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  1. #1
    Join Date
    Mar 2019
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    Propane furnace and heat pump better than the same propane furnace and AC? (MA)

    Both propane furnaces are 96% efficient, two stage, variable speed. One contractor is quoting a heat pump for AC in the summer and also to help heat the home in the milder months without using the furnace until temperatures drop below 40 degrees or so.

    The other is quoting a dedicated AC for cooling demands. Electric is really expensive in MA, 22cent/kwh. How can I figure out which solution is best?

    The house was built in 2002, MassSave audit recommended no insulation upgrades. We are the type of people to turn it down while we are not home and also when we go to sleep if that matters.

    Cooling demand of the house is much larger, it faces south and has a lot of windows. Is saving propane with a heat pump for the mild months worth it with such a good furnace? Does a heat pump or dedicated AC provide better cooling in the summer if they are sized the same?

  2. #2
    Join Date
    Jan 2010
    Location
    Central Texas
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    The Heat Pump and AC capacities are the same in the Cooling mode, assuming that the capacities are rated the same. It's just the ability to use the refrigerant to absorb heat from outside to heat the house.

  3. #3
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    Mar 2019
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    Thread Starter
    That is what I thought. So how do I choose between heat pump or AC? Is a heat pump less reliable because it works more than just an AC? To me a heat pump seems good for heating the milder months but with electric so expensive and the furnace so efficient would it pay off over 5 to 10 years?

  4. #4
    Join Date
    Jan 2010
    Location
    Central Texas
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    There are several brands that offer Dual Fuel systems. I'm most familiar with the Carrier Branded systems, so that's what I can discuss most. Others might have the same, just not certain on them.

    With the Carrier branded systems, in their communicating systems, you can set the cost for the electric and gas cost. Then the thermostat can evaluate the conditions and determine which system would be the most efficient heat source.

    The reliability of the system doesn't change much between the Heat Pump or AC system. Heat Pumps do tend to have additional safeties in them, so they do tend to be protected if there is a failure.

    The choice of using a Heat Pump Dual Fuel or a Propane heat system usually comes down to Propane usage. With a Propane only system, you would be using the propane during mild weather, which can deplete the propane tank and leave the tank empty in the time of need.

    Many homes in the Colorado Mountains use Dual Fuel so that it limits the draw from the tank.

  5. #5
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    Mar 2019
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    Thread Starter
    But since the furnace is variable speed and can run down to 5% won't it use such little fuel in the mild months?

  6. #6
    Join Date
    Jan 2010
    Location
    Central Texas
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    The Blower is Variable Speed, the Burners are 2-stage, so it would have a reduce consumption of fuel on low stage but it would still be consuming fuel.

  7. #7
    Join Date
    Nov 2004
    Location
    SW FL
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    $_._ LP / gallon for YOU ?

    Heat Pump C.O.P. at 34'F might be ~ 3.4
    Effective cost would be $0.22 / 3.4 = $ 0.065 / Kw-Hr

    https://ycharts.com/indicators/massa..._propane_price
    Designer Dan
    It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE

    Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities

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