Talking to another electrician today who works in another area.
He tells me there is an inspector in this area, who says, when using NM in a commercial building, the NM in attics and basements must be enclosed on both sides, within 15 minute finish rating in living area and attic or basement area.
He said the inspector is using (twisting in my oppinion) the wording of 334.10(3).
I proceeded to tell him I was glad we do zilch in NM work and don't work in this area.
After thinking about it,I thought I would see what oppinions would come up here.
Why on both sides? Doesn't 1/2" sheetrock provide a 15 minute rating? Or is it 3/4"? Either way, if this rated material meets the requirement of a 15 minute barrier, anything on the other side has no effect.
Clue me in guys: Quote from above: "He tells me there is an inspector in this area, who says, when using NM in a commercial building, the NM in attics and basements must be enclosed on both sides, within 15 minute finish rating in living area and attic or basement area."
Are we saying above that the ceilings must be 15 min. fire rated: and the "floors have to be 15 min fire rated also??
Or to put it another way: OPen joist ceilings, or attic floors CANNOT have NMC wiring???
1/2" sheetrock is at least a 15 min fire rating. 2 layers of 5/8" make a 1 hour wall I believe. Tommorow, I have to ask the Building Inspector, and the Electric Sub-Code Official (Head Inspector) for clarifications.
I am reading the IAEI "Analysis of the 2002 NEC" book and on page 185 in reference to 334.10 it says "Type NM, Type NMC and Type NMS cables shall be permitted to be used in the following:
(1) One- and Two-family dwellings.
(2) Multifamily dwellings permitted to be of Types III, IV, and V construction except as prohibited in 334.12
(3) Other structures permitted to be of Types III, IV, and Type V construction except as prohibitied in 334.12. Cables shall be concealed within walls, floors or ceilings that provide a thermal barrier of material that has at least a 15-minute rating as identified in listings of fire-rated assemblies."