Plenum space definition

[nhfire77]

Imagine a retail store with an open ceiling to the roof. There are RTU's on the roof. There are supply and return ducts around the space at the bottom of the bar joist.

Is this entire area a plenum space, requiring plenum rated cable?


I'm confused, some say yes some no. I believe this discussion has taken place here, but couldn't find it.

 

[cowboyjwc]

If there are return ducts run down to grills in the ceiling, then it is not a plenum.

 

[zbang]

A search for "environmental air" turns up many hits, but IIRC the answer was "it depends". If there is no "ceiling" then it's just ducts hanging from the roof. Keep the cables out of those ducts .

 

[nhfire77]

There is no drop ceiling. Its supply and return vents all at 13'AFF, above the vents is the roof, below is the floor

 

[nhfire77]

A search for "environmental air" turns up many hits, but IIRC the answer was "it depends". If there is no "ceiling" then it's just ducts hanging from the roof. Keep the cables out of those ducts .

Thats my problem. There are plans engineered and architect designed plans, but not for my scope of work, I define my scope and materials. Someone is attempting to make it an issue.

It appears the electrical inspector may not care, but I don't want to address it with him until I have facts. If, I can find other places that side with my opinion, factually based of course, it won't be an issue.

Again, it depends.

 

[steve66]

300.22(C) seems pretty clear to me. The last sentance: "It does not include habitable rooms, or areas of buildings, the prime purpose of which is not air handling"

I don't believe the plenum cable is required.

 

[raider1]

I agree with Steve, not a plenum.

Chris

 

[nhfire77]

300.22(C) seems pretty clear to me. The last sentance: "It does not include habitable rooms, or areas of buildings, the prime purpose of which is not air handling"

I don't believe the plenum cable is required.

I read that section too fast, good point. Thank you!

 

[fmtjfw]

Make sure the inspector is not going to treat it as "a place of public assembly". We've been told plenum cable only and metallic sheathed cables or metallic conduit in open spaces in school building which they treat the "whole" building as a place of public assembly.

 

[raider1]

Make sure the inspector is not going to treat it as "a place of public assembly". We've been told plenum cable only and metallic sheathed cables or metallic conduit in open spaces in school building which they treat the "whole" building as a place of public assembly.

518.4 Exception would not require plenum rated cables for communications, Class 2 or 3 circuits, fire alarm or audio systems.

Chris

 

[fmtjfw]

I have a few rules of life that I follow:

1. Never pass a moving police car with it lights flashing and siren on.
2. Never pick a fight with a state fire marshal.

Rule number 2 applies to plenum rated cable in a school building.

 

[nhfire77]

I have a few rules of life that I follow:

1. Never pass a moving police car with it lights flashing and siren on.
2. Never pick a fight with a state fire marshal.

Rule number 2 applies to plenum rated cable in a school building.

I get that.

The EI agrees, if that was a plenum space, then any space not completely air sealed could be argued a plenum, even in a wall if air could be drawn through it. He added, then you wouldn't even have non plenum. The fire department defers to him on NEC issues.

I think the other guy was trying to tell my crew so we wouldn't have to replace it. I'm going to talk with them, I've heard certain EI's in the area just demand it and they do it.