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  1. #14
    Join Date
    Oct 2004
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    Central WA
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    1,306
    Quote Originally Posted by Warlockamized2 View Post
    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.
    50 degree defrost termination is great for lab testing, but not realistic for the world. We set for 70, and sometimes 90 if there are problems down the road. Wind and other conditions can affect defrost.

    I am also concerned that you refer to the heat pump getting "help" from the furnace. With a dual-fuel setup you should be running heat pump OR furnace, but never both! There should be a set outdoor temperature that determines when the system switches from one to the other.

    It is difficult to determine proper charge in heating, and really needs to be double checked on a warm day with cooling running.

  2. #15
    Join Date
    Nov 2004
    Location
    SW FL
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    5,987
    Quote Originally Posted by beenthere View Post
    Don't try and include defrost as part of COP. What are the actual factory COP ratings at 47 and 17.
    COP is noted on Thermal Balance Point Chart on Left (Compressor Only per Lennox data).
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    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

  3. #16
    Join Date
    Jan 2004
    Location
    Lancaster PA
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    66,750
    Quote Originally Posted by Warlockamized2 View Post
    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.
    Pretty sure thats an on demand defrost board. Which means it won't defrost needlessly. Should put your 17 degree outdoor temp COP including defrost at 2.8 give or take .05 at a 70 degree defrost termination.

    At 50 degree defrost termination, its going into defrost more often then it should since its not completely defrosting. And the COP including defrost will be less then you think.



    PS: Thanks Dan for the PDFs.
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  4. #17
    Join Date
    Dec 2008
    Location
    Ontario Canada
    Posts
    534
    I sounds like there may be a communication breakdown. Is there a chance the OP is confusing defrost termination temp with balance point? And thinks that by raising the term temp he will never run on HP?

  5. #18
    Join Date
    Nov 2004
    Location
    SW FL
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    5,987
    Quote Originally Posted by beenthere View Post
    Pretty sure thats an on demand defrost board. Which means it won't defrost needlessly. Should put your 17 degree outdoor temp COP including defrost at 2.8 give or take .05 at a 70 degree defrost termination.

    At 50 degree defrost termination, its going into defrost more often then it should since its not completely defrosting. And the COP including defrost will be less then you think.

    PS: Thanks Dan for the PDFs.
    I worked these about 2+ weeks ago WITH the OP.

    He has a great system now, the path to Best system performance needs to be defined.

    I can't help on providing proper defrost mode recommendations other than presenting
    THE SPECIFIC Lennox extended performance data.
    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

  6. #19
    Join Date
    Jan 2004
    Location
    Lancaster PA
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    Quote Originally Posted by dan sw fl View Post
    I worked these about 2+ weeks ago WITH the OP.

    He has a great system now, the path to Best system performance needs to be defined.

    I can't help on providing proper defrost mode recommendations other than presenting
    THE SPECIFIC Lennox extended performance data.
    In my area, very few if any on demand defrost units defrost completely at 50 degrees termination(above 38 they do). They tend to build up ice inside the outdoor on the lower 4 to 10 inches of the coil. Which isn't something that the spec sheets can tell you. And once that ice is there, it lowers the outdoor coil temp and then tends to put them in defrost more often. So you can actually lose twice. Less heat output, and more defrost cycles.

    I had to learn this the hard way.
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  7. #20
    Join Date
    Jan 2013
    Location
    sterling heights Michigan
    Posts
    26
    No.I do know the diffrence. Thanks for trying to help.O
    Quote Originally Posted by LKJoel View Post
    I sounds like there may be a communication breakdown. Is there a chance the OP is confusing defrost termination temp with balance point? And thinks that by raising the term temp he will never run on HP?

  8. #21
    Join Date
    Jan 2013
    Location
    sterling heights Michigan
    Posts
    26
    This is very helpful. I can set the defrost temp @ the icomfort wi-fi stat.Sounds like I should try a low set point of someware near 33 F and a defrost temp of 60 F , if I end up using the interuptable electric rate.Low set point will have to be calculated with new defrost temp setting. I think I should ask them to raise the HP above the posable snow level , when they show-up in 2 hours.
    Quote Originally Posted by beenthere View Post
    In my area, very few if any on demand defrost units defrost completely at 50 degrees termination(above 38 they do). They tend to build up ice inside the outdoor on the lower 4 to 10 inches of the coil. Which isn't something that the spec sheets can tell you. And once that ice is there, it lowers the outdoor coil temp and then tends to put them in defrost more often. So you can actually lose twice. Less heat output, and more defrost cycles.

    I had to learn this the hard way.

  9. #22
    Join Date
    Jan 2013
    Location
    sterling heights Michigan
    Posts
    26
    The COP s that I listed here in your quote of mine are from Lennox and reflect defrost @ 50F and all motors and controls.
    Quote Originally Posted by beenthere View Post
    Pretty sure thats an on demand defrost board. Which means it won't defrost needlessly. Should put your 17 degree outdoor temp COP including defrost at 2.8 give or take .05 at a 70 degree defrost termination.

    At 50 degree defrost termination, its going into defrost more often then it should since its not completely defrosting. And the COP including defrost will be less then you think.



    PS: Thanks Dan for the PDFs.

  10. #23
    Join Date
    Jan 2013
    Location
    sterling heights Michigan
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    26
    Quote Originally Posted by dan sw fl View Post
    COP is noted on Thermal Balance Point Chart on Left (Compressor Only per Lennox data).
    Dan where is this attachment data from? Some of this doesn't match the figures I found from Lennox.

  11. #24
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    Jan 2004
    Location
    Lancaster PA
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    66,750
    Quote Originally Posted by Warlockamized2 View Post
    This is very helpful. I can set the defrost temp @ the icomfort wi-fi stat.Sounds like I should try a low set point of someware near 33 F and a defrost temp of 60 F , if I end up using the interuptable electric rate.Low set point will have to be calculated with new defrost temp setting. I think I should ask them to raise the HP above the posable snow level , when they show-up in 2 hours.
    Skip 60, and go right to 70. On demand defrost will allow a fair amount of frost to build up before going into defrost. Low termination temps don't save anything in cold areas. Specially if your in an area that can have high outdoor humidity in the winter.
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  12. #25
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    Nov 2004
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    SW FL
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    Quote Originally Posted by Warlockamized2 View Post
    Dan where is this attachment data from? Some of this doesn't match the figures I found from Lennox.
    Determine C.O.P. = Heat out / Power in { convert 'power in' to btu/hr = watts *3.412}
    as provided on LENNOX catalog page 661 that was e-mailed 2 weeks ago.
    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

  13. #26
    Join Date
    Dec 2007
    Posts
    4,574
    That defrost board has some less than stellar performance, in my opinion.
    I finally learned the other day, completely by accident as I do not see it in any literature, that below 20 it goes into settler every 1/2 hour no matter what!!

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