Joeyg61
New member
- Location
- Los Angeles, CA. USA
Other than using IMC or GRC, is there a way around 300.4 (E)
300.4 (E)
- Thread starter Joeyg61
- Start date
- Status
- Location
- New Jersey
- Occupation
- Journeyman Electrician
Nope. Not one of my favorite code sections. :roll:
mwm1752
Senior Member
- Location
- Aspen, Colo
Just to clarify -- roof decking would be part of the thermal envelope -- a floor/ceiling deck is different. Out of the box thinking how would the forum think about using a section of GRC/IMC sleeve for protection? of course once past the sleeve the raceway/cable would drop for compliance.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
In theory that would work for a cable but not a raceway like EMT (unless you could bend the EMT inside of the RMC or IMC). Code wise it's still not compliant because there is no allowance to protect other wiring methods with RMC or IMC.
mwm1752
Senior Member
- Location
- Aspen, Colo
IMO Your comments have conflicting meaning with code statements - seems RMC & IMC are not subject to protection against physical damage when applied to 300.4(E) so why are short sections not allowed to to provide protection for cable assemblies as per 300.10?
300.10 Electrical Continuity of Metal Raceways and Enclosures
Exception No. 1: Short sections of raceways used to provide support or protection of cable assemblies from physical damage shall not be required to be made electrically continuous.
300.4 Protection Against Physical Damage
Where subject to physical damage, conductors, raceways, and cables shall be protected.
(E) Cables, Raceways, or Boxes Installed in or Under Roof Decking.
A cable, raceway, or box, installed in exposed or concealed locations under metal-corrugated sheet roof decking, shall be installed and supported so there is not less than 38 mm (1? in.) measured from the lowest surface of the roof decking to the top of the cable, raceway, or box. A cable, raceway, or box shall not be installed in concealed locations in metal-corrugated, sheet decking?type roof.
Exception: Rigid metal conduit and intermediate metal conduit shall not be required to comply with 300.4(E).
- Location
- New Jersey
- Occupation
- Journeyman Electrician
Although I agree with your logic I don't see where this section says that you can simply use a short piece of RMC or IMC to protect conductors, raceways or cables. It states explicitly that they need to be 1.5" below the lowest part of the roof decking. If you use RMC or IMC as a wiring method then the exception would apply.
Carultch
Senior Member
- Location
- Massachusetts
I suppose you could put in a steel plate, that is equivalent to IMC or GRC.
The intent of this section is to keep nails from being driven in to the conduit. Anything other than IMC or GRC would not prevent this physical damage.
mwm1752
Senior Member
- Location
- Aspen, Colo
I also understand your point of the distinction of not installing any wiring method other than RMC or IMC within 1 1/2" of the lowest part of the deck. The NEC does not explicidly call out an exception with the application of protecting cables & so forth. no nail plates
- Location
- New Jersey
- Occupation
- Journeyman Electrician
Yes, those are the actual words of that section but certainly it would make sense to allow short sections of RMC or IMC to protect other wiring methods. For whatever reason the NEC hasn't made that allowance.
- Status