National Electrical Installation Standards

Standards as High as Your Own

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Tuesday, March 31, 2020

Question:

Good Morning Code questions, I have a working space question about a switchboard that is supplied by a 600/347-volt system. What is the minimum depth of working space required to a grounded surface installed directly in front of the equipment. I appreciate your views and response. Keep up the great work.

 

Mark Summers

A

Answer:

Greetings Mark Summers, thanks for the comments and for the question. Although not a common voltage system in the U.S. there are systems like this in the field. The phase-to-ground voltage is 347 volts. Section 110.26(A) and Table 110.26(A) are applicable and condition 2 must be complied with, at minimum. The NEC requires 3 feet, 6 inches (42 inches) of working space depth in front of the equipment supplied with the voltage mentioned in the question. As a reminder, notes to tables in the NEC are mandatory requirements as compared to Informational Notes throughout the NEC, which are not. Condition 2 at the bottom of the table indicates that an installation with live parts on one side of the working space and grounded parts on the other side of the working space. Concrete, brick, or tile walls shall be considered as grounded.

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