When running electricity for industrial applications, safety and functionality concerns are paramount. You need to arrange things in a way that is easy to use, provides power as needed, and doesn’t create undue risks.
Fortunately, there are building codes that spell out exactly what you need to know to properly space out your electrical enclosures. While the rules are long and complicated, you can simplify your understanding by breaking everything down into two simple concepts: access and spacing. How do you arrange things to provide adequate access for technicians? At the same time, how do you space enclosures to minimize dangers? You’ll see the formal answers to both questions below.
The first concept to consider is spacing. But, even breaking things down like this, there are multiple elements at play. So, let’s start with the codes.
The National Electric Code (NEC) and National Fire Protection Association (NFPA) set the rules for spacing in industrial electrical enclosures. The rules are all about safety, and there are basically two ideas. First, people need to be able to access the boxes in order to respond to an emergency. Second, the boxes need to be spaced to reduce the risk of fire.
In terms of access, there’s a simple rule (that is codified in both standards) to get you started. Boxes need to be spaced so that every single panel can be accessed by a technician performing their duties simultaneously, with the doors open.
Imagine an electrical room with three panels. Those panels should be spaced so that you can have all three doors open at the same time, and nothing is blocked from any of the panels. At the same time, a technician needs to be able to physically fit in the room to access all of the panels at the same time. Lastly, they need to be able to pass by each other, so you need the room spacing to be at least two people wide.
It’s easy to understand this rule when you think about it. Imagine that a fire breaks out so that technicians need to kill power to every system in order to reduce the danger. Three people might run into that electrical room, and they need to be able to shuffle past each other to go through each box, all at the same time.
If you follow this rule with your design, you’re off to a good start.
The other big consideration is fire danger, and that is largely determined by currents and voltages running through the enclosures. These rules apply to non-accessible enclosures and panel enclosures alike.
First, consider the voltage. Enclosures that service higher voltages need more space. If the combined voltage running through the enclosure is less than 600V, then each box needs a minimum of 1 meter of space between it and any other box. For some designs, you might need to push that closer to 1.3 meters in order to give supplying cables enough space, but that’s not an enclosure regulation.
If the enclosure services more than 600V, then the spacing increases according to the total voltage. At the highest end, voltages above 75kV require at least 4 meters of space on all sides. Meanwhile, 600V-boxes only need 1 meter each. The space scales linearly, so you can roughly add a meter of space for every 20kV.
The last rule has to do with general fire danger. Any electrical room that services more than 1200 amps needs to have two exits.
That’s the list of rules, and following them, it’s easy to understand how to space your enclosures for the sake of safety and reasonable access.