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  1. #1
    Join Date
    May 2016
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    3
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    New Install, struggling to cool.

    My first post, hope I get it right:
    My company installed a unit in Febuary of this year and Saturday we got a call for no or limited cooling. I was sent out and this is what I found:
    1. The outside air that day was 90F
    2. The thermostat in the house was reading 79F ( I double checked temperature accuracy of the thermostat with my meter.)
    3. Supply air at plenum was 62F
    4. Air entering return was 78F.
    5. Suction pressure: 135, Discharge : 305 (410A) Suction Line temp: 85 Liquid Line Temp: 95
    6. SC was 3-6 while I was there, but adding and recovering refridgerant had no effect on my discharge pressure.
    7. Amp draw L1: 12.6, L2:12.4 at the condenser. Compressor rated RLA is 18.5

    There was a family gathering at the residence that day, so there was a definite added heat load. My main concern though is with the lower discharge pressure and warm suction line.

    Thanks in advance!

  2. #2
    Join Date
    Jan 2012
    Location
    Arrowhead Stadium
    Posts
    833
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    Heat pump? Txv? Model and serial numbers.

  3. Likes Metalman0880 liked this post
  4. #3
    Join Date
    May 2016
    Posts
    3
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    Heat pump and TXV. GSZ140481KB Condenser, AVPTC48D14AC Air Handler

  5. Likes Metalman0880 liked this post
  6. #4
    Join Date
    Jan 2008
    Posts
    15
    Post Likes
    Quote Originally Posted by krusader76 View Post
    My first post, hope I get it right:
    My company installed a unit in Febuary of this year and Saturday we got a call for no or limited cooling. I was sent out and this is what I found:
    1. The outside air that day was 90F
    2. The thermostat in the house was reading 79F ( I double checked temperature accuracy of the thermostat with my meter.)
    3. Supply air at plenum was 62F
    4. Air entering return was 78F.
    5. Suction pressure: 135, Discharge : 305 (410A) Suction Line temp: 85 Liquid Line Temp: 95
    6. SC was 3-6 while I was there, but adding and recovering refridgerant had no effect on my discharge pressure.
    7. Amp draw L1: 12.6, L2:12.4 at the condenser. Compressor rated RLA is 18.5

    There was a family gathering at the residence that day, so there was a definite added heat load. My main concern though is with the lower discharge pressure and warm suction line.

    Thanks in advance!
    What's the original load on the house calculated at? What was it designed at? A lot of questions that go into this. An additional 15 people in the house would yield 6,450 btu's to the load, and that's if they're sitting still. If they're active or moving around (kids playing, etc...), you could go from 400+ btu's per person to 800+. The warm suction line is a concern, but people load and constant opening/closing of doors could take you to 5.0+ tons in an instant if it's an "active" gathering.

  7. #5
    Join Date
    Jan 2012
    Location
    Arrowhead Stadium
    Posts
    833
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    Not sure but I believe the install manual has direction for adjusting sh to between 5-7 and sc to 7.

  8. Likes Bazooka Joey liked this post
  9. #6
    Join Date
    Feb 2014
    Location
    Statesville NorthCarolina
    Posts
    158
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    I would go back and look in the attic space and see how much insulation is in there, I've seen units that were right on the money, that wouldn't keep up when it was in the heat of the day but would cool down at night just fine, people had to add more insulation in attic, problem solved, also check to make sure the strip heat is not stuck on

  10. #7
    Join Date
    Mar 2015
    Location
    Tx
    Posts
    657
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    6 degrees of sub cooling unit is undercharged . Get that fixed then look at other potential causes

  11. Likes icy78 liked this post
  12. #8
    Join Date
    Mar 2015
    Location
    Medford, N.Y.
    Posts
    2,306
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    Lets see,r-410a,90*ambient,that should give a 400+psi head press and you had 305psi.

  13. #9
    Join Date
    Dec 2003
    Location
    Citrus County, Florida
    Posts
    2,279
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    undercharged
    Doug

  14. #10
    Join Date
    Mar 2015
    Location
    Medford, N.Y.
    Posts
    2,306
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    Just a Q. How many degree of SC is needed for a res AC system. Cond unit on the ground,evap 22'up in the attic and 20' across the attic?

  15. #11
    Join Date
    Sep 2014
    Location
    Portland, Oregon, United States
    Posts
    107
    Post Likes
    Possibly airflow issue. I'd verify the airflow is not an issue if nothing changes when you adjust charge. Dust work in attic? Is there an attic fan?

  16. #12
    Join Date
    Mar 2015
    Location
    Tx
    Posts
    657
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    Quote Originally Posted by TechmanTerry View Post
    Just a Q. How many degree of SC is needed for a res AC system. Cond unit on the ground,evap 22'up in the attic and 20' across the attic?
    9 to 15 degrees of SC depending on tonnage,seer etc. . Mfg should label required sc but not all do. If no guide then its just a WAG but you still havetoget a 45 to 50 degree evap temp ( just a guide that your close) & 15 + rise on condenser ,again just a your close numbers.The old 7,8,9 seer r22 needed 30d rise on condenser but not a lot of them left.
    With Lineset that long and undercharged its probably "flash gassing" before getting to coil in attic

  17. #13
    Join Date
    Mar 2015
    Location
    Medford, N.Y.
    Posts
    2,306
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    Can I get a more specific amount of SH, like, say, 8*SH is needed (if it is)on this 14SEER or 10*SH for that 13SEER system? Thats w/ the LL length as mentioned.All that is required is a full LL at the TXV, right?

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