What are these "additional overcurrent protective devices"?

[Shackled Designer]

Hi, all.

Reviewing my latest industrial panel design and checking it against, among other standards, NFPA 79 (2012), since the panel supports resistance heating, I was looking at 7.2.11 (Resistance Heating Branch-Circuit Overcurrent Protection), and I noticed 7.2.11.3 which reads:

The additional overcurrent protective devices shall be all of the following: . . .

This is the first of only two occurrences of the words, "additional overcurrent protective devices" in all of NFPA 79, where the second occurs in the immediately-following paragraph, 7.2.11.4:

The main conductors supplying these additional overcurrent protective devices shall be considered branch-circuit conductors.

So my question is this: to what are these OCPDs an addition?

In context, the immediately preceding paragraph requires equipment with multiple heating elements rated above 48A to be designed with the elements subdivided, with each subdivided load protected up to a maximum limit of 60A. Maybe the "additional" OCPDs are these, but, again, what are they in addition to?

Kind regards,
Shack

 

[Jraef]

There are many types of OCPDs, both fuses and circuit breakers, that can be selected to provide very specific protection levels, but are NOT listed for Branch Over Current Protection. So if you use them, they must have a listed branch OCPD ahead of them.