Fire-rated emergency feeders

[Junior_EE]

Our state follows the 2023 version of the NEC. We need to 2-hour rate our emergency feeders. Here is the relevant code section on doing so, from our version of 700.10(D):

(1) Feeder-Circuit Wiring​

Feeder-circuit wiring shall meet one of the following conditions:

1. The cable or raceway is installed in spaces or areas that are fully protected by an approved automatic fire protection system.
2. The cable or raceway is protected by a listed electrical circuit protective system with a minimum 2-hour fire rating.
   Informational Note No. 1: See UL 1724, Fire Tests for Electrical Circuit Protection Systems, for one method of defining an electrical circuit protective system. The UL Guide Information for Electrical Circuit Integrity Systems (FHIT) contains information to identify the system and its installation limitations to maintain a minimum 2-hour fire-resistive rating and is available from the certification body.
3. The cable or raceway is a listed fire-resistive cable system with a minimum 2-hour fire rating.
   Informational Note No. 2: See UL 2196-2017, Standard for Fire Test for Circuit Integrity of Fire-Resistive Power, Instrumentation, Control and Data Cables, for one method of defining a fire-resistive cable system.
4. The cable or raceway is protected by a listed fire-rated assembly that has a minimum fire rating of 2 hours and contains only emergency circuits.
5. The cable or raceway is encased in a minimum of 50 mm (2 in.) of concrete.

If we run the feeder outside of the building, can the building itself be considered a listed fire-rated assembly? As in, can we simply run regular EMT and conductors outside of the building? For various reasons, we cannot run inside the building. The building is mostly masonry block for the exterior.

 

[infinity]

I don't see outside of the building on that list of acceptable wiring methods. The building doesn't have sprinklers per condition 1?

 

[Junior_EE]

I don't see outside of the building on that list of acceptable wiring methods. The building doesn't have sprinklers per condition 1?

We cannot run inside the building. Our belief is that the exterior of the building itself is considered a fire-rated assembly (#4), similar to running regular conduit/wire inside of a 2hr-rated room within the building.

 

[infinity]

We cannot run inside the building. Our belief is that the exterior of the building itself is considered a fire-rated assembly (#4), similar to running regular conduit/wire inside of a 2hr-rated room within the building.

That sounds like a stretch but if you can find something in the building code that says "that the exterior of the building itself is considered a fire-rated assembly" go for it. And what is the reason you cannot run inside the building?

 

[don_resqcapt19]

I don't see outside of the building on that list of acceptable wiring methods. The building doesn't have sprinklers per condition 1?

Most the time, the wiring method, even in a structure with sprinkler protection, is not installed in an area that actually has sprinkler protection. The wiring is typically installed in a concealed space, and few concealed spaces are fully protected by a fire sprinkler system.