Code Change Summary: Changes were made regarding the short-circuit current marking of industrial control panels.

An “industrial control panel” can be factory made and very elaborate or something as simple as two lighting contactors, field installed in a large junction box. Article 100 defines an Industrial Control Panel as an assembly of two or more components consisting of one of the following:

(1) power circuit components only, such as motor controllers, overload relays, fused disconnect switches, and circuit breakers;

(2) control circuit components only, such as push buttons, pilot lights, selector switches, timers, switches, and control relays;

(3) a combination of power and control circuit components. These components, with associated wiring and terminals, are mounted on, or contained within, an enclosure or mounted on a subpanel.

In the 2014 NEC^®, Section 409.22 required industrial control panels to be installed at a point along the circuit where the available fault current doesn’t exceed the short-circuit current rating (SCCR) of the industrial control panel.

In the 2017 NEC^® the language was clarified and expanded. Now, an industrial control panel shall not be installed where the available “short-circuit current” exceeds its short-circuit current rating. As well, a calculation must be performed to determine how much short-circuit current is available at the control panel. The amount of short-circuit current refers to the amount of current that could be delivered to the industrial control panel under a short-circuit condition that may occur in the control panel.

These rules help to bring everything in compliance with NEC^® 110.10. Knowing the amount of short-circuit current available at the industrial control panel is the first step in selecting the right control panel. For example, if a calculation is performed and it is found that the amount of short-circuit current available at a control panel is 4,999 amps, then installing an industrial control panel with a short-circuit current rating of 5,000 amps is code compliant.

Below is a preview of the NEC^®. 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.