Surge-Protective Devices. Short-Circuit Current Rating.

SPD’s are not allowed to be installed where their marked SCCR is exceeded by the available fault current.
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SPD’s are not allowed to be installed where their marked SCCR is exceeded by the available fault current.

Surge protective devices (SPD’s) are often installed to protect panelboards and sensitive circuits from utility line surges. These devices are often shown on the plans for a construction project and the electrician will submit the plans to the electrical parts house when ordering panelboards and switchgear for the project.

It is critical that the Available Fault Current (AFC) is made known before the equipment is ordered to ensure that the SPD has the correct short-circuit current rating (SCCR).

NEC 242.10 requires that the SPD shall not be installed at a location in the circuit where the AFC exceeds the SCCR of the SPD. This requirement is not specific to SPD’s installed in service equipment alone. SPD’s are often installed downstream of the service and the only way to comply with NEC® 285.10 is to determine the amount of AFC where the SPD will be installed.

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 Code Language:

285.7 Short-Circuit Current Rating. The SPD shall be marked with a short-circuit current rating and shall not be installed at a point on the system where the available fault current is in excess of that rating. This marking requirement shall not apply to receptacles.

2020 Code Language:

N 242.10 Short-Circuit Current Rating. The SPD shall be marked with a short-circuit current rating and shall not be installed at a point on the system where the available fault current is in excess of that rating. This marking requirement shall not apply to receptacles.

2023 Code Language:

242.8 Short-Circuit Current Rating. The SPD shall be marked with a short-circuit current rating and shall not be installed at a point on the system where the available fault current is in excess of that rating. This marking requirement shall not apply to receptacles.

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Surge-Protective Devices. Short-Circuit Current Rating.

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

Which of the following is true?

A: Receptacle type SPD’s must be marked with their SCCR.
B: It would be code compliant to install a SPD with a marked SCCR of 25kA in a switchboard where the AFC was 25,000 amps.
C: It would be a code violation to install a SPD with a marked SCCR of 25kA in a switchgear section where the AFC was 25,000 amps.
D: SPD’s must be marked with an AIC rating.
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