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  1. #1
    Join Date
    Mar 2008
    Location
    South Louisiana
    Posts
    3

    5/16th vs 3/8 discharge line?

    I'm concerned... What will happen if the discharge line is too small?
    I'm checking up on my installer. I've seen a few flags. My equipment was dropped off: 3 ton Am. Standard 16 SEER R-410a, variable air handler, 3/4" suction line and 5/16th's" discharge line (two 50' rolls of each).
    The run will be a little over 70 feet, condenser elevation slightly below air handler with lines going up and back down from attic, only one 90 will have to be used per line.
    Do you think they just grabbed 5/16 instead of 3/8???
    Should I insist on running 3/8???
    I need help before tomorrow.
    Thanks in advance!

  2. #2
    Join Date
    Jan 2008
    Posts
    1,989
    Should be at least 3/8 liquid, and 7/8 suction with that size A/C and length of line set. You better give this guy a closer look. Let him know you're looking for a quality install, not just something slapped in place.

  3. #3
    Join Date
    Sep 2003
    Posts
    1,675
    You could always ask to see the install guide from American Standard

    to see the lineset size in black and white tomorrow.

  4. #4
    Join Date
    Jul 2002
    Location
    Zelienople, Pa
    Posts
    2,965
    You'll need a 3/4 X 3/8 lineset for that.
    How tall are you Private???!!!!

  5. #5
    Join Date
    Jun 2005
    Location
    Near Chicago, IL
    Posts
    3,317
    3/4 x 3/8

  6. #6
    Join Date
    Mar 2008
    Location
    South Louisiana
    Posts
    3
    wow! Thanks for the quick response.

    Any other things to look for such as the way the lines are "preped" ex. vac drawn, nitrogen used or not...
    I've been trying get as much info as possible after getting the run-around etc...

  7. #7
    Join Date
    Jun 2007
    Location
    Round Rock
    Posts
    3,540
    I would see what Trane recommends. 3/8" on the high side definitely and maybe even 7/8" on the low side. That is a pretty long run. Otherwise, you better buy the 10 year parts and labor, cause you're gonna be popping compressors with the 5/16" high side. I would make sure it isn't 5/16" sized for plumbing, because that is 3/8" on refer. Plumbers sizes are different than ours.

  8. #8
    Join Date
    Feb 2008
    Location
    ga.
    Posts
    85
    Needs a real good vacuum pulled. Find out if they use micron gages. If no then you will not know if a good vacuum pulled. If yes Being its a new line set and coil, should pull at least 500 micron vacuum. The lower the better.
    Definition of insanity is to do the same thing over and over expecting a different result.

  9. #9
    Join Date
    Mar 2008
    Location
    South Louisiana
    Posts
    3
    Just cause I left out the details earlier it is a Heritage 16 Heat Pump with "a two-step Duration compressor with two-stage cooling which runs at 70% capacity most of the time, and steps up to the second stage on the hottest days" blah-blah...

    It's definatly ref line... I think someone just grabbed the wrong size. I was just making sure it wasn't something I was missing like trying to increase velocity of the liquid back to the air handler or something due to the long run.
    It didn't seem right, that's why I had to ask, thanks.

  10. #10
    Join Date
    Jul 2005
    Posts
    5,489
    Quote Originally Posted by CBRrr View Post
    Just cause I left out the details earlier it is a Heritage 16 Heat Pump with "a two-step Duration compressor with two-stage cooling which runs at 70% capacity most of the time, and steps up to the second stage on the hottest days" blah-blah...

    It's definatly ref line... I think someone just grabbed the wrong size. I was just making sure it wasn't something I was missing like trying to increase velocity of the liquid back to the air handler or something due to the long run.
    It didn't seem right, that's why I had to ask, thanks.
    That was very nice of you to think about giving them the benefit of the doubt

    Especially with high efficiency systems, it needs to be installed correctly. Undersized refrigerant lines will reduce capacity and efficiency.

  11. #11
    Join Date
    Aug 2007
    Location
    Northern VA 38 degrees N by 76 degrees W
    Posts
    5,060

    Exclamation

    Quote Originally Posted by CBRrr View Post
    I'm concerned... What will happen if the discharge line is too small?
    I'm checking up on my installer. I've seen a few flags. My equipment was dropped off: 3 ton Am. Standard 16 SEER R-410a, variable air handler, 3/4" suction line and 5/16th's" discharge line (two 50' rolls of each).
    The run will be a little over 70 feet, condenser elevation slightly below air handler with lines going up and back down from attic, only one 90 will have to be used per line.
    Do you think they just grabbed 5/16 instead of 3/8???
    Should I insist on running 3/8???
    I need help before tomorrow.
    Thanks in advance!
    3/8th and 3/4

    Maximum linear length 80 feet

    Maximum vertical lift 25 feet

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