Riser listed cable in EMT for run through Plenum ?

[11Haze29]

I'm running some fiber optic from outdoors to indoors. I need to go above a suspended ceiling (plenum) that is used for return air handling. Run will be more than 50ft.

770.2 Definitions, point of entrance ....from rigid metal conduit...
So if I used rigid conduit through the space I could use unlisted cable.

770.113(C) Other spaces used for environemental air (plenums). (4) OFNR, OFCR (which is riser rated) installed raceways that are installed in compliance to 300.22(C)

300.22 (C) (1) Wiring methods ...Other types of cables... shall be permitted to be installed in EMT...

This seems to tell me that if I specify Riser rated cable, I can run it through the plenum, if it is installed in EMT.

Bit tricky understanding this, so I am asking if the above is correct? Comments welcomed.

 

[Smart $]

I'm running some fiber optic from outdoors to indoors. I need to go above a suspended ceiling (plenum) that is used for return air handling. Run will be more than 50ft.

770.2 Definitions, point of entrance ....from rigid metal conduit...
So if I used rigid conduit through the space I could use unlisted cable.

I don't think that is the intent of the definition, i.e. cable is considered outside the building if run in RMC/IMC. I think those are there for when there is no wall or slab floor. But I'll agree it does leave it open to interpretation.

However, 770.48 will prevent you from doing so because it says "in building spaces, other than risers, ducts used for environmental air, plenums used for environmental air, and other spaces used for environmental air"... so the measurement from the point of entrance is moot in your case.

770.113(C) Other spaces used for environemental air (plenums). (4) OFNR, OFCR (which is riser rated) installed raceways that are installed in compliance to 300.22(C)

300.22 (C) (1) Wiring methods ...Other types of cables... shall be permitted to be installed in EMT...

This seems to tell me that if I specify Riser rated cable, I can run it through the plenum, if it is installed in EMT.

That is correct.

 

[cowboyjwc]

Or you could just use plenum rated cable.

 

[Smart $]

Or you could just use plenum rated cable.

That too... Types OFNP and OFCP are rated for both plenum and riser uses without raceway.

 

[11Haze29]

I would use plenum rated cable if it were available. In this case I need 96 strands and Corning only goes up to 72 strands in plenum rated, but they go up to 144 in riser rated.

 

[five.five-six]

Seems Corning has 144 strand in multimode fiber, you could always run 2 48 strand cables if you need single mode. I would absolutely run it in plenum rated innerduct.