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Thread: Ductwork

  1. #1
    Join Date
    Jan 2005
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    Bakersfield, CA
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    209
    I am building a new home (starting in 60 days) and just received a bid from a local Trane contractor. He included 3 options for this split system. One of the options was for a TXV. Through previous information on this site I have decided to include this option (local utility rebate also requires a TXV on this system). The other option is for an April Aire filter system. I'm still trying to decide about this one.

    The last option was for a for something called "Tight Ducts". Not trying to be a smart alec but I assumed all ducts would be tight (not leak, that is). I'm going to call the contractor tomorrow and ask him what "tight ducts" means but I thought I would try to educate myself on the important issues relating to ductwork. Reading many posts on this site has convined me that proper duct work design and installation is one of the most important and often over looked aspects of a good HVAC job. I've also read something about a Manual D(?) calculation relating to duct work.

    What sort of questions should I ask as far as quality ductwork is concerned? What are "Tight Ducts"?

    Thanks very much.

  2. #2
    Join Date
    Feb 2005
    Location
    Kentucky
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    57
    A TXV is better than a cap tube or fixed orfice because it can regulate the freon when the load changes. But really on a low efficient unit you probally would not notice a diff. With a higher efficient unit you would need txv to get the full efficiancy of the unit. As far as the aprilaire filter, I know the aprilaire 5000 was one of the better filters on the market using a media and a electronic together. But the last I heard there was a recall on the media were it could catch on fire, and no replacement media has been sent out yet. The only thing I could think of the tight ducts is the contracter sealing all the duct connections with a duct mastic. With out the duct mastic the duct would not be air tight you would get some leakage.

  3. #3
    Join Date
    Aug 2004
    Location
    Tyler TX
    Posts
    676
    please post a reply on this one. When I install ducts I seal them no other options available. the law here requires it and I would think your laws do to. The only thing I can think of would be flex or hard pipe.

    [Edited by dpatty on 02-13-2005 at 02:49 PM]
    HVAC Contractor, Tyler Texas.

  4. #4
    Join Date
    Feb 2005
    Location
    Kentucky
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    57
    sealing ducts in my area is not a code as of now.

  5. #5
    Join Date
    Jan 2005
    Location
    Bakersfield, CA
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    I'm in Bakersfield, CA. I'll check on the code and also let you know what the contractor says.
    Thanks

  6. #6
    Join Date
    Feb 2003
    Location
    South Carolina
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    1,333
    sealing ducts with mastic is not code but i do it.

  7. #7
    Join Date
    Sep 2002
    Location
    South Dakota
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    6,579


    Duct leakage studies have shown that the typical unsealed residential duct installation leaks 30% or more of the total airflow through the unsealed seams. ACHR News has published the results of at least one of these studies in the past.

    I believe SMACNA has also conducted such a study as well. The results of all the studies indicate that carefully sealing all sheet metal joints makes a great difference.

    I had read that California (California already has its title 24 energy code) was considering adding duct sealing regulations to their installation code.


  8. #8
    Join Date
    Jan 2005
    Location
    Bakersfield, CA
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    Is there more than one way to properly seal the ducts. I seem to remember one writer who advised using mastic and not just tape. So what is the best recommended way? Mastic alone, mastic plus tape?
    Thanks

  9. #9
    Join Date
    May 2004
    Location
    Rapid City, SD
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    7,415
    Mastic is probably the best, and likely would be voted to be the best by the guys here.

    Tape is ok, it does the job, but typically won't last as long as mastic.

    Don't use both though, it wastes time and doesn't improve anything. If the tape falls off so does the mastic.

  10. #10
    Join Date
    Feb 2005
    Location
    Alabama
    Posts
    534
    As far as sealing duct work, if its ductboard I staple all flaps then use foil tape. on "high end" jobs I use #6 mastic over the tape. Only time I've seen it come loose is if the area under the mastic is wet or damp. Also TXV systems are much better than piston or fixed meter types. You'll notice that TXV systems have a much higher SEER rating.

  11. #11
    Are you assuming that duct joints are held in place with sheet metal screws?

  12. #12
    Join Date
    Mar 2005
    Location
    Virginia
    Posts
    1,144
    Originally posted by pipefitter2005
    A TXV is better than a cap tube or fixed orfice because it can regulate the freon when the load changes. But really on a low efficient unit you probally would not notice a diff.
    Any type of expansion valve will drastically improve both efficiency and effectiveness, NO MATTER what the pull it out of their “rear” seer rating the manufacturer is labeling the unit with.

    Freon is a brand... (pet peeve)

  13. #13
    Join Date
    Jun 2004
    Location
    Florida
    Posts
    556
    The Tight ducts might just mean that the ducts have been tested and certified to be leak free. In Florida every house has to have a energy calculation and that calculation gives the house a score. The house has to have a score below 100 to pass. The program that does the calculation has an option for air tight ducts, but when you try to select that option it will tell you that the ducts have to be certified. This comes into play when a house is trying to get a better energy rating. I believe the the house has to get a score of 80 or below to qualify for a reduced interest rate. In addition the rating adds another selling point to the house.

    here is some more info on the ratings.

    http://www.fsec.ucf.edu/bldg/fyh/ratings/

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