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  1. #1
    Join Date
    Aug 2011
    Posts
    11

    Confused Low pressure cut-off switch

    One of my walk-in boxes is controlled by a temp gauge that operates a solenoid to close the liquid line and drop the suction pressure to trip the low pressure cut-off switch. The compressor is external and I did not notice until recently that the cut-off switch was not opening on pressure drop and the compressor was running constantly. The switch is a Texas Instruments PS80-02-F1009 015-005 and the system runs on R22. My supply house has another manufacturer's switch that cuts off at 10psi and cuts back in at 25psi. Will this switch function properly? And can I let the compressor continue to run constantly for another day or two until I replace the switch?
    Any advice will be greatly appreciated. Bobby

  2. #2
    Join Date
    Feb 2006
    Location
    Atlanta,GA.
    Posts
    867
    what was the pressure? maybe you have another problem than the switch,by the way they have adjustable ones so you can set pressure setting where you want

  3. #3
    Join Date
    Oct 2004
    Location
    Central WA
    Posts
    1,471
    The compressor is cooled by the refrigerant running through it. Leaving it run while pumped down is very hard on it.

  4. #4
    Join Date
    Aug 2011
    Posts
    11

    pressures

    The running pressure is about 45 and it drops to almost 0 when the solenoid closes; that's why I'm thinking the 10-25 switch should work.
    The compressor has two fans pulling air across it and I can lay my palm flat on it when it's pumped down and it feels very warm but surprisingly not hot. I have had compressors in some of my reefers run hot enough to fry eggs on and last for years, that's why I thought this one might survive a couple of days. But I'll ask the boss if he wants cold beer at the risk of losing a compressor.

  5. #5
    Join Date
    Oct 2004
    Location
    Central WA
    Posts
    1,471
    If it won't pull below zero it may already be dying.

  6. #6
    Join Date
    Sep 2008
    Location
    Western PA
    Posts
    25,400

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