Carrier RTU second stage freezing up - Page 3
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  1. #27
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    Quote Originally Posted by Dallas Duster View Post
    Subcooling is high because it's a fixed orifice. With a 25 degrees delta T I would say airflow too.
    True. Thank u sir.

  2. #28
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    I had very similar problem, a fire damper was the culprit. good luck and keep us posted.

  3. #29
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    What were your readings on first stage? Both circuits should have the same airflow, correct?

  4. #30
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    Feb 2005
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    Quote Originally Posted by qwerty hvac View Post
    Here are some numbers:

    SH 8.5
    SC 28.6
    High side 199.6
    Low Side 48.3
    Ambient temp 72.7
    Condenser discharge 92.7
    Supply temp 41.5
    Return temp 67.1
    compressor discharge temp 71.8
    suction temp 33.1
    There's a couple things that don't make sense. A restriction in the drier or feeder tubes would not be able to freeze the entire coil or give you an 8.5 degree SH. Not to mention a 26 degree split. Also your compressor (or condenser) discharge temperature in no way can be lower than your ambient temperature. May want to double check your equipment.
    ## + years in the field never made you a know-it-all This industry is far more diverse than you are

  5. #31
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    Quote Originally Posted by git-r-dun View Post
    There's a couple things that don't make sense. A restriction in the drier or feeder tubes would not be able to freeze the entire coil or give you an 8.5 degree SH. Not to mention a 26 degree split. Also your compressor (or condenser) discharge temperature in no way can be lower than your ambient temperature. May want to double check your equipment.
    Discharge temp can't be lower than SCT either. That's why I made the statement about insulating the temp sensors to the line. There's a lot of air moving past the temp sensors on that package unit. The SC is probably lower than reported too, for the same reason.

  6. #32
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    Speaking from experience Ive had partially restricted driers cause coils to freeze up and those Carriers before and on Tranes with the same manifold design.

    Not restricted enough to notice a delta but enough to cause what hes describing.

    A bad manifold is usually just one or two metering devices thst cant be cleared.

    Ivr tried R11 flush before and no luck.

  7. #33
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    Quote Originally Posted by commtech77 View Post
    Speaking from experience Ive had partially restricted driers cause coils to freeze up and those Carriers before and on Tranes with the same manifold design.

    Not restricted enough to notice a delta but enough to cause what hes describing.

    A bad manifold is usually just one or two metering devices thst cant be cleared.

    Ivr tried R11 flush before and no luck.
    I will find out more tomorrow when I go there. I bet it's a drier or airflow issue. I hate calls like this because I have been thinking about it all weekend.


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  8. #34
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    I read something here about drilling a small hole on the header right behind the plugged up orifices and removing the crap with a piece of thin wire. seems like a good idea, haven't had the chance to try it.

  9. #35
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    Jul 2007
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    Delta BC Canada
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    Hmm

    Try running 2nd stage as first stage and see what your readings are . It may point you towards an an airflow issue.

  10. #36
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    Feb 2005
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    Quote Originally Posted by commtech77 View Post
    Speaking from experience Ive had partially restricted driers cause coils to freeze up and those Carriers before and on Tranes with the same manifold design.

    Not restricted enough to notice a delta but enough to cause what hes describing.

    A bad manifold is usually just one or two metering devices thst cant be cleared.

    Ivr tried R11 flush before and no luck.
    Checking for restricted feeder tubes is easy. Remove belt/ disable fan and see which ones are not frosting. I still don't see how a restricted drier gave you an 8 degree superheat and a 20+ delta (supply/ return air). Restriction or plugged distributor= loss capacity=higher SH=lower delta. Seems like there's enough air for unit at half capacity and not full. At least that's the angle I'd take based on that info.
    ## + years in the field never made you a know-it-all This industry is far more diverse than you are

  11. #37
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    Quote Originally Posted by git-r-dun View Post
    Checking for restricted feeder tubes is easy. Remove belt/ disable fan and see which ones are not frosting. I still don't see how a restricted drier gave you an 8 degree superheat and a 20+ delta (supply/ return air). Restriction or plugged distributor= loss capacity=higher SH=lower delta. Seems like there's enough air for unit at half capacity and not full. At least that's the angle I'd take based on that info.


    those were his readings not mine. Half a coil is freezing up on me on a unit thats never had service issue one the drier is coming out.
    if its not thr manifold on those carriers its the drier. Thats always been my experience.

    the filters are usually inside the unit. you talk to the tennants and ask them if their 2 or 3 or 5 year old unit has ever dropped water down the return , they say no then you pull the drier.

  12. #38
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    pull vacuum and weigh the charge back in and it fixes ir. Get off the roof and hit the next roof because its Houston, its July and your boss is pushing you.

    Also you pull the belt on one of those units the manifold is going to freeze bad or not.

  13. #39
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    Dec 2008
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    Well I found that it is a duct restriction. Name:  ImageUploadedByTapatalk1337027227.599657.jpg
Views: 100
Size:  14.1 KBName:  ImageUploadedByTapatalk1337027246.366945.jpg
Views: 117
Size:  19.9 KB
    Don't know if you can see it in the pic but when the blower starts up the return sucks in pretty good. I open up the filter cover and let it run on outside air and the freeze stops. I was told to do no more because this system is only a year old. It looks like a nice install but the return is only 20" round going to that plenum. Let the engineer figure it out. Lol


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