Code Change Summary: The voltage levels and measurements in Table 110.26(A)(1) have changed.

NEC Table 110.26(A)(1) provides the minimum required work space depth for electrical equipment rated 0-1000 volts (to ground) that is likely to be examined or worked on while energized.

For quite some time, this table stopped at 600 volts and the work space depth for anything higher than that was determined from Table 110.31 in Part III of Article 110.

In the 2017 NEC^®, new dimensions are given for work space depth when the voltage to ground is between 601 volts and 1000 volts. Conditions 1, 2 and 3 under the table remain unchanged are critical in determining proper working space (see image).

Work space depth is measured from the exposed live parts or from the enclosure or opening if the live parts are enclosed (such as a panelboard inside a cabinet).

See the illustration for a preview of the revised Table 110.26(A)(1). 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.