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  1. #1

    walk in freezer icing after expansion valve

    When I arrived discharge temp from evap was about 10 degrees.
    everthing after expansion valve frosted over.
    Sight glass was not clear
    outside ambient temp about 20 degrees
    only one condensor fan running due to ambient temp
    cond labeled R404A but there is possibility of mixed refrigerants according to owner
    low psi 3 lb high around 150 and sub cooling to low to read accurately.
    Since I knew siht glass should be flooded wspecially with such low ambient temps I added some 404a.
    low only rose to about 5 lbs high rose to about 250 and sub cooling also went up to about 15 degrees
    Discharge temp in box droped to about 10 degrees and sight glass was still bubbling although not as much.

    At this point something happened between my boss and owner I guess about price so I was asked to pack up and leave but was wondering what you veterens would have done next and if you had to guess what would you think the problem was.

    Also did put into defrost and defrost cyle was working although there did not seem to be any type of pumpdown. Condensor just turned off when t went into defrost.

    Thaks in advance for your response

  2. #2
    Join Date
    Oct 2011
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    Chicagoland Area
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    4,625
    Wht shouldn't a freezer ice up after the valve? Sounds like you have other issues. We need more info before proceeding.
    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
    Understood but I was not there long enough to collect any other data and generally dont spend much time working on freezers. I would expect some frost after expansion valve but is solid ice normal? wouldnt defrost cycle knock that down?

    again was not looking for an answer just some general opinions. More interested in why high side was high but still had bubbles in sight glass. If expansion valves was closeing for any reason plugged, broken overcharged whatever , would that not cause sight glass to clear even faster as liquid backed up to condensor?

  4. #4
    Join Date
    Feb 2006
    Location
    Phoenix,AZ
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    2,889
    Your low side pressure too low for a freezer running 404a. Is your dryer before or after sg?

  5. #5
    Join Date
    Sep 2008
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    Western PA
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  6. #6
    Join Date
    May 2003
    Location
    Utah
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    732
    Quote Originally Posted by indoorairpro View Post
    low psi 3 lb high around 150 and sub cooling to low to read accurately.

    Seriously????

    I would love to hear an explanation on the sub cooling being too low to measure accurately.

  7. #7
    Join Date
    Apr 2010
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    working overtime
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    848
    Step1 if mixture of refrigerants is suspected than before anything else recover, change drier, evacuate and recharge.

  8. #8
    Join Date
    Nov 2011
    Location
    New Hampshire
    Posts
    14
    If I was told there may be mixed gas in system I would have pulled the charge and also changed out FD on system. also after the txv there could be moisture in the system causing the ice up on the lines. next step would have been to do an efficiency test on the comp.

  9. #9
    Join Date
    Aug 2012
    Posts
    39
    Quote Originally Posted by Navy06 View Post
    If I was told there may be mixed gas in system I would have pulled the charge and also changed out FD on system. also after the txv there could be moisture in the system causing the ice up on the lines. next step would have been to do an efficiency test on the comp.
    I'm curious, do you actually repair commercial refrigeration equipment?

    Don't mean to be rude but your recommendations, and a couple of others, really has me wondering...

  10. #10
    Join Date
    Nov 2009
    Location
    Richmond, working under tarps
    Posts
    493
    txv and feeds freezing..........is normal in LT.

    Some of our bigger MT evaps even show frosting at times...dew and freezing point.

    I think when you mentioned subcool is too low to measure, you meant there was NO subcooling, as you indicated the sight glass was flashing.

    As mentioned you need to establish solid liquid to txv, and then measure SH from the evap.

    From there you can make other judgement calls..........but seeing you got called off, its obvious the customer is looking for cheap and dirty fix.

    Look at the TXV label to see what possible refrigerant is in the system.

  11. #11
    Join Date
    Jun 2012
    Location
    Tenn
    Posts
    139
    Quote Originally Posted by malcor View Post
    I'm curious, do you actually repair commercial refrigeration equipment?

    Don't mean to be rude but your recommendations, and a couple of others, really has me wondering...
    With a screen name like NAVY06, I'm guessing he started working refrigeration the same place I started, the Navy and then the Coast Guard. They were funny about that stuff. It didn't take a lot for someone up the chain to decide that since there is a blended refrigerant that the next step (it may be the first step for a compressor has no power at contactor, if the Cheif Engineer was a fine arts major) is to reclaim the charge, weight the bottle and PT it to insure the blend is correct. Over time since retiring from the service, PTing the reclaimed gas is not my first step for troubleshooting, though in most cases I still reclaim critical charges that are low charge and refill by weight whenever the charge is suspected of being low. If NAVY06 stays at it, he will get past those extremely excessive, and unproductive things we all had to do in the service. Let me tell you a story from back when I was active duty. The Coast Guard had a Modspace trailer, and the authorized PM's included a weekly check of the suction pressure. It doesn't matter to the service that every time you put the gage set on it you take two 6 foot hoses of gas out of the system, someone had a bright idea, and I must obey. I requested the short hose and single suction gage, but it never appeared. After about a month and a half of faithfully preforming my duties, as you can guess, the suction pressure was below the very ridged standard set out in the same instruction that required gages on a perfectly fine operating unit. One unit had such a requirement for an ice machine, but after talking to the chief, it was felt that we could skip that. I have no doubt that NAVY06 probably did this awhile with the Navy, and will likely break the bad service methods as time continues.

    There is reason to suspect that there may be a seperated blend, but I don't think it would be my next check. If the blend seperated, I doubt it was from use. Most likely the owner charged as a gas.

  12. #12
    Join Date
    Aug 2012
    Posts
    39
    After noticing hostility towards me I started reading around the other topics here. I have come to realise that people who are learning the trade are encouraged to ‘get their post count up’ with posts that have technical content. Now that I realise that, I can see that my first post in this topic (#9) was uncalled for and out of line. It was a misunderstanding on my part and showed poor judgment.

    It wasn’t my intention to offend anyone and I certainly didn’t want to discourage anyone from participating here, especially someone who is here specifically to increase their knowledge. I made a error in judgement and I apologise for any offence that I may have caused Navy06 and to anyone else that I may have offended too.

  13. #13
    Join Date
    Apr 2010
    Location
    working overtime
    Posts
    848
    It doesn't matter what the system is doing as long as he has a zcontaminated system with mix of refigerants this unit won't work

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