See drawing..
The main area is open from floor to roof deck in a concrete and steel building, the ceiling is insulated above the deck. Within this space are offices that will have walls all the way up to the roof deck and dropped tile ceilings (for sound suppression). HVAC distribution is ducted into each office.
Now, to get the return air from the offices back to the open space, the hvac contractor could place grates in the dropped ceiling and another in the sheetrock wall between the office and open space. This would be a plenum space by definition.
However, if the hvac contractor ducted the return from the office to the open area, this should NOT be a plenum space....
My contention is, if the hvac contractor uses short ductwork for the return air from the offices to the open space areas, plenum rated cables would not be required and eliminate altogether the aggravation and cost of plenum wiring requirements.
What do you guys think? It is obvious to me but I've learned what makes sense to me is not always correct in the eyes of the NEC.
View attachment Plenum.pdf
The main area is open from floor to roof deck in a concrete and steel building, the ceiling is insulated above the deck. Within this space are offices that will have walls all the way up to the roof deck and dropped tile ceilings (for sound suppression). HVAC distribution is ducted into each office.
Now, to get the return air from the offices back to the open space, the hvac contractor could place grates in the dropped ceiling and another in the sheetrock wall between the office and open space. This would be a plenum space by definition.
However, if the hvac contractor ducted the return from the office to the open area, this should NOT be a plenum space....
My contention is, if the hvac contractor uses short ductwork for the return air from the offices to the open space areas, plenum rated cables would not be required and eliminate altogether the aggravation and cost of plenum wiring requirements.
What do you guys think? It is obvious to me but I've learned what makes sense to me is not always correct in the eyes of the NEC.
View attachment Plenum.pdf
