NM in a commercial setting.

[tchutson]

We are starting a roughly 10,000 sq ft daycare. It is single story wood frame construction on a concrete slab. We are running NM in the building. A fellow contractor came by during lunch when no one was there and called our company to say that once we penetrated the top plate of the walls we had to transition to MC in the attic space. I am unable to find anything that may suggest that is true and would like to know if we need to change anything. Thanks in advance for your help

 

[Little Bill]

We are starting a roughly 10,000 sq ft daycare. It is single story wood frame construction on a concrete slab. We are running NM in the building. A fellow contractor came by during lunch when no one was there and called our company to say that once we penetrated the top plate of the walls we had to transition to MC in the attic space. I am unable to find anything that may suggest that is true and would like to know if we need to change anything. Thanks in advance for your help

You would only need to change to a different wiring method above the ceiling if there was going to be a dropped ceiling. Otherwise, NM would be allowed. Only other thing would be the construction type the building is permitted for.

 

[mtnelect]

Electrical Wiring - Residential, cable.

 

[mtnelect]

Electrical Wiring - Residential, bored holes.

 

[Little Bill]

Electrical Wiring - Residential, cable.

Electrical Wiring - Residential, bored holes.

What do either of these have to do with the OP's question? If there is something in the PDFs about the question, I didn't see it.

 

[Joe Villani]

I think it's the 15 minute finish rating that isn't present in the attic that the other contractor in the OP is referring to.

 

[Fred B]

I think it's the 15 minute finish rating that isn't present in the attic that the other contractor in the OP is referring to.

334.10(3)

 

[Little Bill]

I think it's the 15 minute finish rating that isn't present in the attic that the other contractor in the OP is referring to.

334.10(3)

The ceiling could/should provide the 15 min finish rating. Nothing in the attic is required to except the ceiling below.

 

[Fred B]

Also did have come across that building code not NEC that was supposedly requiring MC in attic space according to building inspector.

 

[Joe Villani]

What is the rational for exempting the attic from 334.10(3)?

I would think the attic is part of the structure?

 

[drcampbell]

You would only need to change to a different wiring method above the ceiling if there was going to be a dropped ceiling. ...

If I understand correctly, that's only if the space above the dropped ceiling is used for a return-air plenum.
(does plenum-rated NM cable exist?)

 

[Joe Villani]

I would also say to the OP if the attic has no access the NM would be fine.

 

[mtnelect]

What do either of these have to do with the OP's question? If there is something in the PDFs about the question, I didn't see it.

This additional protection is not required when the raceway is intermediate metal conduit (Article 345), rigid metal conduit (Article 346), rigid nonmetallic conduit (Article 347), or electrical metallic tubing (Article 348), Figure 4-26.

Section 334.15 restricts the use of Nonmetallic-Sheathed Cable, when not concealed. The attachment is based on 1999 NEC, but the intent hasn't changed.

 

[Little Bill]

Also did have come across that building code not NEC that was supposedly requiring MC in attic space according to building inspector.

Please read what you wrote here and clarify. I can't understand it.

 

[Little Bill]

If I understand correctly, that's only if the space above the dropped ceiling is used for a return-air plenum.
(does plenum-rated NM cable exist?)

You can't have NM cable above a dropped ceiling in a non-dwelling.

 

[mtnelect]

You can't have NM cable above a dropped ceiling in a non-dwelling.

If you install NM cable in an attic you have to provide protection against damage. If you install MC cable you don't.

 

[rc/retired]

If you install NM cable in an attic you have to provide protection against damage. If you install MC cable you don't.

What type of protection from damage is required for NM-B cable is required?
I trust you have a code reference for this.

Ro

 

[mtnelect]

What type of protection from damage is required for NM-B cable is required?
I trust you have a code reference for this.

Ro

Section 334.15 Exposed Work

 

[rc/retired]

Section 334.15 Exposed Work

In an attic? How is that exposed?

 

[mtnelect]

In an attic? How is that exposed?

Section 320.23 In Accessible Attics