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  1. #1
    Join Date
    Jul 2005
    Location
    Melbourne Fl
    Posts
    39

    McQuay chiller Help

    I have a ALSO70 that keeps tripping out on failed pre purge. I did find drier with a 35 psi differental and replaced them. I still have the same problem of alarming on failed prepurg, any advice thanks

  2. #2
    Join Date
    May 2010
    Location
    Minnesota
    Posts
    20
    Failed prepurg means that the evap pressure did not drop below 40 psi within 45 sec. Check EXV operation and make sure it's closing. you should have 40 ohms at each wire to com. Then make sure driver board is ok. If all that is working then check the compressor itself. You may have gate failure.

  3. #3
    Join Date
    Jul 2005
    Location
    Melbourne Fl
    Posts
    39
    Thanks I will check that tomorrow. It does seem like it will not go below 40 psi on start up, after the third attempt, it will finally start to raise the suction press, but will fail on liquid run. Not to sure on the gates, I did try and close the suction valve after compressor before evap, so that would eliminate the exv not closing, customer did say failing prepurge has been a problem for a while. (still failed pre purge) and compressor has been noisy. Thanks for your reply.

  4. #4
    Join Date
    May 2010
    Location
    Minnesota
    Posts
    20
    No liquid run failures are a result of the high pressure drops(lack of liquid), sounds like this machine has had problems in the past. I would advise you to spend some time with it and check all pressure drops across cond, subcooler, etc. Going over this machine with a fine tooth comb could really be in yours and your customers best interest. Good luck!
    Ty

  5. #5
    Join Date
    Jul 2005
    Location
    Melbourne Fl
    Posts
    39
    Thanks I should have walked away, but my stupid a#$ gets involved. not much info availible except a customer iom manual that is not much help unless i need to know what wire size is needed LOL , just might turn this one over to McQuay services

  6. #6
    Join Date
    Jun 2009
    Location
    Florida
    Posts
    540
    I replied in your other post in commercial. Didn't see this one. Check out what I said there. I think you have a gate rotor problem, especially when you said it was noisy.
    Low Pressure Forever!

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