210.5(C)(1) Branch Circuits Supplied from More Than One Nominal Voltage System.
Code Change Summary: Revisions were made to the labeling requirements for branch circuits at a premises where more than one nominal electrical system voltage exists.
The labeling requirements in Section 210.5(C) first appeared in 2005 and apply when a premises has branch circuits supplied from more than one nominal voltage “system”.
For these systems, the revised 2020 code language will require each ungrounded conductor of a branch circuit to be identified by phase or line and voltage class at all termination, connection, and splice points. Previous code language required identification by “phase or line and system” which was confusing.
Before the 2020 changes in this section, branch circuits originating downstream of each separately derived system (most transformers are separately derived systems) were to have identification that was unique from all other separately derived systems at the same premises even if the voltages of the systems were the same. In a large building there may be many separately derived systems which would make it almost impossible for anyone to comply with the rule as previously written. Allowing the branch circuits to be identified by voltage instead of each individual system is much easier to apply.
A new commercial building may have 277/480-volt electrical panelboards and 120/208-volt panelboards. In this situation, the premises will have branch circuits supplied by more than one nominal voltage system.
Aside from identifying all branch circuits at each termination, connection, and splice point, the 277/480-volt panelboards and the 120/208-volt panelboards will also require identification. Any service electrician should be able to walk up to any panelboard, see the labeling (in the image) and instantly know that the 277/480-volt conductors are brown, orange, yellow, and the 120/208-volt conductors are black, red, and blue.
Below is a preview of the NEC®. See the actual NEC® text at NFPA.ORG for the complete code section. Once there, click on their link to free access to the 2020 NEC® edition of NFPA 70.
2017 Code Language:
210.5(C)(1) Branch Circuits Supplied from More Than One Nominal Voltage System. Where the premises wiring system has branch circuits supplied from more than one nominal voltage system, each ungrounded conductor of a branch circuit shall be identified by phase or line and system at all termination, connection, and splice points in compliance with 210.5(C)(1)(a) and (b).
(a) Means of Identification. The means of identification shall be permitted to be by separate color coding, marking tape, tagging, or other approved means.
(b) Posting of Identification Means. The method utilized for conductors originating within each branch-circuit panelboard or similar branch-circuit distribution equipment shall be documented in a manner that is readily available or shall be permanently posted at each branch-circuit panelboard or similar branch-circuit distribution equipment. The label shall be of sufficient durability to withstand the environment involved and shall not be handwritten.
2020 Code Language:
210.5(C)(1) Branch Circuits Supplied from More Than One Nominal Voltage System. Where the premises wiring system has branch circuits supplied from more than one nominal voltage system, each ungrounded conductor of a branch circuit shall be identified by phase or line and by system voltage class at all termination, connection, and splice points in compliance with 210.5(C)(1)(a) and (b). Different systems within the same premises that have the same system voltage class shall be permitted to use the same identification.
(a) Means of Identification. The means of identification shall be permitted to be by separate color coding, marking tape, tagging, or other approved means.
(b) Posting of Identification Means. The method utilized for conductors originating within each branch-circuit panelboard or similar branch-circuit distribution equipment shall be documented in a manner that is readily available or shall be permanently posted at each branch-circuit panelboard or similar branch-circuit distribution equipment. The label shall be of sufficient durability to withstand the environment involved and shall not be handwritten.
Be sure to refer to the exception in the NEC® for existing installations!!!