Code Change Summary: A new code section makes it clear that specific emergency circuits cannot be supplied from a multiwire branch circuit.

The new code section specifies that branch circuits serving emergency lighting and power circuits shall not be part of a multiwire branch circuit. This code change is all about ensuring continued operation and reliability.

Emergency circuits provide limited power and emergency lighting so that occupants can safely egress the building during an emergency. In a multiwire branch circuit, two or three ungrounded circuit conductors are terminated to the same breaker with a common handle tie. In the event that the electrician needs to service one of the ungrounded circuit conductors, all conductors landed on that breaker will be disconnected when it is switched off. Any time emergency circuits are disconnected, those emergency systems are temporarily offline which can create a potential hazard.

Not allowing emergency power and lighting circuits to be part of a multiwire branch circuit will create a safer situation for building occupants.

Below is a preview of the NEC^®.  See the actual NEC^® text at NFPA.ORG for the complete code section. Once there, click on the “free access” tab and select the applicable year of NFPA 70 (National Electrical code).