Why Arc Flash Shouldn’t Be Left to Submittals and Shop Drawings

Division 26 specifications are beginning to change with respect to Power Studies and Arc Flash. But there is still a lot of ground to cover.

More often than not, Electrical Engineers producing Engineering Specifiactions for new construction will specify that Power Studies including Arc Flash Studies are to be performed once the final equipment selection has been made, with results to be submitted for review in the submitted process. To make matters worse, often on the subject of Arc Flash division 26 language ends with general direction to meet NFPA-70 labeling requirement. Sometimes, if your lucky the language also specifies that the requirements in NFPA-70E should also be met. But there several problems with this approach. Here are four of them.

1. Accuracy. For an Arc Flash study to be performed accurately, conductor lengths need to be approximated as close to actual installation as reasonably possible. Often times when equipment manufacturers are looked to for the Arc Flash Studies an assumed standard conductor length is used. This means the calculated incident energy level can be higher or lower than actual making it possible for technicians to use the wrong PPE when working on energized equipment. Not wearing the correct PPE can be deadly. Wearing PPE that isn’t necessary for the task can introduce unnecessary risk. When Arc Flash Studies are performed using accurate information the technicians are provided with the information which provides them with the safest working conditions.

2.Scope. Arc Flash Studies performed during equipment selection and the shop drawing process often fall short of the full scope of coverage prescribed by NFPA-70E. As a result, for the majority of new construction Arc Flash labels are only installed on large equipment such as main switchgear, substations, and main distribution panels. In reality downstream panel boards, disconnects, and other electrical equipment may also require labeling to be compliant with NFPA-70E requirements.

3.Qualitative Information. The requirements in NFPA-70 and NFPA-70E for Arc Flash labeling don’t really match up. In fact, the NFPA-70 lacks a lot compared to 70E, especially with regard to the information required on labels.

4. Poor Coordination. Proper coordination of devices goes beyond just ensuring the closest device to the fault trips first. Through proper coordination studies device settings can be optimized to reduce incident energy available at points in the system which helps to “right-size” PPE requirements for Qualified Persons, further improving safety.

At the end of the day Electrical Engineers are responsible for ensuring the design of safe, reliable systems. This includes ensuring device settings are optimized for performance and safety and ensuring equipment is properly labeled to provide personnel with the necessary information to select the proper PPE.