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SMACNA Duct question - duct shaft

dfrudfru Posts: 26Member
We have a large concrete makeup air shaft on a project. The shaft will be lined with sheet metal. The contractor is saying that the duct will be 4" smaller on each side to account for flanges and other "space" that they need. We would therefore lose 8" of duct space in the shaft. Does SMACNA have an approved way to line the shaft with sheet metal to avoid the flanges and other space otherwise needed?


  • HVACNUTHVACNUT Posts: 2,768Member
    Not that I'd have an answer anyway but you left out some pertinent information. What are the existing dimensions of the shaft? Why is makeup air needed and how much makeup air is needed?
    Dropping sections of ductwork down a vertical shaft will certainly need Ductmate joint connections. No slips and drives here. The Ductmate joint connections will add about 3 inches to the width and depth. Any requirements on the metal? Galvanized or stainless? 24 ga. 22 ga.?
  • dfrudfru Posts: 26Member
    Thanks HVACNUT,

    The duct is 96" × 96". Galvanized steel. Low velocity makeup air. 600 fpm.

    What about flanged ends? 1/2"? Or welded (we would have to regalvanize the welded efrom. Can the she metal be pinned to the inside surface of the shaft?
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