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  1. #1
    Join Date
    Jan 2012
    Location
    Oregon
    Posts
    101

    Iced up suction line

    Is it normal to have a iced up suction line? The unit is a r408 freezer that is running TXV valves. I just want to make sure it won't hurt the compressor. I'm a newbie and this is the first time I've encountered this. Thanks Rusty

  2. #2
    Join Date
    Oct 2012
    Posts
    3,292
    Yes you will get ice on the suction line for a freezer, its cold.

    As far as the compressor, check the superheat on the suction line at the compressor. Should be at least 20* superheat at the compressor to protect it from liquid floodback.

  3. #3
    Join Date
    Jan 2012
    Location
    Oregon
    Posts
    101
    Thanks for the help. Should I worry if the suction line ices up all the way back to the compressor?

  4. #4
    Join Date
    Oct 2012
    Posts
    3,292
    Quote Originally Posted by bigbucks View Post
    Thanks for the help. Should I worry if the suction line ices up all the way back to the compressor?
    The only good way to know for sure is checking the superheat at the compressor. It is normal to see frost pretty close to the compressor, but not a good rule of thumb to go by. All depends on the system, length of lines, etc...

    Think of it this way though, your evaporator temp is well below 0. Even by the time the gas gets back to the compressor it is still below 32* and will create frost.

    If your superheat at the compressor is less than 20*, you want to check at the evaporator(s) for proper superheat and make sure something isn't flooding back.

  5. #5
    Join Date
    Jan 2010
    Posts
    6,058
    No, they can be covered with frost.

  6. #6
    Join Date
    Jan 2012
    Location
    Oregon
    Posts
    101
    Ok thanks for the info.

  7. #7
    Join Date
    Mar 2013
    Location
    swan valley idaho
    Posts
    719
    If no frost then line is above 32. If sst is -20 then you would be over 50 super heat. Not good

    So ya almost any walk in freezer should have a frosty line all the way back

  8. #8
    Join Date
    May 2003
    Location
    Utah
    Posts
    718
    Quote Originally Posted by VTP99 View Post
    No, they can be covered with frost.
    Completely true.

    Low temp application running a saturated suction of -20*F with 40* superheat at the compressor inlet. Do the math.....that's a 20*F temperature at the compressor inlet.

    The suction piping, suction service valve and perhaps part of the compressor endbell will have frost on it. So what???? It's a simple indication of a temperature below freezing...nothing more.

    Without checking the superheat you have no idea whether this condition is dangerous (liquid present).

  9. #9
    Join Date
    May 2005
    Posts
    1,347
    i had a copeland tech tell me the compressor can be covered in ice..and still be Ok..

    that said, i will set the superheat at the compressor..to protect the compressor..
    Let's give nukes a chance.

  10. #10
    Join Date
    Mar 2013
    Posts
    44
    Set the superheat at the compressor. there is one id like to see. considering the TEV is at least 1 wall apart from you. =p

    I am a bit baffled as to why an accumulator isn't on it (assuming it has a pretty short run, if you're getting good frost all the way back)
    Also be sure it's insulated with 3/4' or 1''.. otherwise ya, 20-30 SH is on the money. don't let it fall below that.

  11. #11
    Join Date
    May 2005
    Posts
    1,347
    i always set compressor superheat, i could care less what the superheat is at the evap, i want that compressor to be protected..
    Let's give nukes a chance.

  12. #12
    Join Date
    Jan 2010
    Posts
    6,058
    Quote Originally Posted by primmers View Post
    i always set compressor superheat, i could care less what the superheat is at the evap, i want that compressor to be protected..
    That could start some debate if your including refrigeration.

  13. #13
    Join Date
    May 2005
    Posts
    1,347
    if the superheat at the compressor is Ok the case/box is gona be ok.....right?
    Let's give nukes a chance.

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