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  1. #1
    Join Date
    Jan 2013
    Location
    sterling heights Michigan
    Posts
    26

    Lennox XP21 heatpump has 6"-8" of ice not removed by defrost mode

    The heat pump when first installed at the end of December would heat the house by its-self without much if any help from the furnace with an outside temp of 15 to 24 F . Now it has to have help from the furnace most of the time at a 31 F outside temp. When I noticed this I went outside to look at the coils and found what looks like 6 " to 8" of ice built up inside the unit coils and all. Could a low charge cause this ? 4 ton unit with a 5 ton coil , both from Lennox. Heated charge not getting to lower coils because of a low charge? When installed it was under charged. A few weeks after installation it had more refrigerant put in. Charge was never checked with "super heat/cool," the charge was only done by weighing refrigerant. Low charge or should the defrost setting be moved up from 50F. The rest of the coil is free of ice it is just the very bottom 6" that is solid ice. Lennox furnace model #SLP98UH110XV60C Lennox cased coil model # CX34-62C Lennox heat pump model # XP21-048-230 Lennox comfort wi-fi touch. Once the electric meter is installed I will use a low setpoint of about 33 - 35F.

  2. #2
    Join Date
    May 2009
    Location
    Savannah, Ga/H.H. Island, S.C.
    Posts
    1,401
    Sounds like you have more than just a thermostat settings issue. Call the installing contractor. The unit should still be under warranty.

  3. #3
    Join Date
    Jan 2013
    Location
    sterling heights Michigan
    Posts
    26
    The contractor will be here friday. I am hopping that someone could shed some insight. I have no issue with the thermostat.That way I may be able to have some suggestion or question for him when he shows friday. Could this ice be normal?

  4. #4
    Join Date
    Jan 2013
    Location
    sterling heights Michigan
    Posts
    26
    It is posable that he resent snow storm of 6" to 8" of snow may have blocked off the first 6" to 8" of coil , allowing that portion of the coil to get the ice on it. The defrost wasn't able to defrost that first 6" to 8" because it was under the snow. Maybe putting some legs on it ( as shown in the installation instructions) will solve the problem. What do you think?

  5. #5
    Join Date
    May 2008
    Location
    Missouri
    Posts
    3,421
    Make sure this HP is up on riser legs. Sounds like the moisture is building up in the lower coils and not running/draining away from the coils. Could damage the lower coil tubing. Call the installation company back. You could also have a leak, in which case the company needs to find it and fix it, period. This is WAY too new a unit to be be having these issues!

  6. #6
    Join Date
    Jan 2013
    Location
    sterling heights Michigan
    Posts
    26
    I hope they wont want to just rise the defrost temp ,that will kill the efficiency.

  7. #7
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,712
    50 is a bit low for defrost termination.
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  8. #8
    Join Date
    Dec 2007
    Posts
    4,668
    among other things, sounds like the installer may be questionable.

    defrost temp needs to be higher, that 50 is factory setting, for your climate, say 70 minimum and possibly 90.

    the unit must be up off the ground or base it is sitting on. it needs to be able to defrost and have the water go someplace other than refreeze on the unit and build up.

    instructions are provided for a reason.

    what does this mean, "...Once the electric meter is installed I will use a low setpoint of about 33 - 35F."?

    good luck!!
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  9. #9
    Join Date
    Jan 2013
    Location
    sterling heights Michigan
    Posts
    26
    I think that my electric rate may end up being .09175 per KWH for interruptible service. Gas cost is around .958 per therm.Low set point should be 34 F or 35 F using a 50 F defrost. If the defrost temp is changed I wont know how to refigure the low set point.This may be my only affordable option to run this.
    Quote Originally Posted by pacnw View Post
    among other things, sounds like the installer may be questionable.

    defrost temp needs to be higher, that 50 is factory setting, for your climate, say 70 minimum and possibly 90.

    the unit must be up off the ground or base it is sitting on. it needs to be able to defrost and have the water go someplace other than refreeze on the unit and build up.

    Instructions are provided for a reason.

    What does this mean, "...Once the electric meter is installed I will use a low set-point of about 33 - F 35."?

    good luck!!

  10. #10
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,712
    Quote Originally Posted by Warlockamized2 View Post
    I think that my electric rate may end up being .09175 per KWH for interruptible service. Gas cost is around .958 per therm.Low set point should be 34 F or 35 F using a 50 F defrost. If the defrost temp is changed I wont know how to refigure the low set point.This may be my only affordable option to run this.
    What is your heat pumps COP at 35 degrees outdoor temp.

    At the rates you posted. Your heat pump needs to be at a COP of 2.74 or better to be cheaper then a 97.5% efficient gas furnace.


    PS: If your heat pump isn't completely defrosting with terminal temp set at 50. then your calculations will be off, since you aren't getting full capacity because of the incomplete defrost.
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  11. #11
    Join Date
    Jan 2013
    Location
    sterling heights Michigan
    Posts
    26
    OUTDOOR temp at 47 F dry bulb with a 70 F entering indoor coil gives a COP of 3.1 and includes defrost ect,. Outdoor temp at17F dry bulb with 70 F entering indoor coil gives a COP of 2.38 and includes defrost ect, My best guess of the COP @35F outdoor temp is 2.8 .If the defrost temp is changed from 50 the COP should be lower because it will defrost longer.
    Quote Originally Posted by beenthere View Post
    What is your heat pumps COP at 35 degrees outdoor temp.

    At the rates you posted. Your heat pump needs to be at a COP of 2.74 or better to be cheaper then a 97.5% efficient gas furnace.


    PS: If your heat pump isn't completely defrosting with terminal temp set at 50. then your calculations will be off, since you aren't getting full capacity because of the incomplete defrost.

  12. #12
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,712
    Don't try and include defrost as part of COP. What are the actual factory COP ratings at 47 and 17.
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  13. #13
    Join Date
    Nov 2004
    Location
    SW FL
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    6,234
    Quote Originally Posted by beenthere View Post
    What is your heat pumps COP at 35 degrees outdoor temp.

    At the rates you posted. Your heat pump needs to be at a COP of 2.74 or better to be cheaper then a 97.5% efficient gas furnace.


    PS: If your heat pump isn't completely defrosting with terminal temp set at 50. then your calculations will be off, since you aren't getting full capacity because of the incomplete defrost.
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