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Thread: air in system?

  1. #1
    Join Date
    Jul 2004
    Location
    NJ
    Posts
    1,795
    I am gonna try not to be long and boring this time.
    I went on a job today,thats a 44 feet long open meet cooler in a supermarket.case temp.was around 50*F.found sight glass not full.some plastic bags on the condensor.removed the bags.found a can of R22 in the condenser unit.ussumed refrigereant was R22.310 psi head,63psi back.ambient temp.100*F.very hot discharge pipe(burnt my arm).filled the sight glass.head settled at 325psi,back settled at 65-63psi. RLA info was 42.6 amp.settled at 37-38 amp.condensor looks clean.case temp doesn`t change.also compressor is low in oil.monday I am gonna clean the cond.,put oil in comp.,pull vacuum and recharge the system.do you guys think there is air in the system?

  2. #2
    What was the temp of the case discharge air, when you were ready to leave?

    Was product in the case when you arrived?

    Did the store manager agree to leave case as is until next week?


  3. #3
    Did you verify all of your evaporator fans were in correct operation?

    Did you verify your subcooling was ten degrees at condensor outlet?

    Were each of the coils inside the cases feeding corectly? Evenly? Same temp across each and every coil?

    Was there any air flow blockage in your honeycomb?
    What was your CFM?

    I assume you have a velometer. I just got one on ebay for $65, NEW, Fieldpiece.
    So money is not an excuse for not using one.

    Is there a small filter drier located inside the cases which acts as a pre-filter for the expansion valves?
    If so, (and there possibly is), you need to check for a temperature drop across the drier. I had one a couple weeks ago that was 20degrees temp drop. AUGH!!!


    Make sure none of them fans are freewheeling backwards.
    Those fans live to give you trouble and fool you.


    Without the load being down to temp, superheat is not a real temp to be reconed with right now.
    Although subcooling is something that can help you diagnose your system.


    If you go adding refrigerant and there is noncondensibles in the system, your head pressure is gonna climb outa sight! And your NOT gona see any subcooling because your condensor is all used up.


    The only thing we havent touched on yet is your headmaster. But I'm sure you have figured if that is giving you any trouble.



    Oh ... and what you wrote abouit the condensor looking clean ... uh ....don't do that! Don't do that! DON'T DO THAT!


    Check with your office and have them look up the last time your company had a guy out there to hose down those RTU condensors.
    If it's been awhile, drag out the hose and do it yourself!

    With symptoms of high head and the case is not cooling ... always assume your condensor IS dirty!

    And dont rule out you could also have a weak compressor.
    Remember what time of the year it is .... The Dog Days of August are creeping closer every hour!
    And pretty soon nothing will be running right!


    Since your one of the elite who services super market refrigeration systems ... I know well and good that you took down your model number off that compressor.
    If you got the time, go visit the manufacturer's website this week end and download the compressor curve for that particular unit.

    This way, when you return to that store on Monday, you will be fully equiped to challenge that system and figure out just what is wrong with it, totally!
    That curve will tell you what the amps should be at all the pressure ranges.








    [Edited by R12rules on 07-17-2004 at 07:26 PM]

  4. #4
    Join Date
    Jan 2004
    Location
    Fort Worth, TX
    Posts
    204
    Sounds like you should of cleaned the coils first before heading home...............................that was probally your solution.

  5. #5
    Join Date
    Jul 2004
    Location
    NJ
    Posts
    1,795
    Originally posted by R12rules
    Did you verify all of your evaporator fans were in correct operation?

    Did you verify your subcooling was ten degrees at condensor outlet?

    Were each of the coils inside the cases feeding corectly? Evenly? Same temp across each and every coil?

    Was there any air flow blockage in your honeycomb?
    What was your CFM?

    I assume you have a velometer. I just got one on ebay for $65, NEW, Fieldpiece.
    So money is not an excuse for not using one.

    Is there a small filter drier located inside the cases which acts as a pre-filter for the expansion valves?
    If so, (and there possibly is), you need to check for a temperature drop across the drier. I had one a couple weeks ago that was 20degrees temp drop. AUGH!!!


    Make sure none of them fans are freewheeling backwards.
    Those fans live to give you trouble and fool you.


    Without the load being down to temp, superheat is not a real temp to be reconed with right now.
    Although subcooling is something that can help you diagnose your system.


    If you go adding refrigerant and there is noncondensibles in the system, your head pressure is gonna climb outa sight! And your NOT gona see any subcooling because your condensor is all used up.


    The only thing we havent touched on yet is your headmaster. But I'm sure you have figured if that is giving you any trouble.



    Oh ... and what you wrote abouit the condensor looking clean ... uh ....don't do that! Don't do that! DON'T DO THAT!


    Check with your office and have them look up the last time your company had a guy out there to hose down those RTU condensors.
    If it's been awhile, drag out the hose and do it yourself!

    With symptoms of high head and the case is not cooling ... always assume your condensor IS dirty!

    And dont rule out you could also have a weak compressor.
    Remember what time of the year it is .... The Dog Days of August are creeping closer every hour!
    And pretty soon nothing will be running right!


    Since your one of the elite who services super market refrigeration systems ... I know well and good that you took down your model number off that compressor.
    If you got the time, go visit the manufacturer's website this week end and download the compressor curve for that particular unit.

    This way, when you return to that store on Monday, you will be fully equiped to challenge that system and figure out just what is wrong with it, totally!
    That curve will tell you what the amps should be at all the pressure ranges.








    [Edited by R12rules on 07-17-2004 at 07:26 PM]

    unfortunately I am not one of the elite to service supermarket ref.systems but hey there`s no body else my boss can send to a job like that.I think I have a good chance to become one.and I appreciate your response.
    most of the things you told about I didn`t do,I was also in touch with my boss who has been doing this for nearly 30 years.but I suspected the compressor and tried to test it which I forgot to ask about in my post.frontseated the suction service valve it pulled down to 15 inches.when I stopped jumping the LPC, in 40 sec.it came back to 0 psi,and in 3 min.it was up to 50 psi. I thought I found the culprit but my boss didn`t think so.
    if the filter before the exp.valve was clogged shouldn`t I see a low back pressure?
    I don`t have a velometer I also don`t know how to use it on honeycomb.I verified an air flow by hand though.also if it was an airflow problem I would have a low back pres.wouldn`t I.what really intrigues me is how do I get a low running amp with high back pressure.and more of charge didn`t change the amp draw..
    temp around the cond.went between 100 and 108*F.I don`t think there is a dramatic high pressure for that temp.if I have to add 30*F to amb.temp.but what do I know ,maybe when I flash it monday you and my boss will turn right and it won`t bother me either.
    I should also say that I didn`t take the product out to check how many expansion valves there were but in four sections the four thermometers showed the same temps.I spent there enough time to not suspect or ask about the meat being hot.also the owner would know better not to panic about it.by the way when I told him that we have to come back on monday he sad "how come you couldn`t fix it everybody else does ,they put some freon and "whatever..what if they put some air too.`cause when I dropped the high side to 300 psi in the start the sight glass got half..

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