MEP Question: Routing of electrical for rooftop kitchen fan

[brycenesbitt]

I'm not sure exactly where to start here. Is it acceptable to route electrical wires for a rooftop kitchen vent fan,
through the exhaust duct? If so is conduit sufficient?
If not, what rule prevents such an installation?

In this case running through the vent would reduce the number of roof penetrations that have to be sealed, and make for a neater installation
without wires exposed to the UV on the roof.

What forum would best be used to answer such a question, and get a code citation that a City inspector might accept?

 

[mtnelect]

Section 300.22(A)

 

[LarryFine]

Are you talking about a commercial or residential kitchen?

 

[brycenesbitt]

Are you talking about a commercial or residential kitchen?

Residential kitchen, on the 2019 code cycle in California (CRC roughly corresponds to the UPC and NEC).

This is specifically for the control wiring and or a rooftop fan, servicing a cooking grease hood located directly below.
Specifically the rooftop fan is to have a humidity sensor, and turn on when cooking activities below create humid air.
FOG of course would end up coating the conduit.

The goal is to reduce the number of metal roof penetrations. I could run the conduit on the outside of the range hood duct, but that complicates the boot at the metal roof.

Based on @mtnelect I see this complicated related topic:

Understanding Environmental Air Spaces and Section 300.22(C) and Type MC Cable.

Is Metal-Clad Cable “Plenum” Rated? NEC Section 300.21 provides clarification to the intend of why the concern about ratings of raceways or cables assemblies for electrical installations in hollow spaces, vertical shafts, and ventilation or air-handling ducts be made so the possible spread of fire o

www.linkedin.com

 

[LarryFine]

Sounds more like a typical commercial-kitchen exhaust-fan installation.

I usually run MC cable outside the duct, up into the roof curb, through my own hole in the top or side of the curb, and transition to a watertight flex to the fan's disconnect.

I would really have to see pictures of your fan, both underneath and up top, to give more specific advice.

 

[mtnelect]

Residential kitchen, on the 2019 code cycle in California (CRC roughly corresponds to the UPC and NEC).

This is specifically for the control wiring and or a rooftop fan, servicing a cooking grease hood located directly below.
Specifically the rooftop fan is to have a humidity sensor, and turn on when cooking activities below create humid air.
FOG of course would end up coating the conduit.

The goal is to reduce the number of metal roof penetrations. I could run the conduit on the outside of the range hood duct, but that complicates the boot at the metal roof.

Based on @mtnelect I see this complicated related topic:

Understanding Environmental Air Spaces and Section 300.22(C) and Type MC Cable.

Is Metal-Clad Cable “Plenum” Rated? NEC Section 300.21 provides clarification to the intend of why the concern about ratings of raceways or cables assemblies for electrical installations in hollow spaces, vertical shafts, and ventilation or air-handling ducts be made so the possible spread of fire o

www.linkedin.com

I agree with LarryFine Environmental Air is permitted, but anything else it has to be outside the duct system.

 

[brycenesbitt]

I would really have to see pictures of your fan, both underneath and up top, to give more specific advice.

It's new build, so no pictures exist. There's a passive range hood below, a duct to the roof decking. The roof has decking, 4" of solid foam, a second deck, then standing seam metal.

Yes, its meant to be set up like a commercial kitchen exhaust fan. The fan itself has yet to be selected, seeking something that's super quiet, and probably going to rubber isolate the curb. A square fan for a square curb would be idea, if the wire can come up one corner.

 

[mtnelect]

It's new build, so no pictures exist. There's a passive range hood below, a duct to the roof decking. The roof has decking, 4" of solid foam, a second deck, then standing seam metal.

Yes, its meant to be set up like a commercial kitchen exhaust fan. The fan itself has yet to be selected, seeking something that's super quiet, and probably going to rubber isolate the curb. A square fan for a square curb would be idea, if the wire can come up one corner.

If this project is in California, make sure that it meets Title 24 requirements.