700.5(E) Emergency System Transfer Equipment. Documentation.

After selecting the applicable combination from the nameplate, the SCCR, based on that combination must then be field marked on the exterior of the transfer switch.
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After selecting the applicable combination from the nameplate, the SCCR, based on that combination must then be field marked on the exterior of the transfer switch.

Transfer equipment is already required to be marked with the short-circuit current rating (SCCR) per UL 1008 which covers transfer equipment. UL 1008 has many options for short-circuit protection of transfer switches and equipment. Transfer switches are usually marked by the manufacturer with several different combinations resulting in multiple options to choose from to ensure proper SCCR values based on the fault current available at the transfer switch.

These marked SCCR values can vary based upon the specific overcurrent protective device type, ampere rating and settings. The transfer switch in the image has a SCCR of 65,000 amps at 480 volts when protected by a Square D Type PJ circuit breaker not larger than 1200 amps. The same transfer has a SCCR of 200,000 amps at 600 volts when protected by a Class L fuse not larger than 1200 amps. When inspecting the specific installation, it can be confusing for an inspector to know which SCCR is valid based on the combination selected by the engineer for the specific project.

To provide clarity, the 2017 NEC® first started requiring the short-circuit current rating of the transfer switch (based on the specific overcurrent protection provided) to be additionally field marked on the equipment.

See the actual NEC® text at NFPA.ORG for the complete code section. Once there, click on the “free access” tab and select the applicable year of NFPA 70 (National Electrical code).

2017-2020 Code Language:

700.5(E) Documentation. The short-circuit current rating of the transfer equipment, based on the specific overcurrent protective device type and settings protecting the transfer equipment, shall be field marked on the exterior of the transfer equipment.

2023 Code Language:

700.5(F) Documentation. The short-circuit current rating of the transfer equipment, based on the specific overcurrent protective device type and settings protecting the transfer equipment, shall be field marked on the exterior of the transfer equipment.

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700.5(E) Emergency System Transfer Equipment. Documentation.

Below is a Real Question from our Electrical Continuing Education Courses for Electrical License Renewal:

Which of the following is true for an emergency system automatic transfer switch (ATS) with a SCCR that varies depending on which type of circuit breaker is protecting it?

A: The AIC of the transfer equipment shall be field marked on the exterior of the transfer equipment.
B: Once the electrician selects the proper circuit breaker to protect the ATS, the SCCR of the ATS, based on the specific breaker type and settings, must be field marked on the exterior of the ATS.
C: The available fault current at the transfer equipment shall be field marked on the exterior of the transfer equipment.
D: The overcurrent device protecting the transfer equipment shall be field marked to identify it as part of the transfer equipment.
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