Does screwing onto the front cover of a panel board/ control panel prevent UL listing?

[oscarwong]

Was told by a contractor that he cannot put screws on the front of a panel board? Is this correct? Any Code citations would be greatly appreciated, Thank you! Picture as a reference, those screws holding the plate, is that allowed?

 

[Dennis Alwon]

I am not sure what screws you are talking about. Do you mean the screws that hold this label?

 

[hbiss]

I would think those screws (or rivets) were put there by the manufacturer, no?

-Hal

 

[infinity]

We use rivets or screws to attach phenolic labels all of the time.

 

[jap]

Was told by a contractor that he cannot put screws on the front of a panel board? Is this correct? Any Code citations would be greatly appreciated, Thank you! Picture as a reference, those screws holding the plate, is that allowed?

I would tend to side with the contractor.

If it's a label that should come from the factory it should either be a label of the stick on type, or, if needed to be bolted or screwed on they should have provided the holes at the factory in a place where they want the label to be in my opinion.

JAP>

 

[roger]

We use rivets or screws to attach phenolic labels all of the time.

Same here, many, many, many times and more. If they didn't want us drilling holes for rivets or screws they should provide them from the factory so we can label them.

 

[roger]

or, if needed to be bolted or screwed on they should have provided the holes at the factory in a place where they want the label to be in my opinion.

JAP>

I share that opinion if it is indeed a problem.

 

[infinity]

Same here, many, many, many times and more. If they didn't want us drilling holes for rivets or screws they should provide them from the factory so we can label them.

Yeah this seems like a no brainer. How would drill two small holes in the cover change anything? I've seen many panelboard covers with field installed hasps and locks too.

 

[zbang]

I think your contractor needs to bring the citations why it wouldn't be allowed. (I don't see a problem with small holes to mount a label plate. I'd also ask them how the front is different from the sides or back.)

 

[kwired]

I would tend to side with the contractor.

If it's a label that should come from the factory it should either be a label of the stick on type, or, if needed to be bolted or screwed on they should have provided the holes at the factory in a place where they want the label to be in my opinion.

JAP>

In the example pictured that plate, label, whatever you want to call it was installed at the factory, it is listed and approved as is.

If you want to field install some sort of label that needs to be screwed/riveted on then how that might impact the ingress rating of the enclosure should be at least a consideration. An indoor only NEMA 1 enclosure, you can probably do quite a few different things.

If it is an explosion proof enclosure, probably best not to try anything that puts a hole in the enclosure period.

 

[Eddie702]

When I saw the post, I was thinking about the panel covers that mount with the 6 or so dogs that grip the lip of the cabinet. When there 40 years old and falling apart I have no problem drilling and tapping a few holes in them for 10-32 screws. Don't know what you guys do.

 

[paulengr]

Was told by a contractor that he cannot put screws on the front of a panel board? Is this correct? Any Code citations would be greatly appreciated, Thank you! Picture as a reference, those screws holding the plate, is that allowed?

The UL listing for a panelboard includes the rails. You can actually buy bus bars that are Listed as a panelboard. So not an issue there.

The enclosures are typically “NEC enclosures” which are not Listed. Even when they are as long as whatever you use is the same rating it’s fine. So for instance installing a NEMA 12 push button into a NEMA 12 (oil tight) panel would be accepted but not running NMB into it with a 2 screw cord grip which leaves an opening for dust.

MANY meters, displays, controls, filters, fans, coolers, and other devices which have the same rating system as enclosures mount with screws in holes. It would be ridiculous if you had to mount all operator controls and displays on the sides of an enclosure.

I can understand if it’s not flat, cast, or otherwise makes it difficult or impossible to mount something but otherwise that would completely compromise effectively every single industrial control panel,

I’d treat that like any inane inspector statement…show me the Code!

 

[Fred B]

Was told by a contractor that he cannot put screws on the front of a panel board? Is this correct? Any Code citations would be greatly appreciated, Thank you! Picture as a reference, those screws holding the plate, is that allowed?

Your picture is of a switch enclosure. Putting a machine screw into an enclosure cover not likely an issue but to put a screw into a panelboard that is not part of the listed product design might very well be a violation. The enclosure of a panelboard is not necessarily listed item and code does allow for alteration that doesn't compromise the integrity of the enclosure for stated purpose, ie in a NEMA 3 enclosure creating an opening that would compromise the water intrusion integrity in a wet area.

Additionally what sort of screw being referred to? The screws I've seen some guys try to use like self tappers, sheet metal or wood screws can and have caused damage to conductors by incidental contact of the sharp edge or points.

 

[jaggedben]

I think putting screws through the front of a listed piece of equipment is arguably a violation. 110.3(B). You are modifying the equipment other than according to instructions. Surely small metal screws don't matter on the deadfront or cover of a switch or panelboard, but if you say that's okay then where do you draw the line?

All the signs and placards I've ever attached were adhesive backed.

 

[kwired]

I think putting screws through the front of a listed piece of equipment is arguably a violation. 110.3(B). You are modifying the equipment other than according to instructions. Surely small metal screws don't matter on the deadfront or cover of a switch or panelboard, but if you say that's okay then where do you draw the line?

All the signs and placards I've ever attached were adhesive backed.

But you can make holes for raceways, push buttons, selector switches, indicator lamps, panel meters, etc. and that it fine?

The listing requirement is for manufacturers to comply with when they make the item. Now if it would create a major problem to make modifications that would likely be in the listed instructions, like my example earlier of drilling a hole in an explosion proof enclosure, that typically is a big no, no you generally will compromise the explosion proof characteristics of the enclosure if you do so. Not even a mounting hole or a hole for a grounding screw in that situation.

 

[paulengr]

But you can make holes for raceways, push buttons, selector switches, indicator lamps, panel meters, etc. and that it fine?

The listing requirement is for manufacturers to comply with when they make the item. Now if it would create a major problem to make modifications that would likely be in the listed instructions, like my example earlier of drilling a hole in an explosion proof enclosure, that typically is a big no, no you generally will compromise the explosion proof characteristics of the enclosure if you do so. Not even a mounting hole or a hole for a grounding screw in that situation.

If that were the case you could not attach a conduit (with a seal) to an XP enclosure.

 

[jaggedben]

But you can make holes for raceways, push buttons, selector switches, indicator lamps, panel meters, etc. and that it fine?

Um, no, it's not fine at all. Not unless the instructions make clear it's designed for that.

My statement was about listed equipment.

(Also generally no sane person makes holes for raceways in the front of equipment.)

The listing requirement is for manufacturers to comply with when they make the item.

And therefore the installer cannot modify the equipment without instructions because then it might no longer comply.
The code enforces this with 110.3(B).

 

[paulengr]

Your picture is of a switch enclosure. Putting a machine screw into an enclosure cover not likely an issue but to put a screw into a panelboard that is not part of the listed product design might very well be a violation. The enclosure of a panelboard is not necessarily listed item and code does allow for alteration that doesn't compromise the integrity of the enclosure for stated purpose, ie in a NEMA 3 enclosure creating an opening that would compromise the water intrusion integrity in a wet area.

Additionally what sort of screw being referred to? The screws I've seen some guys try to use like self tappers, sheet metal or wood screws can and have caused damage to conductors by incidental contact of the sharp edge or points.

Even manufacturer supplied screws are subject to this if the wiring is not secured and routed properly. UL/NEC do not define modification nor do they define neat and workman like manner. Those are all calls by the AHJ. You can also pinch loose wiring while closing a door regardless of how screws are used.

AHJ has some responsibility here if the workman can’t manage to do things properly. That being said if you look at a panelboard most are designed to accommodate field wiring. However the same thing can’t be said for a lot of switchgear control panels, MCC buckets, and most industrial control panels. The manufacturers simply fail to provide adequate space for field wiring. Many fail to meet even wire bending space rules or only allow for side and not top entry (which has larger requirements) or provide nothing to work with for mounting. There is NO safe place to screw anything into an MCC.

 

[electrofelon]

Um, no, it's not fine at all. Not unless the instructions make clear it's designed for that.

My statement was about listed equipment.

(Also generally no sane person makes holes for raceways in the front of equipment.)


And therefore the installer cannot modify the equipment without instructions because then it might no longer comply.
The code enforces this with 110.3(B).

Not sure I've ever seen instructions giving me permission to punch holes for conduit entries . I don't believe panel board cabinets have to be listed, but I believe they usually are.

 

[kwired]

If that were the case you could not attach a conduit (with a seal) to an XP enclosure.

generally with XP enclosures you can only enter with raceways into hubs that are integral to the enclosure. There is no drilling to make another entry because AFAIK there is no "myers hubs" designed for this situation. You might be able to drill to add entries, but it will never be suitable for use in XP application again