Can emergency circuits share a raceway with normal power?

No. NEC 700.10(B) requires emergency wiring to be kept entirely independent of all other wiring and prohibits it from entering the same raceway, cable, box, or cabinet, apart from a short list of exceptions.

Do legally required standby circuits follow the same rule?

No. Article 701 for legally required standby systems is more permissive than Article 700 on raceway sharing, so verify which article applies before designing the raceway layout.

Can I put normal 277 volt power and emergency power in the same conduit?

Q: Where are emergency and normal wiring allowed to share an enclosure?

In transfer equipment enclosures, in luminaires supplied from two sources, in a common junction box attached to those luminaires, and in boxes or enclosures where the emergency supply conductors enter, per NEC 700.10(B).

No. Article 700 treats emergency circuits as a separate system that has to survive the failure of the normal system, and sharing a raceway defeats that. This is one of the rules inspectors and commissioning agents check first on a life safety job.

What 700.10(B) requires

Section 700.10(B) of the 2023 NEC states that emergency wiring shall be kept entirely independent of all other wiring and equipment, and shall not enter the same raceway, cable, box, or cabinet as other wiring. The word entirely does a lot of work there. It covers the raceway, the cable, the box, and the cabinet, so you cannot solve it by keeping the conductors on opposite sides of a pull box.

The permitted exceptions are narrow. Emergency wiring may occupy the same enclosure as other wiring in transfer equipment enclosures, in luminaires supplied from two sources, in a common junction box attached to those luminaires, and in boxes or enclosures where emergency circuits enter as required for the source of supply to the emergency circuits. That is the list. A general purpose junction box on a corridor lighting run is not on it.

Why this rule exists

A fault, a fire, or a mechanical strike that takes out the normal feeder should not take the egress lighting with it. Section 700.10(D) goes further for occupancies over a certain size, requiring feeder circuit wiring for emergency systems to be protected by 2 hour fire rated assemblies, embedded in concrete, or installed as a listed electrical circuit protective system. If the emergency conductors were riding in the same pipe as normal power, none of that protection would matter.

Article 701 for legally required standby systems is more permissive on this specific point, so do not carry an Article 700 habit into an Article 701 design or the reverse. Article 517 imposes its own rules in health care facilities, where 517.31 governs separation of the life safety, critical, and equipment branches of the essential electrical system, and those branches must also be kept independent of each other.

Practical field consequences

Plan for the extra raceway at layout, not at trim. Emergency lighting home runs get their own pipe from the panel, and a two source luminaire is where the two systems are finally allowed to meet. Section 700.10(A) requires emergency circuit boxes and enclosures to be permanently marked so they are readily identified as part of the emergency system, so label the pull boxes and the raceway as you go rather than after the ceiling closes.

Section 700.5 and 700.12 cover the source and transfer equipment, and 700.10(B)(5) is the exception that lets the two systems meet inside the transfer switch. Anything outside those enclosures stays separated. If a shared conduit already exists on a job, the fix is a new raceway, not a divider or a barrier, because 700.10(B) does not offer a barrier option.

Field takeaway

Emergency stays in its own pipe, its own boxes, and its own panel. The only places the two systems legally share space are transfer equipment, two source luminaires and the junction box attached to them, and the enclosure where the emergency supply enters. Mark the emergency raceway and boxes as required by 700.10(A).