Field Marking Available Fault Current- NEC 110.24

Equipment

Published on January 3, 2013 by JADE Learning

One question we get on 2011 NEC changes is the requirement to field mark service equipment with the available fault current. A key element to this requirement is posting the date in which the fault current calculation is made. You should be aware of this change, as old labels that predate the 2011 NEC will not be current.

Why is it important to mark service equipment with the available fault current and the date the calculation was made? Changes happen.

The maximum available fault current can be affected by changes made by the utility. The utility may change the transformer supplying a facility. Or, they could make a change upstream at a remote substation. The only way these changes don't have negative consequences is to maintain communication between the facility engineer and the utility.

Marking the maximum available current and the calculation date on the service equipment makes it much easier to confirm the interrupting rating of the equipment.

Do you have questions or comments on this code change? You can learn more about the 2011 NEC changes with electrical continuing education from JADE Learning.