Working Safely on Energized Equipment – Understanding Restricted Approach, Limited Approach, and Arc Flash Boundaries

When it comes to electrical safety, understanding arc flash hazards and how to mitigate their risk is crucial, but all too often misunderstood. Many workers believe that staying outside the arc flash boundary guarantees safety, but this is a dangerous misconception – one that could lead to severe injuries or worse.

In this excerpt from the 6-Hour NFPA 70E Electrical Safety Training, HeatSpring instructor and arc flash survivor Jason Brozen delves into the complexities of arc flash boundaries, explaining why they’re not “safe zones,” and how to properly set up physical barricades. He’ll discuss the differences between arc flash boundaries, limited approach boundaries, and restricted approach boundaries. Whether you’re an electrician, a safety manager, or anyone working around electrical equipment, this information is an essential foundation for creating a safer electrical work environment. 

Then we get to 130.5(E) and this talks about the arc flash boundary. The arc flash boundary shall be the distance in which you get a second degree burn, right? It says the incident energy equals 1.2 calories per centimeter squared.

I can’t tell you how many times I’ve heard out in the field. Hey, we’ve got our arc flash boundary set up, and as long as you don’t cross that, you’re safe. Well, that’s a fallacy. 

Here’s what it says, that you can get those exact burns if you’re standing at the arc flash barricade. So if your supervisor’s standing there in their Under Armour shirt, short sleeve, and they’re yelling at you because you’re taking too long and you blow it up. It is very possible that they’re going to go to the hospital with their shirt melted to them, second degree burns on their arms, and possible smoke and heat damage to their lungs because they were standing at your barricade. 

You’ve got to keep people away from that barricade. It’s not a safe place. It’s just a place where you’re likely not to die from an arc flash injury. That’s why they limit it to that. If they limited it to no injury at all, arc flash boundaries would be gigantic, and there’s no way they could. You don’t have the space for that typically.

Number two here, the arc flash boundary shall be permitted to be determined  by the tables method. I’m going to go through some of those tables coming up, so you’ll have a basic understanding of that. 

But again, there’s your arc flash boundary. Your arc flash boundary is completely variable. It could be at nine inches. I’ve seen it as high as 65 feet, depending on the piece of equipment. It is completely variable. 

Just to refresh, your restricted approach boundary is fixed at the voltage level you’re working on, and it’s for you as a qualified individual. A limited approach is a fixed level boundary, based on the voltage level.

Then you’ve got your arc flash boundary again, which can be completely variable. Now, here’s one thing I want you to remember, write this down, write this down, write this down.  It is extremely important to get these physical barricades correct.

I’ve already gone over the restricted approach boundary and the limited approach boundary in the arc flash boundary. And again, those are imaginary lines, remember? You need to set up something physical to keep people out of that area. 

If you’re that MCC in this picture right here, 600 volt MCC,  if the limited approach boundary is 42 inches and it is, and the arc flash boundary is at nine inches for this piece of equipment,  where are you going to set up your physical barricade? 

42 inches, right? The thing that you need to remember and write down is you are never, ever, ever, ever going to set your physical barricade less or closer to energized parts than the limited approach boundary. 

So if your arc flash boundary – the imaginary line – is at nine inches and your limited approach is at 42 inches and it would be for this voltage, you will be setting your physical barricade at 42 inches, right?

Very important. The reason this is important is because the same MCC, let’s say your limited approach boundaries at 42 inches. And it is. And your arc flash barricade or your boundary is at 65 inches. And let’s say it is right here, right? You are going to set your physical barricade at your arc flash barricade.

You’re never going to be less than the greater of those two. So the arc flash boundary or the limited approach boundary, which one is bigger? That’s where you set your physical barricade. 

But you’re never going to be less than 42 for that physical barricade. Real important. The reason that’s important is let’s say your limited approach boundary is 42 inches and, and you set your barricade at that, but you do it mistakenly because your arc flash boundary is at 60 feet. 

What happens to the people that are standing around your boundary when you create an arc flash? You’re going to kill them from an arc flash explosion, right? They will be burned to a third degree level. The possibility of death is increased tremendously because they’re not going to be wearing the PPE that you have, right?

You’ve got to get those barricades correct. It’s one of the most misunderstood things in the NFPA 70E. So never less than you’re limited, but always the greater of your arc flash boundary and limited approach boundary is where you’re going to set your barricade.