Electrical Equipment Working Clearance

[Designer69]

I have some low voltage control panels (120VAC) and control power transformers that I need to place adjacent to each other indoors in an electrical room.

I understand the front space working clearance requirement of 3’ but I am not clear on the width requirements. From the NEC handbook there is something about a 30” width requirement.

Please see attached image for specific question on what I am looking for.

Any help is appreciated, thanks.

 

[jumper]

Neither of the two bottom areas have a minimum width between the panels.

As shown above, each panels working space can overlap the adjacent one's.

 

[Carultch]

I have some low voltage control panels (120VAC) and control power transformers that I need to place adjacent to each other indoors in an electrical room.

I understand the front space working clearance requirement of 3’ but I am not clear on the width requirements. From the NEC handbook there is something about a 30” width requirement.

Please see attached image for specific question on what I am looking for.

Any help is appreciated, thanks.

You can put two pieces of equipment immediately adjacent to one another with contact between the walls, provided that neither requires clear space for ventilation or cooling by the manufacturer's specs. That's actually the application of a chase nipple, to connect two such enclosures. Be aware that all hinged lids must be able to open 90 degrees, so if the hinge pushes the lid an inch toward the other equipment, you wouldn't be able to butt the two pieces together.

As for the 30 inch width requirement, it can overlap or be shared by equipment smaller than 30 inches in width. And it can be centered, or measured from either side.

When equipment differs in depth, the NEC doesn't specify whether or not you could place a 4" deep load center between two 10" deep disconnects, and share the 30 inch width among all three. The NEC allows a 6" depth difference between raceways that might run above or below, but it doesn't specify whether or not an up-to-6" depth difference is allowed between adjacent equipment sharing a working width. I would see no safety issue.

 

[charlie b]

When equipment differs in depth, the NEC doesn't specify whether or not you could place a 4" deep load center between two 10" deep disconnects, and share the 30 inch width among all three. The NEC allows a 6" depth difference between raceways that might run above or below, but it doesn't specify whether or not an up-to-6" depth difference is allowed between adjacent equipment sharing a working width.

Please allow me to take issue with this concept. Let's talk about the 4" deep panel. The depth of the working clearance begins at the face of that panel. The width must be at least 30 inches. So if you can't take a stick that is 30 inches long and hold it horizontally against the front face of the middle panel, without that stick bumping into both of the 10" deep panels on the left or right, then the 4" deep panel has not met its working clearance requirements. Put simply, you need the two 10" deep panels to be at least 30" away from each other.

 

[gadfly56]

Please allow me to take issue with this concept. Let's talk about the 4" deep panel. The depth of the working clearance begins at the face of that panel. The width must be at least 30 inches. So if you can't take a stick that is 30 inches long and hold it horizontally against the front face of the middle panel, without that stick bumping into both of the 10" deep panels on the left or right, then the 4" deep panel has not met its working clearance requirements. Put simply, you need the two 10" deep panels to be at least 30" away from each other.

So if I visualize this correctly, ignoring hinges for the moment, let's say we have two panels 15" wide by 10" deep and a third panel 15" wide by 4" deep. I mount the 4" deep panel first. 7.5" from the left side I have the right side of a 10" panel and 7.5" from the right side I have the left side of the second 10" panel, so it goes 10" --- 4"--- 10". The edges of the 10" panels are 30" apart and I can slide that 30" stick between them. Yes?

 

[charlie b]

Yes. I believe that would satisfy the clearance requirements for the panel in the middle.

 

[infinity]

Please allow me to take issue with this concept. Let's talk about the 4" deep panel. The depth of the working clearance begins at the face of that panel. The width must be at least 30 inches. So if you can't take a stick that is 30 inches long and hold it horizontally against the front face of the middle panel, without that stick bumping into both of the 10" deep panels on the left or right, then the 4" deep panel has not met its working clearance requirements. Put simply, you need the two 10" deep panels to be at least 30" away from each other.

I agree the 6" permitted encroachment into the space is at the top or the bottom not the side.

 

[Carultch]

I agree the 6" permitted encroachment into the space is at the top or the bottom not the side.

I agree the wording indeed says that not one single inch of depth difference may be allowed for side-by-side equipment.

But I believe in a practical sense, it would be more reasonable to allow slight differences in depth, as long as your 30" stick against the deepest piece of equipment can extend backwards by the required depth. My opinion, and yes I know the wording doesn't allow it.

So for lack of a written compromise for differing depths, you have to build out the smaller equipment on a backing surface to unify the depth when sharing a workspace.

 

[iwire]

So for lack of a written compromise for differing depths, you have to build out the smaller equipment on a backing surface to unify the depth when sharing a workspace.

Yes and it is exactly what I have had to do when mounting say a 18" deep ATS beside a standard 6.75" deep panel tub. I had to make a strut rack to bring the faces of each out flush because I was sharing the work space.

 

[Designer69]

Thank you for the info.

One follow-up question... is there a requirement to how high a control panel (120VAC) can be mounted?

Say I have a 20' ceiling and I am requested to mount it 16' high, where a worker would have to climb a ladder to access it. Is this allowed?

Does it make any sense? No. But I am just curious if that is still allowed by code

 

[jumper]

Thank you for the info.

One follow-up question... is there a requirement to how high a control panel (120VAC) can be mounted?

Say I have a 20' ceiling and I am requested to mount it 16' high, where a worker would have to climb a ladder to access it. Is this allowed?

Does it make any sense? No. But I am just curious if that is still allowed by code

Are there circuit breakers or disconnect switches in this panel?

 

[Designer69]

Are there circuit breakers or disconnect switches in this panel?

nope

 

[jumper]

nope

In that case I do not know of a height limit.