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  1. #1
    Join Date
    Nov 2012
    Posts
    31

    Return Plenum and transition

    Hi
    I'm changing pretty much my whole system today. But the ceiling boxes. The are replacing duct work, supply plenum, AC furnace and coil.
    They are NOT replacing the return plenum and transition. They are saying it looks fine. I see that the insulation looks black from dust but they insist is fine.
    Should these pieces be changed or this won't affect anything?

  2. #2
    Join Date
    May 2004
    Location
    south louisiana
    Posts
    3,231
    I'd change it.
    some ductboard has black coatings
    sheetmetal insulation has black facing into plenum.
    return leakage contributes to high RH in our climate.

    this leakage is past the filter, so where this sucks in
    air it brings air/dust etc to collect on coil.

    dust is an indication of leakage. at the minimum
    clean off dust and make sure that they mastic seal all
    the connections.

    same with supply plenum connections and each supply duct take off.
    sealing supply boxes at ceiling will help reduce duct loss also.

    best of luck.
    The cure of the part should not be attempted without the cure of the whole. ~Plato

  3. #3
    Join Date
    Nov 2012
    Location
    Tahlequah OK
    Posts
    131
    How old is your system and how long of a run is your RA duct? Is it round or square duct? The duct insulation used years ago had a tar impregnated paper facing that turned dark over time. I agree with energy_rater that you should at least have them check the duct for air leaks. Take a look at the air entering side of the evaporator coil. If it is real dirty than you know you are bypassing the air filter somewhere which is most likely your RA duct.

  4. #4
    Join Date
    Nov 2012
    Posts
    31
    Quote Originally Posted by energy_rater_La View Post
    I'd change it.
    some ductboard has black coatings
    sheetmetal insulation has black facing into plenum.
    return leakage contributes to high RH in our climate.

    this leakage is past the filter, so where this sucks in
    air it brings air/dust etc to collect on coil.

    dust is an indication of leakage. at the minimum
    clean off dust and make sure that they mastic seal all
    the connections.

    same with supply plenum connections and each supply duct take off.
    sealing supply boxes at ceiling will help reduce duct loss also.

    best of luck.
    They are changing the supply plenum. they are going to clean dust and they also are saying that the whole home purifier is after the return so that stuff is not going to make it to the system. They say it doesn't look bad.

    I don't know much about this stuff so I don't know what is bad or what is not.

  5. #5
    Join Date
    May 2004
    Location
    south louisiana
    Posts
    3,231
    if it is dirty..you have leakage. return leakage contributes
    to high RH indoors.
    if they don't want to do the work..they will
    say it is ok.

    are they using mastics to seal new supply plenum?
    don't let them duct tape of foil tape the leakage
    it might seal now..but later it will leak.

    we've seen other systems to base
    our answers upon. if the company wants
    to hurry through the sealing will be minimal.
    your costs to operate won't.

    best of luck.
    The cure of the part should not be attempted without the cure of the whole. ~Plato

  6. #6
    Join Date
    Nov 2012
    Posts
    31
    Quote Originally Posted by energy_rater_La View Post
    if it is dirty..you have leakage. return leakage contributes
    to high RH indoors.
    if they don't want to do the work..they will
    say it is ok.

    are they using mastics to seal new supply plenum?
    don't let them duct tape of foil tape the leakage
    it might seal now..but later it will leak.

    we've seen other systems to base
    our answers upon. if the company wants
    to hurry through the sealing will be minimal.
    your costs to operate won't.

    best of luck.
    Name:  IMG_1554.jpg
Views: 194
Size:  79.3 KB

    This is what the coil looks like.
    They are going to mastic and seal all connections. Also the insulation look black because the material was black as somebody suggested. Should it be replaced anyway?

  7. #7
    Join Date
    May 2004
    Location
    south louisiana
    Posts
    3,231
    take a picture of it hard to see from here!
    The cure of the part should not be attempted without the cure of the whole. ~Plato

  8. #8
    Join Date
    Sep 2008
    Location
    Western PA
    Posts
    25,758

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