210.5(C)(1) Branch Circuits Supplied from More Than One Nominal Voltage System.
Code Change Summary: New wording and an exception were added to the labeling requirements for installations on a premises where more than one nominal electrical system voltage exists.
The requirement, which first appeared in the 2011 NEC®, applies when a premises wiring system has branch circuits supplied from more than one nominal voltage system. For these systems, each ungrounded conductor of a branch circuit must be identified by phase or line and system at all termination, connection, and splice points. As well, the identification method utilized must be documented in a way that is readily available or shall be permanently posted at each branch-circuit panelboard or similar branch-circuit distribution equipment.
A good example is a new commercial building with 277/480 volt panelboards and 120/208 volt panelboards. In this situation, the premises will have branch circuits supplied by more than one nominal voltage system.
The 277/480 volt panelboards and the 120/208 volt panelboards will all require identification. A 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.
The 2017 change to this section makes it clear that handwritten labels are NOT allowed. As well, if a new system of a different voltage is being added to an existing installation, the new exception requires only the new installation to be marked with the method used to identify the circuits.
If only the newly installed equipment with the different voltage is identified as the exception allows, other labeling is required at each voltage system distribution equipment to identify that only one voltage system has been marked for only the new system. The new system labels shall include the words “other unidentified systems exist on the premises”.
Below is a preview of Article 210. See the actual NEC® text at NFPA.ORG for the complete code section. Once there, click on their link to free access to the 2017 NEC® edition of NFPA 70.
2014 Code Language:
210.5(C)(1) Branch Circuits Supplied from More Than One Nominal Voltage System. 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.
2017 Code Language:
210.5(C)(1) Branch Circuits Supplied from More Than One Nominal Voltage System. 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.
Exception: In existing installations where a voltage system(s) already exists and a different voltage system is being added, it shall be permissible to mark only the new system voltage. Existing unidentified systems shall not be required to be identified at each termination, connection, and splice point in compliance with 210.5(C)(1)(a) and (b). Labeling shall be required at each voltage system distribution equipment to identify that only one voltage system has been marked for a new system(s). The new system label(s) shall include the words “other unidentified systems exist on the premises.”