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  1. #1
    Join Date
    Aug 2006
    Posts
    139

    Adding a Heat Pump...Should I?

    I have a vacation home in the Western NC mountains. Someday it may become a full-time home. We're perched on top of a mountain at about 5,200 ft. We have no air conditioning in the house and other than about 5-7 days in August, don't need one. The temperature outside is seldom above 75 degrees. The winters, on the other hand, are fairly cold. Lots of days in the winter around or below freezing (although not Minnesota cold!)

    We have installed a 10 year old Ruud Achiever Plus 120KBTU 94% LP fired furnace which is probably somewhat oversized but sure does heat up the house fast when we visit for a weekend. When we had the furnace installed we had a coil installed because as Floridians, we assumed all homes required air conditioning. (The first summer proved us wrong!)

    Over the years the cost of LP has continued to rise, especially in the last several years. We are currently paying, including taxes and fees, $2.098 per gallon of LP. Electricity prices have been much more stable over the years. Right now we're paying a total cost of $0.194 per KWH.

    So, after this long explanation, do you think it makes sense to purchase a HP, not so much for cooling, but for heating down to 30 plus degrees, then have the LP furnace kick in in a dual fuel setup?

    If your answer is 'yes' would it be important to stick with a Ruud since that's what brand the furnace is? (The furnace is in good shape and I don't plan to replace it anytime soon even though I realize I won't be able to take advantage of a VS motor or some of the new features available in furnaces.)

    Would the coil need to be replaced? It's never been used.

    Thanks in advance for your thoughts.

    Larry Smith

  2. #2
    Join Date
    Sep 2007
    Location
    southern IN
    Posts
    527
    How cold do you keep it when you are not there? If below 60 H.P. not a good idea due to cold return temp..

  3. #3
    Join Date
    Aug 2006
    Posts
    139
    We keep the thermostat set right at 60 degrees when we're not around.

    LKS

  4. #4
    Join Date
    Sep 2007
    Location
    southern IN
    Posts
    527
    With the return that cool your H.P. pressures will run a little low. Still should provide good savinngs on utilities. I prob would do it!

  5. #5
    Join Date
    Mar 2006
    Location
    The South
    Posts
    1,976
    lksmith

    First please re-verify your electric rate. That $0.20/kwh sounds very high for Kentucky.

    How much do you use your home in the fall/winter/spring mths?

    I suspect the coil is wrong and would have to be replaced. Obviously, it should be a matching coil if you go the HP route.

    Here is a fuel comparison calculator that might be helpful. Basically, it shows there is only marginal savings using electric vs propane.

    But if it was my decision and I was considering AC, I believe I would go ahead and get the HP.

    I have to admit I am not a fan of Rheem/Rudd HPs. You are not locked into the same brand as your LP gas furnace.

    IMO


    http://www.warmair.com/html/fuel_cost_comparisons.htm

  6. #6
    Join Date
    Aug 2006
    Posts
    139
    tigerdunes:

    The $0.194 per kwh includes ALL the charges which includes a monthly charge of $17.50 whether you use any electricity or not. If you take out that fixed cost, then the cost per kwh is $0.108. Is that a better number to use in the comparison? I guess if you're talking about the marginal cost of using more electricity to power a HP, the fixed cost is already paid for. OK, so now we're at $0.108 per kwh for electricity and $1.91 per gallon of LP. I assume that tilts the bar even further toward using a HP.

    As far as use of the house, right now, it's all summer, about half the weekends in the fall, Christmas break, and a few weekends during the winter and spring. Down the road that might change to closer to full-time although maybe not so much during the winter months.

    Thanks again for your thoughts.

    Larry Smith

  7. #7
    Join Date
    Mar 2006
    Location
    The South
    Posts
    1,976
    lksmith

    That new electric rate changes things markedly and makes the HP a solid choice. I would want a HP condenser and matching coil to have a rated eff of minimum 14-15 SEER and minimum 8.5-9 HSPF for the size you purchase.

    How big is your home? That's a heck of a large LP furnace with over 100 KBTUs.

    I suggest both a heating and cooling load calculation from your dealer.

    Go for the HP.

    IMO
    Good Luck!

  8. #8
    Join Date
    Aug 2006
    Posts
    139
    tigerdunes:

    Thanks for your comments. The house is about 2650 sq. ft. I remember when the house was being built and the contractor and the hvac guy were standing outside, one said to the other, "Well, how big a furnace you think we need?" The response was, "Oh, I'd say about 120K will heat 'er up OK." That was the load calculation! Back then I wasn't even smart enough to ask how they arrived at that number. Oh well.

    Larry Smith

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