An arc flash label is a tool to be used as a hazard warning and an estimation of the risk should the worker engage in live electrical work. However, electrical work always needs to be justified according to NFPA 70E guidelines regardless of the presence of an arc flash label. Read my article “Justified” for more information on this topic.
The incident energy, PPE level, and arc flash boundary can vary on the same equipment depending on the conditions of the electrical system. For example, a panel may have differing risk levels under normal power than it does under emergency generator power. A proper arc flash risk assessment report will identify the differing levels of incident energy based on the different scenarios within the electrical system. However, the label should contain the worst case of all those scenarios.
Working distances change based on the task being performed, and it’s not possible to include all the different tasks on one label. It is best practice to use a uniform working distance that is the same on all labels within a facility. This avoids confusion and makes the risk assessment more straightforward. In most cases, the working distance will default to 18 inches as this is the average distance from the live circuit parts to the worker’s chest and face assuming the worker is working with his arms outstretched.
1. Incident Energy Analysis Method. This method calculates the incident energy in cal/cm2. This value is reflected on the arc flash label and PPE should be selected based on this value. Table 130.5(G) in NFPA 70E is used in this case.
2. Arc Flash PPE Category Method. This method utilizes tables 130.7(C)(15)(a) and 130.7(C)(15)(b) to identify the task and PPE category. The PPE Category is on the arc flash label, and Table 130.7(C)(15)(c) is then used to select PPE based on this.
Either the incident energy analysis method or the PPE category method can be used, but not both on the same piece of equipment. As a result, any arc flash label should contain just one of these values.
Some facilities prefer to color-code the labels based on risk level. For example: Red = PPE Level 4 (>40 cal/cm2), Yellow = PPE Level 3 (>25 cal/cm2) and so on. I advise against this because it can cause confusion and conflict with ANSI color-coding standards for Danger (Red), Warning (Orange) and Caution (Yellow). In addition, any changes in the NFPA Standard would likely render the color coding out of date.
Some facilities place an arc flash label on each bucket of an MCC and each cubicle of a switchboard. This is overkill and can add more confusion when equipment is already cluttered with too many labels. A worker who sees dozens of labels on the same piece of equipment might get confused as to which label is appropriate for risk assessment or might just simply ignore the warning. The proper procedure for MCC and Switchboards is to place one label on the switchboard.
Two acceptable exceptions are as follows:
1) If the MCC or Switchboard has a main breaker section that is isolated from the remaining sections through a barrier, a separate label may be placed on the main breaker section and another label on the other sections. In this scenario, the main breaker section is protected by an upstream breaker or fuse and will likely have a different incident energy or PPE Category than the remaining sections which are protected by the main breaker in section 1.
2) Large MCCs or Switchboards with multiple sections may have a label on the top of each section, but not on the individual buckets or cubicles.
For equipment such as panelboards, breaker panels, transformers, disconnects, control panels, and ATS units, only one label should be visible on the front of the equipment to avoid clutter and confusion.
Switchgear, switchboards, panelboards, transformers, breaker panels, ATS units, MCCs, control panels, disconnects, and any other equipment that is likely to be serviced are to be part of an arc flash risk assessment and should be labeled.
One label per piece of equipment, visible on front cover