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Thread: McQuay screw

  1. #1
    Join Date
    Aug 2009
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    minnesota
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    17

    McQuay screw

    Have a problem with a mcquay screw chiller the diagnostic is no evap pres drop any thoughts out there, or has anybody seen this problem?

  2. #2
    Join Date
    Feb 2003
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    Wichita Ks
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    1,477
    Is it a ALS? It means the compressor is not pumping. Check the breaker for compressor, the little black relay could be bad for that compressor. If it has soft start check to see if it is in alarm. Compressor could be shelled out.

  3. #3
    Join Date
    Aug 2009
    Location
    minnesota
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    it is an intermintent problem could the exv be stuck open?

  4. #4
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    Feb 2003
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    Wichita Ks
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    if it was stuck open the compressor would still pump, if it only does it once in a while swap the relay with the alarm relay and see if problem goes away. if your expansion valve is stuck open you better replace it.

  5. #5
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    minnesota
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    wich relay are you talking about that could be bad

  6. #6
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    Feb 2003
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    I assume you have a ALS chiller. What is your model number? If it is a ALS it would be the relay for that compressor. IT should be labeled. The ALS has a relay board with a bunch of black relays, they are replaceable. Also the ribbon cable should be checked.

  7. #7
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    Aug 2009
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    minnesota
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    yes it is an ALS chiller i will look at the relay on monday thanks.

  8. #8
    Join Date
    Jun 2009
    Location
    Florida
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    540
    Quote Originally Posted by chillertech257 View Post
    yes it is an ALS chiller i will look at the relay on monday thanks.
    Isolate the compressor and recover the pressure from it, then pull the gate rotor inspection cover and check the condition of the rotor liners or inserts or whatever they are called. They should not be pitted and the edges should be sharp and not rounded off. Has that circuit ever had a compressor failure prior to this event?
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  9. #9
    Join Date
    Aug 2009
    Location
    minnesota
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    don't know fri was the first time the customer let me look at this chiller has had another contractor trying to fix this problem for more than 2 years. I take care of all his other chillers so he wanted me to look into this one and see if i can get it fixed.

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