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  1. #27
    Join Date
    Jan 2013
    Posts
    4
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    Quote Originally Posted by Milk man View Post
    The head pressure will sky rocket with an undersized coil on a Lennox heat pump. The only way to match an indoor coil with a Lennox heat pump is with the engineering data.
    Correct to properly match you need to match the coil but the unit is tripping head pressure almost instantly. Mismatched coil would take longer to trip.

  2. #28
    Join Date
    Nov 2001
    Location
    east kansas
    Posts
    8,046
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    Right. Unless it's overcharge to begin with. It's been a while since I've seen an undersized coil. I think it took about three minute of run time with the pressures slowly raising then only a minute or two to hit the high pressure switch.

    First step has already been mentioned. Pull some gas so it will run and the diagnostic reading can be captured. Then the guessing can stop and the fixing can begin.
    Beware of advice given by some guy on the Internet.

  3. #29
    Join Date
    Nov 2014
    Posts
    7
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    Hi there new member. I am working on a lennox heat pump with the same exact problem. I was wondering was it the indoor or outdoor txv that caused the high head? Thanks guys

  4. #30
    Join Date
    Jul 2006
    Location
    Virginia
    Posts
    5,036
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    i find that if the outdoor txv is bad it wont make enough heat to run up the discharge pressure ,high discharge pressure is most likely either lw airflow or overcharge

  5. #31
    Join Date
    Nov 2014
    Posts
    7
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    It's a little Strange. The homeowner says he has been reseting the hps once every two or three days in cooling. Now in heating it runs for about a minute and trips out at 400 psi.

  6. #32
    Join Date
    Jul 2006
    Location
    Virginia
    Posts
    5,036
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    nothing strange about a overcharge condition

  7. #33
    Join Date
    Nov 2014
    Posts
    7
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    Thank you. I will pull it out and weigh it back in to correct the pressures

  8. #34
    Join Date
    Jul 2013
    Posts
    44
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    overcharge , if the outdoor txv is bad it would pump down , get the charge right!

  9. #35
    Join Date
    Nov 2014
    Posts
    7
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    Thank you for the help

  10. #36
    Join Date
    Jul 2012
    Posts
    1,355
    Post Likes
    overcharged or clogged/ stuck closed outdoor txv is my guess.

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