THHN used in plenum rated ceiling

[Robert Hurd]

I just inspected an existing facility that has THHN insulated green grounding conductors installed in a plenum rated ceiling. The grounding conductors are used as supplemental grounding to building steel. Can a insulated green thhn conductor legally be installed as open wiring in a plenum rated ceiling.

 

[1793]

300.22

300.22

I just inspected an existing facility that has THHN insulated green grounding conductors installed in a plenum rated ceiling. The grounding conductors are used as supplemental grounding to building steel. Can a insulated green thhn conductor legally be installed as open wiring in a plenum rated ceiling.

What size is the conductor?

Look at 250.64(B) and 300.22(C)(1). As I see it this would be a violation.

Edit to include 250.64(B)

 

[Dennis Alwon]

I agree with norb. I talked with a cable manufacturer toay about the insulation on romex. He said it was the same as the insulation on the wire. Basically it was THHN on the jacket of romex. We know that romex cannot be used in a plenum so I would say nay to thhn.

 

[infinity]

I thought that NM cable had a PVC outer jacket?

 

[Robert Hurd]

Norb,

The conductor sizes are thhn insulated #6 and #4. Thanks for your reply.