One of the changes that is slowly being instituted by some local AHJ’s is the Short-Circuit Current Rating (SCCR) being applied to Industrial Control Panels. Basically, SCCR is all about safety. It tells us how much short-circuit current a device can withstand without shocking you, exploding, or causing a fire outside of its enclosure. 

It is important to note that the SCCR is different from the Interrupting Rating. The Interrupting Rating is the maximum current we normally see and use with overcurrent protective devices such as circuit breakers and fuses. In addition to the Interrupting Rating, breakers and fuses have SCCR values assigned to them that can be easily overlooked, and the SCCR will vary by the type of breaker and fuse. A 600 amp circuit breaker may have a SCCR of 60,000 amps, 50,000 amps, or 42,000 amps, depending on the type of breaker you purchase. 

According to the more recent editions of the NEC, when you add a new piece of equipment with an Industrial Control Panel, or move an existing piece of equipment, the local AHJ may ask, or determine, what the SCCR is for that device. The local AHJ may require a SCCR of 60,000 amps (60 kAIC) at the device and the Industrial Control Panel may only be rated for 10,000 amps (10 kAIC). This would require you to add a circuit breaker or fused disconnect in the power circuit immediately in front of the equipment in order to achieve the required kAIC of withstand current. What amount of SCCR is your new or relocated equipment susceptible to? This will vary widely within your facility. 

The SCCR’s vary by single phase or three phase, the size of the utility transformer, the location of the equipment within your building, the power cables or bus system, the size of other equipment within your facility, etc. All of these variables need to be coordinated to provide the level of safety that your local AHJ requires before they will let you operate the machinery. 

The local AHJ may require a professional engineer to provide a formal short circuit coordination study to calculate the SCCR’s for your entire facility’s electrical power system. Or they may request a calculation only for the particular Industrial Control Panel. If the later is the case, IAC can help! We have software that will calculate the available fault current and provide you with a copy of the results for your AHJ. 

The National Electric Code is updated every three years, and in 2020 it will change again. Will you be prepared with the correct Short-Circuit Current Rating for the Industrial Control Panel on your equipment when the local Authority Having Jurisdiction comes to call?