Results 1 to 11 of 11
  1. #1
    Join Date
    Apr 2012
    Posts
    14

    Low side pressure too low high side pressure too high

    Hello everyone, new to the industry and work for a school district so here I am. Pretty much all the equipment I work on is 40yrs old or older. Anyway got a call for a pass through refrigerator not keeping temperature. Temps in the box were @ 75 deg. Compressor was going, hooked up guages and found the pressures all whacked out. Low side was @ 8psi and high side @ 340psi. Compressor was really hot. My first guess was bad tx valve. Don't want to just be a parts changer. R12 system was retrofitted with 401A back in 2002. Just want to be pointed in the right direction. Any help would be greatly appreciated.
    Thank You in advanced,
    Frank

  2. #2
    Join Date
    Oct 2011
    Location
    Chicagoland Area
    Posts
    4,698
    You're on the right track. Get your SH and SC redings and make sure the coil is clean.
    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

  3. #3
    Join Date
    Apr 2012
    Posts
    14
    Ok, great thx. I will have to expose the coil (quite the task) and check super heat. Thanks for the info,
    Frank

  4. #4
    Join Date
    Jun 2012
    Posts
    37
    I agree with 2sac, you probably do need to clean the coil. Your head pressure is WAY too high. With the info you gave it could be a restriction and the unit could be overcharged trying to compensate for the restriction. But once you get your subcool and superheat that will give you a better idea if that could be the problem.

  5. #5
    Join Date
    Jun 2012
    Posts
    19
    If I have a unit I am not familiar with and I am not certain of the issue, I like to recover and charge to weight, at least that way I know what I am working with.

  6. #6
    Join Date
    Dec 2004
    Location
    Chicago area
    Posts
    1,439
    Quote Originally Posted by Aalmaraz View Post
    If I have a unit I am not familiar with and I am not certain of the issue, I like to recover and charge to weight, at least that way I know what I am working with.
    On smaller systems and ice machines, this is the only way to go.

  7. #7
    Join Date
    Aug 2009
    Location
    Peoria IL
    Posts
    72
    You said school whats the room temp ac turned off for the summer, clean the coil, get sh sc and i agree sounds like a restriction, careful on the wiegh in its a conversion from r12 to 401 "mp39" the mfg tag will be wrong

    Make sure both coils are clear and fans are running, good luck lets us know

  8. #8
    Join Date
    Apr 2012
    Posts
    14
    ok, finally got around to this unit. I recovered all of the refrigerant and blew out the lines, evap was actually pretty clean. Replaced the drier and pulled a vacuum. Charged the system and all is well. As figured, there was a restriction in the system. Thanks to all for the input

  9. #9
    Join Date
    Aug 2012
    Posts
    7
    Quote Originally Posted by heatingman View Post
    On smaller systems and ice machines, this is the only way to go.
    Amen! Never know what the guy before you has done.

  10. #10
    By reading what he has said the symptoms are , I believe the system had non condensibles in the system and by recovering gas evacuating and charging with new gas he has rectified the problem

  11. #11
    Join Date
    Nov 2006
    Location
    Southeastern Pa
    Posts
    18,855
    Our Co has taken on more restaurant refrigeration work in the past month. If there is one commonality to these calls, it is the work of the previous Co.

    By cleaning the condensers, recovering the charge, and weighing in to nameplate, we are fixing 90% of the failures.

    My boss suggested using the Fume Free Easy Off oven cleaner on the condensers, because they were SO bad. Apparently, there is no maintenance contract, only "repair on failure."


    I'm trying to get the boss to order the Ecolab grease stripper.

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