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  1. #1
    Join Date
    Nov 2011
    Location
    St. Louis
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    3,635

    Bypassing Hi/Low pressure cut offs

    We should all know better when it comes to bypassing safety switches in heat except for on site diagnostics. Or motor overloads.

    What about high and low pressure cut offs in cooling when the accompanying pressures are normal and the cut offs are tripping?

    I guess another way to pose the question would be this: Is there any condition that would trip a cut off that you would not be able to detect by system pressures?


    Appreciate any consideration,

    h

  2. #2
    Join Date
    Apr 2006
    Posts
    329
    It's tempting to do but I don't think it's worth jumping one out. I don't like to have "what if's" bouncing around my head when I'm home. Things could look ok when you're there, but anything can happen. Say you jump out the the pressure switch that's open even though the systems running @ 250. Then you leave, and the condenser fan dies. Uh-oh. Not worth the risk.

  3. #3
    Join Date
    Nov 2011
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    St. Louis
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    Quote Originally Posted by dudeabides View Post
    It's tempting to do but I don't think it's worth jumping one out. I don't like to have "what if's" bouncing around my head when I'm home. Things could look ok when you're there, but anything can happen. Say you jump out the the pressure switch that's open even though the systems running @ 250. Then you leave, and the condenser fan dies. Uh-oh. Not worth the risk.
    Good point.

  4. #4
    Join Date
    Feb 2012
    Location
    Upstate SC
    Posts
    84
    They sell low end equipment without those safety switches, but I agree with the other posters. You need to restore the customer's equipment to its normal working condition. I have done it to give some temporary relief until I could I could get back and do it right.

  5. #5
    Join Date
    Oct 2005
    Location
    B.C. Canada
    Posts
    903
    really, whats the worst thing that could happen..comp will trip overload or the breaker...worse case your comp will plow the internall relief or if its a bigger system blow the relief and there goes a few hundred lbs.....doubt its gonna hurt anyone not like jumpin a limit on a gas fired appliance
    still not reccomended by me, but i doubt its gonna hurt anyone

  6. #6
    Join Date
    Feb 2012
    Location
    Nebraska
    Posts
    197
    Quote Originally Posted by dudeabides View Post
    It's tempting to do but I don't think it's worth jumping one out. I don't like to have "what if's" bouncing around my head when I'm home. Things could look ok when you're there, but anything can happen. Say you jump out the the pressure switch that's open even though the systems running @ 250. Then you leave, and the condenser fan dies. Uh-oh. Not worth the risk.
    I found one like this yesterday. Tripping on high pressure. Freon charge looked great. Amp draw was 1.6 on condensor fan motor rated at .9. Cap was good. Motor coming in Monday.

  7. #7
    Join Date
    Nov 2011
    Location
    St. Louis
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    Quote Originally Posted by ORV View Post
    I found one like this yesterday. Tripping on high pressure. Freon charge looked great. Amp draw was 1.6 on condensor fan motor rated at .9. Cap was good. Motor coming in Monday.
    CF motor failing and the high side wasn't elevated?

  8. #8
    Join Date
    Nov 2006
    Location
    Southeastern Pa
    Posts
    19,496
    Yesterday, I had my first "no ac" call of the season.

    Compressor not running. Good standing pressure, but low side cutout open.
    I jumped it out just long enough to find out why it failed. Poor aiflow has been causing the unit to cycle on the switch, until it gave up. In commercial, we quote all proposed repairs first, a process that takes an aproval from the store corporate.

    Leaving that switch out and running the unit would not have been a professional repair.
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  9. #9
    Join Date
    Jul 2007
    Location
    Mount Airy, MD
    Posts
    7,281
    How long does it take to add a tee and another switch anyways? What about 10 minutes? The cost for equals? not much.....

  10. #10
    Join Date
    Jul 2006
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    Anytown USA
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    Quote Originally Posted by timebuilder View Post
    Leaving that switch out and running the unit would not have been a professional repair.
    Bypassing the switch and giving them cooling also gives the cheap customers a reason not to replace the switch, because its "working" now..

  11. #11
    Join Date
    Nov 2011
    Location
    St. Louis
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    Quote Originally Posted by Chris_Worthington View Post
    How long does it take to add a tee and another switch anyways? What about 10 minutes? The cost for equals? not much.....
    In case you are after hours and didn't have one on the truck.

    May I ask what "tee" you refer to? I thought it was a simple matter of a threaded/schrader fitting?

  12. #12
    Join Date
    Jul 2007
    Location
    Mount Airy, MD
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    7,281
    Quote Originally Posted by hurtinhvac View Post
    In case you are after hours and didn't have one on the truck.

    May I ask what "tee" you refer to? I thought it was a simple matter of a threaded/schrader fitting?
    Assuming the old has no schrader core, add an access tee with a core depressor, attach switch and call it done

    As others have said that is a call you need to make, supply houses are generally open the next day here

  13. #13
    Join Date
    Mar 2007
    Location
    NW AR
    Posts
    2,478
    Quote Originally Posted by hurtinhvac View Post
    In case you are after hours and didn't have one on the truck.

    May I ask what "tee" you refer to? I thought it was a simple matter of a threaded/schrader fitting?
    Adding a tee to the low or high side will allow you to add a new pressure switch without losing or having to recover any refrigerant.

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