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  1. #1
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    getting highhead pressor problem with rheem heatpump unit?

    hello techs i was working on a rheem hP-unit M# RHLL-HM3617JA CONDENSING UNIT M#RPNL-036JAZ, I chraged it with R410A,& watched operation in cooling & in heating but in heat mode the headpressor which is the airhandler rises to 600psi & shuts off on safety,in cool mode my lowside stays around 100psi & highside after running 15min slowly rises yes coil is blowen out with co2 so its clean but the compressor amp starts to rise as well,in cool mode i get supply air 47 Return air 67 which sounds like a good split, am trying to understand if its slithly overcharged or some other issue in heatmode by the way it has expanstion vavle by the condensor & evap,i am a pro member i know this is not the rite forum to post but for some reason i cant post on pro fourms any tech out there any suggetion or guide would help,i gave much info i could,thanks

  2. #2
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    First, PLEASE make sentences. Use of punctuation and one thought per sentence will make your posts understandable.

    As far as I can tell, this is the correct forum.

    Now, as to the issue, if you have a microchannel coil indoors you will need to add a mild weather control to reduce the condenser fan speed. The microchannel coil does not have enough capacity to hold all the refrigerant as liquid which causes high head pressure. The first instance of this that I encountered drove me crazy until I spoke to Nordyne tech support and learned that such a device existed. Installing it took care of the problem.
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  4. #3
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    Ask the client if anybody has worked on it before you as they may have added some.You did not say what the outdoor temp was to give an idea where the low side pressure might be. Is the filter dirty?Look for high subcooling in cool mode but you will need to have a warmer indoor temp than 67. subcooling above 12 degrees on this model could indicate an overcharge. You could also recover and weigh in charge to be sure.weigh 1 lb out and see if it stays online.My experience has been if properly charged these HP's will run to the T&P charts printed on the panel pretty well.

    Good luck

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  6. #4
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    Mar 2018
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    if you figure it out please let us know what fixed it. I deal with mostly heatpumps
    Last edited by Pres1227; 04-14-2018 at 04:04 PM. Reason: After review this seems rediculous

  7. #5
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    But I would definantly start with checking the charge more closely before adjusting and valves

  8. #6
    Join Date
    Aug 2014
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    Thread Starter
    Quote Originally Posted by theoldscroll View Post
    Ask the client if anybody has worked on it before you as they may have added some.You did not say what the outdoor temp was to give an idea where the low side pressure might be. Is the filter dirty?Look for high subcooling in cool mode but you will need to have a warmer indoor temp than 67. subcooling above 12 degrees on this model could indicate an overcharge. You could also recover and weigh in charge to be sure.weigh 1 lb out and see if it stays online.My experience has been if properly charged these HP's will run to the T&P charts printed on the panel pretty well.

    Good luck
    thanks for the suggestionswill return to job next week & check it & finalize what happend.

  9. #7
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    Sep 2014
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    Portland, Oregon, United States
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    Sounds grossly over charged bit we still need more info.
    I had what sounds like a similar issue with a Rheem A.C. on start up things were ok, after a few minutes it tried to stabilize and the high side jumped 400 then 500 and 600 all within a matter of 45 seconds or so. Turned out to be double charged. Customer said nobody has ever touched it.... uh huh. Sure.

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  11. #8
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    Quote Originally Posted by nytech28 View Post
    hello techs i was working on a rheem hP-unit M# RHLL-HM3617JA CONDENSING UNIT M#RPNL-036JAZ, I chraged it with R410A,& watched operation in cooling & in heating but in heat mode the headpressor which is the airhandler rises to 600psi & shuts off on safety,in cool mode my lowside stays around 100psi & highside after running 15min slowly rises yes coil is blowen out with co2 so its clean but the compressor amp starts to rise as well,in cool mode i get supply air 47 Return air 67 which sounds like a good split, am trying to understand if its slithly overcharged or some other issue in heatmode by the way it has expanstion vavle by the condensor & evap,i am a pro member i know this is not the rite forum to post but for some reason i cant post on pro fourms any tech out there any suggetion or guide would help,i gave much info i could,thanks
    I see nothing about Air Flow?

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  13. #9
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    Quote Originally Posted by nytech28 View Post
    hello techs i was working on a rheem hP-unit M# RHLL-HM3617JA CONDENSING UNIT M#RPNL-036JAZ, I chraged it with R410A,& watched operation in cooling & in heating but in heat mode the headpressor which is the airhandler rises to 600psi & shuts off on safety,in cool mode my lowside stays around 100psi & highside after running 15min slowly rises yes coil is blowen out with co2 so its clean but the compressor amp starts to rise as well,in cool mode i get supply air 47 Return air 67 which sounds like a good split, am trying to understand if its slithly overcharged or some other issue in heatmode by the way it has expanstion vavle by the condensor & evap,i am a pro member i know this is not the rite forum to post but for some reason i cant post on pro fourms any tech out there any suggetion or guide would help,i gave much info i could,thanks
    The AH is now the condenser in heat mode, do you see any signs of a restriction? frost/ice build up anywhere inside the AH (condenser in heat) ... Dirty air filters? Air flow? Fan working properly?

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  15. #10
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    Quote Originally Posted by pecmsg View Post
    I see nothing about Air Flow?
    I thought that was a given but I guess we should really never assume huh.

  16. #11
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    Quote Originally Posted by nytech28 View Post
    ..in cool mode my lowside stays around 100psi...in cool mode i get supply air 47...
    Those numbers are symptomatic of low indoor airflow...which would make the head pressure go high in heat cycle.

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  18. #12
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    Jun 2017
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    Missouri
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    check your indoor motor speed taps, I'm finding a lot of them that aren't adjusted at installation

  19. #13
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    Dec 2016
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    Possible that the condenser and evaporation coil don't match, 100psi suction in cooling if you worked fine enough in cooling it's probably not airflow related but static pressures and the manufactures CFM chart to make sure you're moving the proper airflow as mentioned above.

    If cooling works well enough and your trouble is only with heating I would be concerned for a possible TXV failure in the outdoor unit causing the high pressures in heating, but that would only be a thought after testing airflow.

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