Field Marking Available Fault Current- NEC 110.24

By: JADE Learning | Jan 03, 2013

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.

Available Fault Current

3 thoughts on “Field Marking Available Fault Current- NEC 110.24

  1. I have searched and searched for someone to make these labels,with no sucsess. Where can i buy 2 custom printed labels without having to pay for set up fees or spend a fortune on my own printer?

    1. It is important to understand that NEC section 110.24(A) only requires the field marking “to be of sufficient durability to withstand the environment involved”. This is almost always subject to the Authority having Jurisdiction (AHJ). Many cities allow UV resistant labeling tape such as can be seen in this link:
      Some cities will only allow an engraved label or a raised letter label because they might be concerned with someone painting over the label. Most installers working in these cities obtain these from trophy shops.
      I hope this helps.

Leave a Reply

Your email address will not be published.