps in the teens. Obviously, at higher temps the COP rises up to 3.5ish, making it a win even at full electric rates.

    We'd assumed RH rate was not available if you used gas or oil for aux heat, but a friend who bought a townhouse here just qualified for RH with a HP plus gas aux, and he didn't hide the fact from the guy who came out from PECO. Don't take that as gospel, though.

    PECO electric rates are among the highest in the country, so I imagine in most areas (avg electric rates of circa 8-9 cents) it always will be cheaper to let the HP do all it can, even down to 0 or below (I don't think most HP's drop below 2 COP until temps are below 0), using gas (or whatever) to make up the BTU difference once you're below the balance point.

    We supplement ours with a small wood stove (~24K-30K BTU when running), especially when the temps are 20's or below. Gas isn't an option for us, propane is even more expensive and we'd need to hide a big tank somewhere, and our house is split into three poorly-connected sections, making it "fun" to have a unified furnace (plus the basement is 600 sq ft of small rooms - only one even theoretically possible to put a furnace/boiler in).

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