Lateral restraint for HVAC Ducts 2

[WARose]

Is there any requirement in a mechanical/HVAC code for HVAC ducts to be laterally restrained? And if so, what is that (spacing) requirement?

I'm structural so our codes really don't address this (beyond loads generated). The (seismic) drift requirements of ASCE 7-10 aren't really applicable to mechanical components. It just says to limit displacements so that drift doesn't "adversely [affect] structural stability or attached or interconnected components".

 

[EnergyProfessional]

SMACNA has standards for everything sheetmetal.

I believe the duct construction standard is what you are looking for most. Sorry, have that at work, but work from home.

 

[WARose]

Thanks EnergyProfessional. I don't have that reference. (And it looks kind of expensive.) Hopefully someone else can tell me (assuming it's a short answer).

 

[DBronson]

WARose:

I believe it is the SMACNA Seismic Restraint Manual that has the details on longitudinal and transverse bracing for piping and duct systems. Unfortunately, I don't have a copy of that document. However, a publication at this Link the Pipe and Duct Application Manual has a discussion of duct bracing (with references to the SMACNA manual) in section S-11.

Regards,
DB

 

[WARose]

Thanks DB.

 

[nuuvox000]

I assume this is for seismic bracing because you mentioned ASCE 7-10 (I believe 7-16 is the adopted version where I live). All straight lengths of duct require seismic bracing. Transverse braces at each end and a longitudinal brace somewhere along the length of the duct run. Note, if the duct is less than 6 square feet in the cross section, then you (as the designed) can exempt it from seismic bracing. We almost always do this unless we think there is a significant risk. Transverse braces can be attached to the duct clevis hanger. Wires (or unistrut) need to come off at 45° and attach to the nearest structure. There are some calcs you have to do that are explained in the ASHRAE seismic guidelines manual but we typically do transverse braces every 30 ft and longitudinal braces every 60 ft.