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  1. #1
    Join Date
    Aug 2008
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    Landenberg, PA
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    Thoughts on insulating refrigerant lines

    I am wondering....

    On an A/C indoor coil and outside condenser, the low (big) refrigerant line is insulated and the small one is not. Why?

    Assuming we are trying to cool a house, wouldn't a high line (small) that is exposed inside the house radiate heat into the house? Wouldn't insulating it where it runs inside the house make the system a bit more efficient?

    On my a/c, the low line is insulated all the way out to the condenser. But it is exposed for about 12" inside the condenser where it sweats like crazy. Wouldn't insulating this section help with efficiency by allowing it to absorb less of the outside heat before entering the house?

    Steve

  2. #2
    Join Date
    Jun 2005
    Location
    SW Wisconsin
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    5,025
    The big line is superheated vapor coming back to the compressor.
    The evaporator absorbs heat from the air.

    The few times the small liquid line needs insulating is if it is in an extremely hot area, such as on a tar roof.

  3. #3
    Join Date
    Aug 2008
    Location
    Landenberg, PA
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    72
    Quote Originally Posted by udarrell View Post
    The big line is superheated vapor coming back to the compressor.
    It's carrying the heat removed from the house to the compressor right? So isn't the last 12" of it that is uninsulated just absorbing more heat from outside that now the compressor/condenser unit has to work to remove?

    Steve

  4. #4
    Join Date
    Nov 2004
    Location
    NJ
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    1,204
    Yes you are right.

    Go to the store and buy what you need to insulate the pipe.

    Or better yet pay a contractor to do it.

    I doubt you'll save over the life of the unit what it costs in time and materials to perform this task, but you sound determined that it is the right thing to do, so I'll tell you it is, be like a sneaker
    Ed J

  5. #5
    Join Date
    Aug 2008
    Location
    Landenberg, PA
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    Quote Originally Posted by Ed Janowiak View Post
    Yes you are right.

    Go to the store and buy what you need to insulate the pipe.

    Or better yet pay a contractor to do it.

    I doubt you'll save over the life of the unit what it costs in time and materials to perform this task, but you sound determined that it is the right thing to do, so I'll tell you it is, be like a sneaker
    That's kinda what I was wondering-if it would save much. Sounds like it won't. Thanks much for the information.

  6. #6
    Join Date
    Jan 2004
    Location
    Lancaster PA
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    68,599
    12" of uninsulated vapor line. Will absorb about 30 BTUs an hour.

    The heat the liquid line is radiating into the house. Is also less heat in the liquid, for when it goes into the evap coil to absorb heat from the house. So for all heat that you prevent from radiating from the line. You also absorb less from the house.

    If the liquid line runs into the attic. Then it can be worth insulating it.
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  7. #7
    Join Date
    Aug 2008
    Location
    Landenberg, PA
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    Quote Originally Posted by beenthere View Post
    12" of uninsulated vapor line. Will absorb about 30 BTUs an hour.

    The heat the liquid line is radiating into the house. Is also less heat in the liquid, for when it goes into the evap coil to absorb heat from the house. So for all heat that you prevent from radiating from the line. You also absorb less from the house.

    If the liquid line runs into the attic. Then it can be worth insulating it.
    Okay, thanks. The BTU rating on my A/C, is that also per hour or is it per some other unit of time? My unit is 60,000 BTUs.

  8. #8
    Join Date
    Jan 2004
    Location
    Lancaster PA
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    68,599
    Its per hour.
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  9. #9
    Join Date
    Aug 2004
    Location
    North Richland Hills, Texas
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    14,915
    If 12" of uninsulated suction line absorbes 30 btu per hour, then insulating it could result in a net capacity gain of 0.0005% for a 5 ton system.

    If the system cost $1 per hour to run, and it ran for an average of 10 hours a day during the cooling season, insulating that 12" of suction line could save you 15 cents a month during the cooling season.
    If the cooling season was 6 months long, it could save you 90 cents a year.
    Hardly worth being concerned about...
    If more government is the answer, then it's a really stupid question.

  10. #10
    Join Date
    Jun 2007
    Location
    Round Rock
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    3,623
    The liquid line doesn't sweat either. Insulation the suction line keeps water from getting in your attic insulation and in your wall. Water and sheetrock usually don't mix very well.
    I like DIY'ers. They pay better to fix.

  11. #11
    Join Date
    Aug 2008
    Location
    Landenberg, PA
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    72
    Quote Originally Posted by mark beiser View Post
    If 12" of uninsulated suction line absorbes 30 btu per hour, then insulating it could result in a net capacity gain of 0.0005% for a 5 ton system.

    If the system cost $1 per hour to run, and it ran for an average of 10 hours a day during the cooling season, insulating that 12" of suction line could save you 15 cents a month during the cooling season.
    If the cooling season was 6 months long, it could save you 90 cents a year.
    Hardly worth being concerned about...
    I like responses like this.

  12. #12
    Join Date
    Jun 2010
    Posts
    23
    So I was searching for a thread like this, I have some similar questions. I had an HVAC guy come out to check some leaking in the a-coil box. I guess the whole unit was slanting in one direction, and I think the drain pipe was not working well. It was covered by the home warranty.

    But what I believe may not be covered is the rat problem previous owners had. They seemed to have chewed half of the cold pipe's insulation for a good 10' or more. I haven't checked other locations yet that may be low enough for the rodents. But those pipes are sweating like crazy. The roof is sort of vaulted high, and just the first lower few feet when I popped into the attic I measured with a small thermal surface meter (PE-1 TempGun) and read 120 deg F. It was probably only low 90s outside. The peak of the attic must have been more.

    But anyway, all of the cold line is insulated, except for the rodent bites, and the smaller hot line is not insulated at all. From the furnace in the garage, to the attic, to the outside compressor, no insulation on the smaller hot line. Would there be any benefit to putting insulation on the hot line when the local temperature can be 80-100 deg in the summer (only about 2' exposed outside) and the attic and garage can be 120-130 deg?

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