Meet UL Requirements and Master SCCR

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SCCR Short Circuit Current Ratings

UL 508A Manufacturer Technical Representative (MTR) Qualification Exam

In a July 2020 bulletin, UL announced a new requirement for each manufacturer covered under the UL 508A standard to have at least one representative successfully complete the UL 508A Manufacturer Technical Representative (MTR) Qualification Examination by February 1, 2021. This is a comprehensive exam on all material covered in UL 508A from component applications and enclosure standards to wiring methods and (short circuit current ratings) SCCR calculation.

Short Circuit Current Ratings

SCCRs establish the level of fault current that a component or piece of equipment can safely withstand. Without knowing the available fault current and SCCR, it is impossible to determine if components or equipment can be safely installed. Supplement SB of UL 508A details the method for determining the SCCR of an industrial control panel. To ensure a safe installation of the equipment, it is important to be able to properly navigate this method.

The overall panel SCCR is determined using the ratings of the internal components of the panel. These ratings include interrupting ratings for overcurrent protective devices and SCCRs of other components. Component SCCRs are always based upon a specific upstream overcurrent protective device type and maximum amp rating. Every component has a standard SCCR, which is its minimum rating required by UL. It may also have a high fault rating or a combination motor controller rating. Taking advantage of these higher ratings will help you achieve a high panel SCCR.

Once you identify the correct ratings for your internal power components, you can determine the overall SCCR of your panel. The method to determine SCCR includes the following steps:

  1. Determine the SCCR of each branch circuit.
  2. Identify the SCCR of each feeder device.
  3. Identify the interrupting ratings of every overcurrent protective device.
  4. The overall panel SCCR is the lowest value from steps 1-3.

Once you have determined your overall panel SCCR, you want to verify that it is greater than the available fault current where the panel will be installed. If it’s not, you will have to swap out lower rated components until the SCCR of the panel exceeds the available fault current.

Master SCCR with the Bussmann MTR Prep Course

Join Bussmann in January for two interactive 1.5-hour virtual training sessions that will review UL 508A Supplement SB definitions and method for determining SCCR. This course will include multiple example problems that will prepare you for the types of questions you can expect on the exam. Attendees will also receive a copy of the training slide deck.

This training is designed for the manufacturer technical representative that will be taking the UL exam, but it would also be helpful for anyone interested in learning more about UL508A and SCCR.

  • Session 1: UL 508A Definitions & Method for Determining SCCR: Tuesday, January 12 @ 1PM ET or Wednesday, January 13 @ 10AM ET
  • Session 2: SCCR Example Problems & Proper Component Application: Wednesday, January 13 @ 1PM ET or Thursday, January 14 @ 10AM ET

This training has passed. Contact us for more information.