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  1. #1
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    Oct 2018
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    >50ft Suction line question

    Im an HVACR student and almost done with my training so I’m trying to understand something about my system as a contractor hit the suction line when sawing through my floor. The system is a Goodman 2 ton 18seer two stage condenser I’ll add model number in a little bit. The coil is a 3-ton coil. Refridgerent is r-410a. Riser hight is 12ft then a horizontal of 55ft and the system has 3 90’s on a pipe that for some reason is dissimilar diameter. The installed pipe is 3/4 up the riser and down 40ft of the horizontal then it changes to 1/2 before going into the evaporator coil. Why might have this been done? I know the line needs 1000fpm of circulation so I thought ok maybe they reduced it to keep the speed at the cost of capacity but it didn’t make since to me to do that 2/3 the way down the horizontal where there is a sag

    Coil:CHPF3636B6 GMVC960403BN GSXC180241 TX2N4 : Goodman CHPF - 3 Ton - Horizontal A Coil


    Condenser: CHPF3636B6 GMVC960403BN GSXC180241 TX2N4 : Goodman GSXC18 - 2 Ton - Air Conditioner - 18 Nominal SEER - Two-Stage - R-410

    CHPF3636B6 GMVC960403BN GSXC180241 TX2N4 : Goodman GMVC96 - 40k BTU - Two-Stage Gas Furnace - 96% AFUE

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  3. #2
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    Aug 2002
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    Look up:

    Dupont’s best piping practices

  4. #3
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    Also that’s 1/2” ACR?

  5. #4
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    Thread Starter
    Quote Originally Posted by pecmsg View Post
    Also that’s 1/2” ACR?
    Yes


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  6. #5
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    Nov 2004
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    WHY?
    … have to ask the installer.

    Penalty for refrigerant pipe routing: ~ 500 BTU/HR Loss [maybe ~2% ?]
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  7. #6
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    Quote Originally Posted by dan sw fl View Post
    WHY?
    … have to ask the installer.

    Penalty for refrigerant pipe routing: ~ 500 BTU/HR Loss [maybe ~2% ?]
    Am I correct in thinking that it would be best just to have a 3/4 line all the way in gaining some capacity? I know given it’s 2-stage system we are sizing for approx 66% or ~1.3 ish tons and the line length is less than 80’ so it’s not “long” the condenser is below the evaporator so there isn’t any issues to overcome gravity on the suction side.


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  8. #7
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    Post pics of the piping. No reason to decrease the pipe size like you describe it.
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  9. #8
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    Apr 2003
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    St. Louis
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    1/2" on the suction line before going to 3/4"?
    2 ton condenser on a 3 ton coil doesn't make sence to me. I would have to call goodman tech and ask them. Also would have to know what type of expansion device is used and what size or number is it

  10. #9
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    Dec 2012
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    You mean the suction line? In anycase its not properly installed. For 50ft/3 ton should be more like 1-1/8” ll would be fine for 3/8 across any length.

    Rundawg could probably post the actual install manual for this unit


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  11. #10
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    Quote Originally Posted by Alwayslearning2 View Post
    Am I correct in thinking that it would be best just to have a 3/4 line all the way in gaining some capacity?
    This set up is an AHRI matched set (# 10332332).

    The Installation Manual and “Long Line Guidelines” (even though this isn’t considered long- greater than 79 feet) shows the optimum suction line size for your 2 ton outdoor unit @ 72 feet equivalent length, is a 3/4” suction line.

    With 3/4”, there is only a 1% capacity loss up to 200 feet in equivalent length.

    If the entire suction line was installed with 5/8”, the capacity loss at your 72 feet, is only 2%.

    Note: 7/8” and above suction lines are not approved for 2 ton, 2 stage systems.

    Why they reduced the suction line 2/3's the way through the horizontal run is any ones guess. My guess is - they ran out of 3/4” and installed what ever they had left in the truck.

    Correcting the suction line size to all 3/4" would bring it back to what the manufacture spec’d, but I’m thinking if the unit is sized properly for the space, you will not notice the small capacity loss leaving it as is.
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  13. #11
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    Thread Starter
    Quote Originally Posted by rundawg View Post
    This set up is an AHRI matched set (# 10332332).

    The Installation Manual and “Long Line Guidelines” (even though this isn’t considered long- greater than 79 feet) shows the optimum suction line size for your 2 ton outdoor unit @ 72 feet equivalent length, is a 3/4” suction line.

    With 3/4”, there is only a 1% capacity loss up to 200 feet in equivalent length.

    If the entire suction line was installed with 5/8”, the capacity loss at your 72 feet, is only 2%.

    Note: 7/8” and above suction lines are not approved for 2 ton, 2 stage systems.

    Why they reduced the suction line 2/3's the way through the horizontal run is any ones guess. My guess is - they ran out of 3/4” and installed what ever they had left in the truck.

    Correcting the suction line size to all 3/4" would bring it back to what the manufacture spec’d, but I’m thinking if the unit is sized properly for the space, you will not notice the small capacity loss leaving it as is.
    Ok thanks! The line got sliced as I said before so I figured if they are going to braze it maybe just replace the weird diameter shift with 3/4 all the way to coil and call it a day they cut the line hotdog style not traverse. I was just scratching my head going what HVAC sorcery is this


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  14. #12
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    Apr 2003
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    A thing to remember is all condensing units have a maximum line length and size. Not because of capacity loss but compressor capacity of oil. These compressors are getting smaller physical in size and with added oil for length of line at some time all the can come back to the compressor to much oil - whats the old saying a compressor turns to junk when it pumps liquid.

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