200.4(B) Neutral Conductors. Multiple Circuits.
Code Change Summary: A new subsection was added requiring identification of multiple neutral conductors in the same enclosure.
A new subsection now requires the grounded neutral conductor of a circuit to be identified or grouped to correspond with the associated ungrounded circuit conductors. The grouping must be done by wire markers, cable ties, or similar means in at least one location within the enclosure.
This requirement applies to any enclosure where more than one neutral and more than one circuit exists. This means junction boxes, panelboards, disconnect switches and the like. Any time there is more than one grounded neutral conductor present in the same enclosure with ungrounded conductors of other circuits, grouping or identification is needed in order to know which circuit each grounded neutral serves.
When troubleshooting or tying into existing circuits, it can be difficult to know which neutral to use. Generally, neutral conductors are not disconnected by the circuit breaker where the branch circuit originates. This can often result in the roll of a dice to decide which neutral to tie into in a junction box downstream of the circuit breaker.
Opening a neutral under load can result in electric shock. If the circuit arrangement is evident, then when a circuit is switched off for servicing, the electrician can remove a wire nut for a group of neutrals and be assured that there is no return current flowing when the wire nuts are removed.
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).
2014 Code Language:
200.4(B) Multiple Circuits. Where more than one neutral conductor associated with different circuits is in an enclosure, grounded circuit conductors of each circuit shall be identified or grouped to correspond with the ungrounded circuit conductor(s) by wire markers, cable ties, or similar means in at least one location within the enclosure.
Exception No. 1: The requirement for grouping or identifying shall not apply if the branch-circuit or feeder conductors enter from a cable or a raceway unique to the circuit that makes the grouping obvious.
Exception No. 2: The requirement for grouping or identifying shall not apply where branch-circuit conductors pass through a box or conduit body without a loop as described in 314.16(B)(1) or without a splice or termination.