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  1. #1
    Join Date
    Nov 2005
    Posts
    2
    We are replacing a 13 year old heat pump system and considering a duel fuel system(heat pump as primary with propane backup). We already have a propane cooktop and clothes dryer. We live in the Washington DC area and our house is roughly 3200 sq ft above grade. Our current gas consumption is only 4 gal/month (47 gal/yr). The system we are considering is a Carrier 38YXA030 2.5 ton 14 SEER Puron system with a 58MVP060, 94% AFUE 2-stage variable speed furnace and CK5PX030 evaporator coil. We will also be using the Infinity controller. Note that there will be a separate straight heat pump system for the upstairs.

    My question is this: Can anybody estimate how much propane we will consume in an "average" Mid-Atlantic winter? The only outstanding issue is whether 2 100 gal propane tanks will be big enough, because we can not use a 500 gal tank and don't want to install a 3rd 100 gal tank. If we can't reasonably get away with using just 2 100 gal tanks, we will probably forgo the propane backup and go straight heat pump, although this will make me very unhappy.

  2. #2
    Join Date
    Feb 2003
    Posts
    1,996
    It would probably be impossible to estimate. But do you expect to only fill the tanks only once all year? You probably could get away with a fill up in the Spring and Fall to avoid peak LP prices. Can't you get a burried 500 gal tank?

  3. #3
    Join Date
    Nov 2005
    Posts
    2
    Unfortunately we can't do an underground tank due to lack of space and water table issues. Our current propane tank is filled twice a year (spring and fall), even though it's a 45 gal tank and we only use 47 gal/year. I'm okay with having to do multiple fill-ups, but I don't want to risk running out of gas or having to fill up every two weeks in the winter. Filling up once in October or November and again in January or February would fine, though.

  4. #4
    Join Date
    Feb 2003
    Posts
    1,996
    Get a duel fuel thermostat and lock-out the LP furnace until it gets below freezing.

  5. #5
    Join Date
    Mar 2004
    Posts
    1,042
    If the straight heat pump will make you very unhappy because of the comfort you've come to expect out of your old heat pump, forget about that. Old heat pumps weren't comfortable. Nice new ones can do very, very well, though.

    Since you're already looking at Infinity, I would suggest swapping out the MVP furnace for the FE4-series air handler. Matched with the correct multistage heat strips, such a system will never offend you by putting out tepid air in heating season. You effectively get four stages of heat (one from the heat pump and three stages from the heat strips). That pairing should be cheaper than using the furnace at all, even ignoring the concerns of needing a larger propane tank.

    I have an FE4ANF006 air handler with the 3 ton YXA heat pump, and couldn't be happier with the comfort and energy costs.

  6. #6
    Join Date
    Feb 2005
    Location
    Richmond
    Posts
    480
    DEFFENTLY get the 58MVP Carrier Infinity. Variable speed(ECM Motor) is DEFFENTLY the way to go. Much better comfort because of slower speed of fan and constant, quiet circulation. Also cheaper to run than a standard (PSC) Motor. But way more expensive to replace(Change your Filter!) Go with the 38YXA unit, which is really rated at 13 SEER but with the 58MVP the SEER will really be like 15. The ECM Motor will help maintain a more constant temperature in the summer, and will offer good dehumidification control. If you get the Infinity control to go with the furnace, you will have a VERY nice comfort control system. You can add an Outdoor Temp. Sensor to lockout the furnace above a certian temperature (Such as 32 degrees F) The Infinity control your Humdifer, Fresh Air ventilator, will control space humidity in summer and winter,and will monitor your air filter and tell you when to change it. Later, you will even be able to acess the system control away from your home via internet or phone. I am getting an Infinity System almost the same as you for my new house in Loudon County, Northern VA.

    -York_Hvac

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