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  1. #1

    Hybrid System -Outside Temp - Switch to 80 NG Furnace

    I tried to glean the answer from previous posts. I know it has been asked and answered before but I can't seem to find an answer I can understand!.

    I had a 16 SEER - York hp installed in the spring. And I didn't pay much attention to the part when they discussed when the system would call for the 80% York variable speed NG furnace.

    I called York and got their local representative to call me back (after about two weeks!) I believe when the system was installed they set the outside temp at 20 degrees before NG furnace would be called. The York representative said that as long as the inside set temperature (71 degrees) could be maintained the setting was good. In other words if it couldn't keep it at 71 degrees the balance temp should be raised. The hp is running constantly to maintain 71 degrees in the low 30's and its not gotten lower then mid 20's so far this winter. However the 71 has been held.

    Questions: How do I determine the correct outside temperature to have the contractor set the point to switch from the HP to gas? With my experiences with this contractor I would rather tell him than he tell me! Also is the temperature measured at the hp, I don't see any kind of external device?

    Finally, York claims for this hp to be the quietest on the market. It is noisy as he*l. Especiallly at start-up. Almost sound 'bearing" like but the noise changes. I had the installing contractor come out (biggest in my city) and they put some strips on it to help with vibration but this sounds more motor like. The tech sounded like this was a known problem? Since the unit is by our bedroom this is not ideal!

    Your help is greatly appreciated.

  2. #2
    Join Date
    Jan 2004
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    Lancaster PA
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    Might be overcharged.

    Probably 20 or 25 will be your temp to switch. As far as when the heat pump can't keep up.
    It is normal for it to run continuous near its change over temp.

    As far as economical balance point. That depends on your electric and gas rate.
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  3. #3
    Join Date
    May 2007
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    732
    The balance point temperature is the outdoor temperature at which the amount of heat being introduced by the heat pump exactly equals the amount of heat being lost by the structure. At balance point the heat pump will run continuously to maintain indoor temperature. When outdoor temperature drops below balance point the heat pump is no longer adequate for maintaining indoor temperature. Balance point is first determined from an accurate load calculation. Even then, exactly evaluating all variables can be so difficult and time-consuming that a load calculation based balance point is more of an educated best guess. How good of a guess depends on the experience of the contractor and how much time he can devote to pinning down the variables. Final balance point can only be determined by trial-and-error. You report to me, the contractor, that the indoor temperature is dropping and the heat pump is running continuously. I come to your house and confirm that the heat pump is working correctly. After confirming correct operation, I raise the balance point setting. I would include an allowance in the original quote for adjustments like this. Other contractors may or may not allow for this. Since things like this increase the cost of business, if the work you received was the lowest bid, it may be reasonable for the contractor to charge for this service.

  4. #4
    Join Date
    Sep 2002
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    Northeast Ohio
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    Your location is not in your profile but I will assume since you had a new 80% furnace installed you are near or south of the Mason Dixon. As BT stated the balance point of capacity is different from the economic balance point. The economic balance point will fluctuate because of the rise and fall of utility costs. In our area, NG is at a really low cost right now and we have raised the balance point on our HP installations (most are set at 40) to coincide. While 20-25 may well be your capacity balance point, your economic balance point could be considerably higher. The switch over of your system from furnace to HP is most likely controlled by your thermostat. There will be an outdoor sensor wired in and the balance point will be changed in the thermostat setup program. As for noise, that is a relative term but compared to the other brands, Yorks higher end equipment is on par with the other manufacturers.
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  5. #5
    Thanks for all of the input.

    One final question, why wouldn't I want the most economical balance point? I'm thinking it would be less work on the HP, which would make it last longer if it wasn't running all of the time.

    If any one can help with the calculation I would be appreciative. Here are the factors.

    NG - Cost per therm is .66. Electric is .6302 per therm.

    I live in St. Louis. Thanks again.

  6. #6
    Join Date
    Nov 2000
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    Eastern PA
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    68,944
    Quote Originally Posted by bluesramsrock View Post
    Thanks for all of the input.

    One final question, why wouldn't I want the most economical balance point? I'm thinking it would be less work on the HP, which would make it last longer if it wasn't running all of the time.

    If any one can help with the calculation I would be appreciative. Here are the factors.

    NG - Cost per therm is .66. Electric is .6302 per therm.

    I live in St. Louis. Thanks again.
    There is not much of a wear factor for a heat pump to run continuosly. What mostly wears out compressors is them starting up. A long running heat pump is an efficiently running heat pump, as long as it is charged properly.

    Living in St Louis, I would rely on the heat pump to do most of your heating.
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  7. #7
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    Dec 2007
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    I would agree your balance point should be closer to 40° since the HP looses considerable capacity below 32°
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  8. #8
    Join Date
    Nov 2000
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    Eastern PA
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    Quote Originally Posted by Texas-Tech View Post
    I would agree your balance point should be closer to 40° since the HP looses considerable capacity below 32°
    Since the heat pump is still maintaining the temperature below 32 degrees, it obviously has enough capacity to do the job.
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  9. #9
    Join Date
    Jan 2004
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    What model number is the heat pump. Also need to know its COP. If you post the model number of the outdoor unit, and indoor coil. We may know its COP at different outdoor temps.

    With the info you posted. Your gas furnace is more efficient any time the heat pumps COP is below 2.1
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  10. #10
    YP8C100C20MP11 - Furnace

    YZH04811 4Ton 18 SEER 2 Stage Heat Pump (I had originally posted 16 SEER)

    YE48160E210 Matching A Coil

    Thanks!

  11. #11
    Join Date
    Jan 2004
    Location
    Lancaster PA
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    68,058
    I don't have a listing for that indoor coil.

    But. For all the coils I have listed. None of them drop below a COP of 2.5 at 10°F.

    So what ever temp your heat pump can't maintain indoor temp(as long as its above 5°). Should be your switch over point.
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