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  1. #1
    Join Date
    Jun 2012
    Location
    Pittsburgh PA
    Posts
    57

    a/c problem everythings running but need help

    Call started off a bad compacitor then i noticed they hadnt changed there spacegaurd for a while. Got unit up and runnning and told them to leave off till i got filter next day. Replaced filter unit was running hot
    Amana Rcb30c2b 10/11 seer 2.5 ton furn and a/c installed in 2004
    Suc;85 @90 outside temp
    Dis; 350
    I Cleaned condenser which didnt seem dirty and pressures didnt change from it, also pressues and temps were fluctuating. I then reclaimed refrigerant and left nitrogen overnite

    Today i was there and i took apart piston(correct size pistion) and blew everything out evacuated and recharged unit to be sure there wasnt air in the system.
    95 outside
    79 R/A temp 67 WB
    68 supply air temp Keep in mind i didnt want to charge anymore with high head pressure fluxuating from 295-325
    At 310psi 135st 115 line temp at condenser
    70psi 42st 71 line temp at condenser
    keep in mind my pressure and tempature readings were fluxuating as i was taking them.
    Pressures should be @250 and 80 from the data sheet from unit

  2. #2
    Join Date
    Apr 2012
    Location
    lexington, NC
    Posts
    32
    I have seen lower seer units run higher head pressures in extreme heat due to smaller coil surface area. I always charge using superheat if I have a piston system. IMO you need to add gas.

  3. #3
    Join Date
    Jun 2012
    Location
    Pittsburgh PA
    Posts
    57
    What about the pressures fluctuating?
    the pressures both are going up and down along with my line temps ?

  4. #4
    Join Date
    Jun 2012
    Location
    Pittsburgh PA
    Posts
    57
    Anyone know a list of things that would cause the fluctuating of pressures and temps
    I thought non condesables,air, moisture
    condenser recirculation?
    condenser fan not functioning 100% (how to know)
    also is a 2-3 degree difference ok on a liquid line drier?

  5. #5
    Join Date
    Jun 2004
    Posts
    863
    High subcool
    High superheat

    You have restriction.

    2-3 diff is not ok on drier

    Is that a new drier?

  6. #6
    Join Date
    Jun 2004
    Posts
    863
    Brad did you happen to add refrigerant
    When you got there?
    Because it look like it was low ?

    A restricted drier will simulate the system being low
    Did you add gas to reach 85 psi?

    Restricted drier can make it fluctuate
    That also mean that your system is already overcharge.

    A drier should not have any temp diff across it.
    Check drier by pressure drop
    No more than 2 psi across.

    Also u ask how would you know if the motor is functioning 100?
    If the motor is not functioning 100 percent, it will probably be
    Over amping and overheat

    Good luck and let us know

  7. #7
    Join Date
    May 2007
    Location
    Canada
    Posts
    90
    I get why you wouldn't want a temp or pressure difference across a drier but how do you check pressure drop across a drier?

  8. #8
    Join Date
    Jun 2012
    Location
    Pittsburgh PA
    Posts
    57
    when i got there i didnt add any refrigerant It was running at 85/350 then i cleaned condenser and no difference. Although both pressures and line temps were fluctuating.
    My superheat and subcooling were moving around. (fixed md). I figured air in system and let sit overnite with nitrogen. Next day i evacuated and recharched but my pressures and tempatures were moving around still. The liquid line drier is inside the condenser my temp across was 2.5 although the two probes tend to differ within a degree. I wanted to change the drier but i dint have one at the time. Pressure are fluctuating about 30psi on high side and about 10 psi on the low side so hard to say what my sh and sc reading are

  9. #9
    Join Date
    Jun 2012
    Location
    Pittsburgh PA
    Posts
    57
    I just checked the tempature across not sure aboout the psi unless you have a port there to check it

  10. #10
    Join Date
    Jun 2004
    Posts
    863
    Brad I would start by changing drier.
    Bad news is you have to recover again
    Install new drier outside of condenser instead

  11. #11
    Join Date
    Jan 2005
    Location
    Houston TX
    Posts
    875

    Residential system

    Brad gall- Was your pressure temperature true, even though it may have been high. The fluctuation your may be seeing is hydraulic action through your liquid line drier. I would pump it down or remove the charge and change out he drier, go to the next size larger drier in cubic inch capacity. Verify there is no drier inside the condensing unit as most manufacturers put a bullet drier inside the unit. What I meant by true was did you pressure temperature match or was it way out of wack, this would mean non-condensibles. If pressure and temps were fairly close you are overcharged with a restriction, your drier.-GEO
    Once in a while everything falls into place and I am able to move forward, most of the time it just falls all over the place and I can't go anywhere-GEO

  12. #12
    Join Date
    Jun 2012
    Location
    Pittsburgh PA
    Posts
    57
    Quote Originally Posted by shaka View Post
    Brad I would start by changing drier.
    Bad news is you have to recover again
    Install new drier outside of condenser instead
    Im going to and already should have Thanks so much ill let you know how it goes

  13. #13
    Join Date
    Jun 2012
    Location
    Pittsburgh PA
    Posts
    57
    ga1279 Im going to change the drier out and yes my pressures were moving around alot which intern was changing my temp. reading as they moved around so did my temps

    Thanks alot i really appreciate all the help on here since im newer to the sercive end of the business

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