rooftop a/c units
rooftop a/c units
(OP)
for argument sake, let's say that I have a 50 ton ac unit mounted on a roof. Center line Spacing between roof trusses(open web steel type) is 24". must the trusses be cut to form a hole for supply & return air plenums or can the plenums fit between the uncut trusses?Let me know what the industry does.thks!!





RE: rooftop a/c units
Plenum & duct above the roof should be minimum 24" above the roof to allow future repair/replacement of the roof. It not possible to elevate, then the whole duct/plenum portion must be within a air & watertight curb structure.
See also detail for streamline section around obstructions, Figure 2-8 page 2-10 1995 edition of SMACNA HVAC Duct Construction Standards Metal & Flexible.
RE: rooftop a/c units
Usually the supply and return connections to rooftop units are much larger than the duct they would connect to. You might be able to blank-off a section of the opening where the truss runs underneath. If the truss runs in the dead center of the opening (usually my luck), you might have to do what lilliput suggested.
RE: rooftop a/c units
RE: rooftop a/c units