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  1. #1
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    May 2020
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    Hmm McQuay AGS320 chiller short run time

    We have been asked to work on this AGS320 chiller. It's 13 years old and I think it has a lot of unknown repair. We are new to the McQuay air cooled chillers. We sent our mechanic to the Daikin class in Virginia.We found 5 dead EXV control boards along with 2 EXVs in the control cabinet. The biggest problem we have is that it runs for 10 minutes then shuts off. No alarms. It's off for 10 minutes and starts back up. Both circuits do the same thing. During that time we noticed neither compressor loads up. If we manually run the slide open it cools respectably. We can't get it to run any longer than that to help it settle down. The subcooling is less than 22 required by the instructions. We added some refrigerant but are hesitant adding any more until we can get it to run for longer times. Are we not meeting some operating conditions that makes it have a short run time? Tech support doesn't know why it does this. They say add more refrigerant. Discharge and suction super heat show 0. Subcooling is not coming up past 12 after 100+ lbs of refrigerant. Kinda stumped here.

  2. #2
    Join Date
    Nov 2011
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    CO
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    it's just an air conditioner......

    pull and weigh the charge, so it can be eliminated as a possible cause, then move on.

    support has told you to add more, start with that (pull and weigh) so you know 100% what you've got in it....otherwise, you're just guessing.

  3. #3
    Join Date
    Apr 2020
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    va
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    AGS320-A,B,C or D? A& B have flooded evaporators, C dx 3200 only compressor, D 3200 or F4 compressor, no optical sensors....
    AGS A& B are critical charge (pia) and oil management is more sensitive.

    Must know flow rate, start delta T, stage up setting, stage down setting, evaporator approach, setpoint.
    Hours/starts ratio are a good indicator of poor set-up.

    The units have anticipatory warnings that should be reviewed along with the alarm history.

    A good complete log sheet along with the controller settings should tell you what you need.

  4. #4
    Join Date
    Sep 2008
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    Sunrise,fl
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    Dsh should be above 25

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