installation of EMT 9or FMT) within a curtain wall mullion system

[markjkubicki]

as Architectural Lighting Consultants, we often mount lighting fixtures in "difficult" locations (ex: on the metal mullions of the curtain wall); and to access power to them, the EE often routes conductors through the mullions. However, there seems to be a consistent inconsistency on what is an allowable method:

a) the fully enclosed metal mullion system (usually an aluminum extrusion with a snap-cap) is an acceptable raceway, and insulated conductors (THHN or equivalent) can be pulled thru it without issue provided the mullion system is properly bonded to ground).

b) the mullion system is not an acceptable raceway, and the cable must be enclosed within its own raceway (EMT, FMT, <etc.> )

c) the mullion system is not an acceptable raceway, and the cable must be enclosed within a RIDGID conduit (FMT is NOT acceptable) regardless of the length of the run; this is particularly problematic in that the often necessary flexibility to route thru bends... is not possible

d) power CANNOT be run thru architectural mullions (period)

Your thoughts would be greatly appreciated in advance,
Mark Kubicki - Tillotson Design

 

[augie47]

For the OPs benefit, I added a poll.
(My choice is b)

 

[iwire]

Put me down as a B.

 

[texie]

I think I'm inclined to vote "B" as well as I don't think that by any stretch the mullion could be considered a compliant raceway. But maybe under certain conditions, with particular attention paid to the entry and exit details of the conductors, this may be acceptable practice if only the code would allow it. Maybe a code change proposal is in order. After all we do something similar in outdoor lighting where the pole is allowed as a raceway with certain conditions.
I might add that this is a common practice for Class 2 circuits for things such as building access controls.

 

[ActionDave]

I'm voting for B also. I see no issue if romex, or MC is used.

 

[Cow]

. After all we do something similar in outdoor lighting where the pole is allowed as a raceway with certain conditions.

It almost sounds like these aluminum raceways with snap covers are similar to the aluminum channel wiring compartment used for automatic doors in supermarket entrances.