Technical information

INDUSTRIAL MACHINERY

NEC Article 409.110

An industrial control panel shall be marked with the following information that is

plainly visible after installation:

1. Manufacturer’s name, trademark, or other descriptive marking by which the

organization responsible for the product can be identified.

2. Supply voltage,phase, frequency,and full-load current.

3. Short-circuit current rating of the industrial control panel based on one of the

following:

a. Short-circuit current rating of a listed and labeled assembly

b. Short-circuit current rating established utilizing an approved method

FPN: UL508A-2001, Supplement SB, is an example of an approved method.

4. If the industrial control panel is intended as service equipment, it shall be

marked to identify it as being suitable for use as service equipment.

5. Electrical wiring diagram or the number of the index to the electrical drawings

showing the electrical wiring diagram.

6. An enclosure type number shall be marked on the industrial control panel

enclosure.

3.1.2 Determining Your Panel Short Circuit Current Rating

Per Section 409.110 of the NEC, there are two permitted ways to determine your

panel short circuit current rating: purchase a previously listed and labeled

assembly or establish the short circuit current rating of the panel using an

approved method. For the latter,the only stated approved method is UL 508A,

Supplement SB.

According to UL508A, Supplement SB4.1, there are three steps to analyze and

mark your panel with a short circuit current rating:

STEP 1Establish the short circuit current ratings of individual power circuit

components.

STEP 2Modify the available short circuit current within a portion of a circuit in a

panel due to the presence of current limiting components.

STEP 3Determine the overall short circuit current rating of the panel.

STEP 1

Establish the short circuit current ratings of individual power circuit components

using one of the following methods:

a) The short circuit current rating marked on the component or on instructions

provided with the component;