Branching Off A Main...

[CuriouslyGeorge]

I forget...what is the rec'd minimum tolerance to leave when cutting a branch duct into a main? Assume cutting a rectangular duct into a rectangular duct. Hmm, what about a small circular duct cut into a duct of larger diameter?

I believe you must maintain a 2" minimum tolerance correct? If a 4x6 branch is being cut into the side of a main, the main must be at least 10 inches deep, correct? This accounts for 2" above and below the branch, right?
C.George

 

[CuriouslyGeorge]

I bet it's 1" tolerance to maintain on each side...2" total! That seems to make more sense. Maybe someone can confirm?

Thanks,
CuriouslyGeorge

 

[cme]

I spec Buckley corp products

Bellmouth for taps to vav and cv boxes

They make rectangular heel taps and oval taps too

They come with an adhesive gasket and holes for sheetmetal screws to secure to the main duct

For taps to diffusers I spec Buckley AMTD, same gasket, etc

united mcgill also makes conical taps

it all depends upon the product

 

[CountOlaf]

George,

Yes, the second thing you said. 2" total.

You might have to have a smaller branch if you use something like a conical fitting because it tapers down to the branch size. For instance, an 8" branch off of a 10" main is acceptable, but the conical fitting OD might be close to 10" so it might not work.

 

[quark]

2" should not be hard and fast but it depends upon the branch section flange overlap. Generally we go with 1" flange overlaps near branch take offs and that is why keep 10 to 15mm gap on each side.

Regards,