This boundary is only to be crossed by qualified workers and the worker must be protected from unexpected contact. The Restricted Approach Boundary is the distance from an exposed energized electrical conductor or circuit part within which there is an increased likelihood of electric shock due to electrical arc-over combined with inadvertent movement. Let’s go into a little detail on each of these. They can be found in Table 130.4(D)(a) for AC and 130.4(D)(b) for DC circuits. If you have had an arc flash risk assessment performed, these approach boundaries are on your equipment labels. Since these boundaries are for shock, they are determined solely on voltage which makes them very straightforward. Take note that the Restricted Approach Boundary and Limited Approach Boundary are shock boundaries and have nothing to do with arc flash. Limited Approach Boundary (for shock protection only)Īrc Flash Boundary (for arc flash protection only) Restricted Approach Boundary (for shock protection only) Let’s start with an introduction of the three electrical approach boundaries: More importantly, because it is easy to follow, it is more likely to be followed. I’ve said many times that it’s complicated to explain, but it doesn’t have to be complicated to implement.

A panel or task that has a high shock risk might have a low arc flash risk and vice versa. Afterall, the risk for shock and the risk for arc flash are not the same.

Therefore, the protective equipment is different for each event.Īs a result, it would be a mistake to create a blanket system that requires us to wear a full arc flash suit every time we approach electrical equipment. As discussed in earlier articles, shock and arc flash are different events with different injuries and different ways of causing death. The complication arises from the fact that we are trying to protect ourselves from not just one, but two potential hazards-shock and arc flash. In fact, four approach boundaries were taught when I first learned about approach boundaries, until the Prohibited Approach Boundary was deleted in 2015. Why does everything have to be so complicated? When I first introduce the concept, I often get these questions: It’s not that learning approach boundaries is above anyone’s head, but more to do with the fact that there are three different approach boundaries. Approach Boundaries can be one of the most difficult topics for me to explain in my electrical safety classes.

Arc flash boundaries nec 2018