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  1. #1
    Join Date
    Dec 2008
    Location
    Montreal
    Posts
    3

    Lennox HeatPump Questions

    {I am re-posting here as it seems to be a more appropriate place}
    Hello everyone. Great Forum!

    I have a lennox heat pump (X13, I believe...about 2 years old) mated with a 15 year old Heil Gas forced air furnace and a Honeywell 7400 thermostat. I am on a dual energy system and have a changeover relay that automatically locks out the heat pump when the temp hits -13C.

    On to my question:
    Lately, I have noticed that when it's colder out (between -6 and -10C) when the thermo calls for heat, the heat pump starts up, runs for about 30 to 45 seconds then shuts off and the gas comes on. I am pretty sure this is not happening because the temp drop is too low, because often the thermo starts calling for heat when the ambient and set temp are the same.

    I don't seem to have this problem when the temp is warmer than about -5C, the heat pump seems to put out good heat (air from vents is fairly warm).

    I imagine I will have to call a technician to look into this- just wondering if there is anything I can check for myself and would also like to know what to expect from the technician.

    Thanks in advance for your input.

    Derek

  2. #2
    heat pumps start to lose efficiency at about 45 degrees fahrenheit so -5 celcius is way too cold for the heat pump to work so your system is compensating by using your auxillary heat to warm your house

  3. #3
    Join Date
    Mar 2003
    Location
    PA/DE area
    Posts
    1,535
    I looked at the temps ,then I realize it was in C not F
    It's NOT the BRAND,it's the company that installs it!!!!!

  4. #4
    Join Date
    Jul 2004
    Location
    Massachusetts
    Posts
    6,841
    Nothing you can check. Have the service company do their thing and you should get it resolved. I don't believe the HP outdoor unit should fire at all below the lock-out temperature.
    If YOU want change, YOU have to first change.

    If you are waiting for the 'other guy' to change first, just remember, you're the 'other guy's' other guy. To continue to expect real change when you keep acting the same way as always, is folly. Won't happen. Real change will only happen when a majority of the people change the way they vote!

  5. #5
    Join Date
    Jan 2007
    Posts
    1
    Get a professional to look at the system. I would not operate the heat pump under 2 Degrees C for maximum efficiency. I would ask your contractor about the Honeywell vision pro 8000 thermostat with outdoor sensor. You can set the outdoor lockout temp on the thermostat. you will be able to see the outdoor temp on the thermostat and it will not allow the heat pump to run below your lockout temp. no questions whether should it be running or maybe not.

  6. #6
    Join Date
    Nov 2008
    Posts
    8
    Ok I have to ask about min temp for HP.

    Why wouldn't he run the HP down to -5C ? Even at -5C (23F) my HP has COP of 2.4. ( I imagine that his is similar) If his thermal balance point is -5C the HP is still over 2 times more efficient than Electric and cheaper than NG ?
    (Even at -8.5C, my HP produces 23000Btu's )


    Just wondering.

    GC

  7. #7
    Join Date
    Jul 2008
    Posts
    551
    Quote Originally Posted by Gary-co View Post
    Ok I have to ask about min temp for HP.

    Why wouldn't he run the HP down to -5C ? Even at -5C (23F) my HP has COP of 2.4. ( I imagine that his is similar) If his thermal balance point is -5C the HP is still over 2 times more efficient than Electric and cheaper than NG ?
    (Even at -8.5C, my HP produces 23000Btu's )


    Just wondering.

    GC

    Good question. Doesn't make sense to me either. If the heat pump can maintain the temp, it is still operating at a high efficiency. My heat pump has been maintaining house temp down to 17 degrees F so far. COP is still 2.7 or so at that temp. That is still much cheaper than my NG costs.

  8. #8
    Join Date
    Dec 2006
    Location
    Middle Tennessee
    Posts
    11,347

    *

    Quote Originally Posted by badtlc View Post
    Good question. Doesn't make sense to me either. If the heat pump can maintain the temp, it is still operating at a high efficiency. My heat pump has been maintaining house temp down to 17 degrees F so far. COP is still 2.7 or so at that temp. That is still much cheaper than my NG costs.
    my system works fine with heat pump only till outdoor temp drops below 15*

    other systems (sized close) with heat calcs may start needing auxillary heat when outdoor temps drop to 35*

    that being said you should have your system serviced atleast once a year, to maximize performance



    .

  9. #9
    Join Date
    Jan 2004
    Location
    PA
    Posts
    68,776
    Could be caused by several things. Too many to guess over the internet.
    Need a tech to come out and check.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  10. #10
    Join Date
    Jan 2004
    Location
    PA
    Posts
    68,776
    Quote Originally Posted by tclark26 View Post
    heat pumps start to lose efficiency at about 45 degrees fahrenheit so -5 celcius is way too cold for the heat pump to work so your system is compensating by using your auxillary heat to warm your house
    Lots of heat pumps can heat the home to thermostat set point without aux heat at -5°C/23°F.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  11. #11
    Join Date
    Dec 2008
    Posts
    18
    Good evening
    I am experiencing about the same problem with my new Lennox XP14-036 (3 tons),even worst than you!!!!!!!
    I had in the past a 3 tons heat pump with freon R22 which could heat by itself down to -12C !! Now at -2C the Lennox needs the help of my oil furnace!!!!!!! I am very disapointed.......

  12. #12
    Join Date
    Oct 2008
    Posts
    52
    Im not so sure why you are disappointed...heat pumps are set up to give you the highest efficiency. They are set to call for backup heat when they can no longer supply the highest efficiency to you the home owner. Often this is around 30F

  13. #13
    Join Date
    Jan 2004
    Location
    PA
    Posts
    68,776
    Quote Originally Posted by naelec View Post
    Good evening
    I am experiencing about the same problem with my new Lennox XP14-036 (3 tons),even worst than you!!!!!!!
    I had in the past a 3 tons heat pump with freon R22 which could heat by itself down to -12C !! Now at -2C the Lennox needs the help of my oil furnace!!!!!!! I am very disapointed.......
    Not all heat pumps are created equal.

    Some higher SEER have lower heating BTUs then the units they are replacing.

    Some newly installed units, aren't charge right either. Which will also cause them not to be able to heat as well as the old unit did.

    Did you have your contractor recheck the system.
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    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

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