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Thread: Walk in Freezer

  1. #14
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    Oct 2011
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    Dumb question. Are you sure the high side cap tube is hooked up to the high side and the low side hooked up to the low side? If the low side cap tube is hooked up to the high side the switch will never open.
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  2. #15
    Join Date
    Jun 2012
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    37
    The whole point of a pump down system is to get all the liquid out of the evap and prevent refrigerant migration to the compressor during the off cycle. I usually shoot for around 5psig and set a differential of about 15 to 20 (cut in at 20-25). I don't usually trust the pressure scale on the switch, I don't think they are very accurate. I set it with my what pressure my gages are reading. And if you don't have a contactor that controls the compressor then I would consider putting one on there unless your pressure switches and whatever else is controlling the compressor are rated at 30 amps or better.

  3. #16
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    Jun 2012
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    Also you don't want your low pressure cut out below 0psig in case a leak develops on the low side. You would suck air/moisture in the system every time it pumps down.

  4. #17
    Join Date
    Sep 2007
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    State College, PA
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    Quote Originally Posted by Flip14 View Post
    Also you don't want your low pressure cut out below 0psig in case a leak develops on the low side. You would suck air/moisture in the system every time it pumps down.
    You would only suck in air/moisture if there was a leak.
    Can someone please explain to me -
    Why is there never enough time to do it right the first time, but plenty of time to do it twice?


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  5. #18
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    Sep 2007
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    Quote Originally Posted by 2sac View Post
    Dumb question. Are you sure the high side cap tube is hooked up to the high side and the low side hooked up to the low side? If the low side cap tube is hooked up to the high side the switch will never open.
    This makes the most sense at to what is going on.

    Also, it is hard to believe there is no contactor controlling the compressor.
    Can someone please explain to me -
    Why is there never enough time to do it right the first time, but plenty of time to do it twice?


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  6. #19
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    Jun 2012
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    Quote Originally Posted by joemach View Post
    You would only suck in air/moisture if there was a leak.
    Hence the reason I said "in case a leak develops on the low side".

  7. #20
    Join Date
    May 2010
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    1,291
    Ya, I hope you are not pumping a scroll down to 0PSI Please do yourself a favor and call a pro or for help. If it is a scroll, you could be doing damage to the compressor.

    You not having a contactor is another issue. You need to have one!

    This thread gets weirder by the second lol

  8. #21
    Quote Originally Posted by ZeroTolerance View Post
    Ya, I hope you are not pumping a scroll down to 0PSI Please do yourself a favor and call a pro or for help. If it is a scroll, you could be doing damage to the compressor.

    You not having a contactor is another issue. You need to have one!

    This thread gets weirder by the second lol
    This is my original question which no one has answered

    My problem is this when I replaced the LPC/HPC the low pressure cut out was set at 0 and when the system went into defrost and the LLS closed the condenser would still run. I couldn't find any specs on what the LPC should be set at. I set it at 25.

    So, if it pumps down to zero and the LPC is set at zero and the compressor still run....might be a problem?

    I am a pro by the way Zero and was just asking questions. I thought this was the place for pro to converse. It has no contactor but as I stated before it has a defrost timer or a clock timer.

    I called the manufacture and the LPC should be set at 10. I also have discovered that last week with 110-115 outside temp the local electric company had to use back up generators and have had some voltage spikes. Voltages had at time dropped below 200 vac. So, I have also concluded that a voltage spike has damaged the contacts in the timer. Replace the timer today and the box temp has been at 13 degree all day.

  9. #22
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    You set it at 25? 25 what? Mfg says 10. You need a cut in and cut out. You concluded a voltage spike damaged the timer. That may be true but I'd bet the shorted termination switch is what damaged it. The pro's section is the place for pro's to converse. There is no DIY so our advice is limited in the open forums. Build up your post count and apply for pro membership.
    Officially, Down for the count

    YOU HAVE TO GET OFF YOUR ASS TO GET ON YOUR FEET

    It was working when I left...
    Liberalism-Ideas so good they mandate them

  10. #23
    Join Date
    May 2011
    Location
    Spring City, Pennsylvania, United States
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    181
    The real way to set a pump down system is to make sure that your pumpdown psi converted to saturated temp is lower than the lowest ambient temp your condenser will see. Imo... Also did you set your new lpc with nitrogen first, they are seldom 100% accurate but these are just my 2 cents

  11. #24
    Join Date
    Jun 2012
    Posts
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    If the mfg said 10 then I would set it at 10. I usually shoot for 5psig for the cut out, gives me a good buffer to make sure I don't hit 0psig. I set the differential at 15-20 (cut in 20-20psig).

  12. #25
    Join Date
    Feb 2008
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    California
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    Quote Originally Posted by smythers1968 View Post
    My problem is this when I replaced the LPC/HPC the low pressure cut out was set at 0 and when the system went into defrost and the LLS closed the condenser would still run.

    You either have

    LLS bleeding through (did you verify actual suction pressure lowering to LPC C/O setpoint during pump down?)

    Faulty control

    You hooked up the pressure lines wrong

    You have a wiring error


  13. #26
    Join Date
    Apr 2010
    Location
    Central Minnesota
    Posts
    18
    I had a faulty bypass timer do this to me once. Its a time delay relay that bypasses the LPC for a set amount of time for low ambient starts. The timer never opened its contact after time had elapsed, constantly running the compressor after pumpdown.

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