Roof Top HVAC Equipment
Roof Top HVAC Equipment
(OP)
I am unclear on a note on structural drawings. I have to place two HVAC units on the roof and the drawings state the following- The roof framing design includes one or sum of roof supported mechanical unit(s) weighing no more than 1,500 lbs. supported by at least two joists per bay. (adjacent bay loading pattern is not considered) Heavier unit(s) require additional structural analysis. What does the adjacent bay loading pattern statement mean (looking for a simple opinion). I take it the unit has to be supported by the joists correct? See pic attached, but what is the meaning of the adjacent bay loading statement?
Thank you for your opinion!
Thank you for your opinion!






RE: Roof Top HVAC Equipment
RE: Roof Top HVAC Equipment
Mike McCann, PE, SE (WA)
RE: Roof Top HVAC Equipment
RE: Roof Top HVAC Equipment
If the curb won't span the distance, provide supplementary structural reinforcement under the metal deck to transfer the load to the joists.
RE: Roof Top HVAC Equipment
RE: Roof Top HVAC Equipment
Jim
RE: Roof Top HVAC Equipment
RE: Roof Top HVAC Equipment
RE: Roof Top HVAC Equipment
I agree that the note writer meant any bay could take one RTU, but the note writer must specify how close together the RTU's can be located. We often say each bay of a craneway can support One (1) design crane load but we also add that the cranes must be installed with a stand-off or a distance limiter must be installed that prevents the individual crane loads from being closer together than one bay lengths distance. In theses cases we say the craneway must be simple span crane beams not continuous 2 bay or more crane beams.
Jim
RE: Roof Top HVAC Equipment
RE: Roof Top HVAC Equipment
I agree that you definitely need to go to the engineer of record for clarification in writing!
I think, but, hey, it's just my interpretation, and I am likely as wrong as anyone else,
I think a pair of joists was designed to support 1500 lbs between them, whether that 1500 lbs is composed of a single 1500 unit or perhaps (3) 500 lbs units, but a total of 1500 lbs max.
I think by "bay" he means joist bay and not girder or column bay... (but, hey there's definitely problems with my interpretation too), and that the note is saying an additional unit cannot be placed in the adjacent joist bay such that the middle joist of the two joist bays is overloaded.
RE: Roof Top HVAC Equipment
One employer of mine lost 22 units before finding a cage that was sturdy enough.
Mike Halloran
Pembroke Pines, FL, USA
RE: Roof Top HVAC Equipment
RE: Roof Top HVAC Equipment
RE: Roof Top HVAC Equipment
https://search.yahoo.com/yhs/search?p=air+conditio...
Mike Halloran
Pembroke Pines, FL, USA
RE: Roof Top HVAC Equipment
Mike McCann, PE, SE (WA)
RE: Roof Top HVAC Equipment
Mike Halloran
Pembroke Pines, FL, USA