Article 330.22 (C) exception

Status
Not open for further replies.
G

Garth Grob

Member
Location
Vermilion, Ohio
Is non-metalic NM cable permitted to run through the cold air return space un-protected, or should it have a metal raceway to cover it? The N.E.C. handbook is non-specific as to what type of cable is permitted, but does show a diagram with the cable installed. No where does it specify Plenum rated cable. This practice seems common in residential wiring. (Inspectors I have delt with in the past never permitted any wiring to pass through cold air returns, unless it was encased in emt.)
 
I think that you meant 300.2(C). Yes, NM cable can through a stud space if run perpendicular to the studs.


Welcome to the Forum. :)

300.22(C)Exception: This section shall not apply to the joist or stud
spaces of dwelling units where the wiring passes through
such spaces perpendicular to the long dimension of such
spaces.
Click to expand...
 
infinity said:
NM cable 90? C or 194? F. In reality would that matter?
Click to expand...
Depends on whether the current in the wire is high enough to cause problems with derating for ambient temperature, I guess. Probably not. You would be going through tin and not just wood, so a bushing would be in order.
But in terms of plenum wiring requirements, the hot air duct delivers air directly to occupied spaces, rather than to a return plenum where you could potentially have a smoke detector.
 
Article 300.22 (C)

Article 300.22 (C)

How can an inspector prove that any romex is considered a permitted cable? The exception only states that this section does not apply. (Then what does?) The handbook states cable is permitted to run throught the plenum space between studs. But does not specify what type of cable is permitted. Is the inspector to assume that any type of cable is permitted? Then what is the point of a plenum rated cable?
 
Garth Grob said:
How can an inspector prove that any romex is considered a permitted cable? The exception only states that this section does not apply. (Then what does?) The handbook states cable is permitted to run throught the plenum space between studs. But does not specify what type of cable is permitted. Is the inspector to assume that any type of cable is permitted? Then what is the point of a plenum rated cable?
Click to expand...
The intent of the exception pretty clearly (to me at least) appears to be to allow "incidental" or minimal presence of non-plenum cable and wiring methods inside that specific type of plenum space.
 
Garth Grob said:
Is non-metalic NM cable permitted to run through the cold air return space un-protected, or should it have a metal raceway to cover it? The N.E.C. handbook is non-specific as to what type of cable is permitted, but does show a diagram with the cable installed. No where does it specify Plenum rated cable. This practice seems common in residential wiring. (Inspectors I have delt with in the past never permitted any wiring to pass through cold air returns, unless it was encased in emt.)
Click to expand...

yes by exception, 300,22(C) "shall not apply" for residential dwelling units for wiring passing perpendicular through the stud or joist space.

The exception applies to spaces that are created by covering one or two sides of the joist or stud space with sheet metal, wiring entering and exiting through holes in the wood. It does not apply to duct spaces, passing through the sheet metal. If you are passing though the duct, you need a plenum rated method

300.22(C), other space used for environmental air, wiring methods shall be limited to ... intends to limit smoke transmission to other occupied spaces by prohibiting combustible or smoke producing products and methods from that space. It also assumes the plenum or other air handling space is itself built of non combustible products. The residential joist space would itself be built of combustible products, and the exception applies. But a duct in the joist space would fall under 300.22(B) and the exception would not apply.

The romex never passes through a ducted or plenum space, it is allowed by exception to pass through an "other space used for environmental air", compliant with the exception.
 
Last edited:
Dan said it nicely. :)

Basically it's permitted if done to limit the length of cable through the space.
 
Status
Not open for further replies.
Top