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Thread: Walk in Freezer

  1. #1

    Walk in Freezer

    Went to a walk in freezer that had stopped working a couple days ago. Found that the high pressure cut out had been tripped. Tried to reset it but I couldn't reset it. So I put a jumper in and checked pressures. HPC was set at 350 and head pressure was 375. Outside ambient was 105. Also found that the fan/defrost temp sensor have some how come apart. So I wired the evap fans to direct power so the fans would run all the time. Got the freezer down to 28 deg

    Today I replaced the dual LPC/HPC and the fan/defrost sensor. Reset the defrost timer and got it going. Had it down to 24 deg in about a half hour.

    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.

    I have never come across this before and wondered if anyone here had any ideas.

    Thanks Jeff

  2. #2
    Join Date
    Apr 2012
    Location
    Jackson, MS
    Posts
    33
    What kind of refrigerant and what temp r u trying to hold. Did u have gauges on and if so how for down did it pump when u pumped down. What kind of compressor is it also.

  3. #3
    What kind of refrigerant I think it was 22. Couldn't read label

    what temp r u trying to hold. 0

    Did u have gauges on and if so how for down did it pump when u pumped down.

    When it pumped down suction went to 0 and liquid was close to 375


    What kind of compressor is it also. Scroll[/QUOTE]

  4. #4
    Join Date
    Oct 2011
    Location
    Chicagoland Area
    Posts
    4,577
    So the compressor won't pump down to zero? Why won't it pump dowm? Bad pump? Capacity? You couldn't find any specs on what the control should be set at? Unless it's being used to control the box temp, there are some pretty standard settings. If you're storing anything but ice in the freezer, 24 degrees is way too high. If the defrost termination switch was shorted, I can almost guarantee there are other issues which you will or will not find when you go back and the coil is frozen.
    Officially, Down for the count

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

    I know enough to know, I don't know enough
    Liberalism-Ideas so good they mandate them

  5. #5
    Join Date
    May 2009
    Location
    The Pas, Manitoba Canada
    Posts
    212
    Pump down system should pull down to 0 psi easily when LLS is deenergized.
    Check suction pressure with suction valve closed to make sure the compressor can pull down. Close LPC or jumper contacts. Then watch suction pressure with compressor off to see if crankcase pressure changes atall. If it stays put ok. If it climbs there's compressor valve problems.

  6. #6
    Join Date
    Oct 2011
    Location
    Chicagoland Area
    Posts
    4,577
    Scroll probably has an internal relief so the pressure will jump once deenergized
    Officially, Down for the count

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

    I know enough to know, I don't know enough
    Liberalism-Ideas so good they mandate them

  7. #7
    Quote Originally Posted by 2sac View Post
    So the compressor won't pump down to zero? Why won't it pump dowm? Bad pump? Capacity? You couldn't find any specs on what the control should be set at? Unless it's being used to control the box temp, there are some pretty standard settings. If you're storing anything but ice in the freezer, 24 degrees is way too high. If the defrost termination switch was shorted, I can almost guarantee there are other issues which you will or will not find when you go back and the coil is frozen.
    The compressor will pump down to zero. The problem is that the LPC is set at 0 and even though the compressor will pump down it will not shut off.

    The question is that, Why is the LPC set at 0? If the LLV closes and the compressor pumps down to 0 and the LPC is set at 0 and the compressor does not shut off then, Why is the LPC set at zero?

    The LPC is not used to control box temp.

    I already have an idea that the defrost timer is not working correctly and causing some of my problems.

  8. #8
    Join Date
    Apr 2012
    Location
    Jackson, MS
    Posts
    33
    I may be wrong but scrolls are not designed to run below 0psig somebody correct me if but If that is so u can't do a pump down test on a scroll u have to contact the manufacturer to do efficiency test.

  9. #9
    Quote Originally Posted by smjrusche View Post
    I may be wrong but scrolls are not designed to run below 0psig somebody correct me if but If that is so u can't do a pump down test on a scroll u have to contact the manufacturer to do efficiency test.
    I think you are correct and thinking about it I think it is a Recipt

  10. #10
    Join Date
    Apr 2012
    Location
    Jackson, MS
    Posts
    33
    U set the lpc at the setting that u feel as necessary below normal operating pressure to shut down condensing unit unless u r using it for temp control which u r not. In my opinion above 0pig when possible. If u have a ll this will help to keep outside contaminants outside the system and shut it of with a positive peas on it. IMO

  11. #11
    Quote Originally Posted by smjrusche View Post
    U set the lpc at the setting that u feel as necessary below normal operating pressure to shut down condensing unit unless u r using it for temp control which u r not. In my opinion above 0pig when possible. If u have a ll this will help to keep outside contaminants outside the system and shut it of with a positive peas on it. IMO
    Thanks, I think you just cleared it up for me. I really want the LPC set as low as possible so that when the LLS closes it removes as much refrigerant as possible and still shuts of the compressor.

    Am I thinking right?

  12. #12
    Join Date
    May 2009
    Location
    The Pas, Manitoba Canada
    Posts
    212
    Is there a contactor for the compressor?

  13. #13
    Quote Originally Posted by K_Neil View Post
    Is there a contactor for the compressor?
    No, Defrost timer

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