keyholes in load center

[kaiser715]

2nd question for tonight...

Inspection scheduled for tomorrow afternoon, and the last thing left to do is hang my load center in the shop. Metal building, so am hanging the load center off a framework of unistrut. It will mount to 2 horizontal members.

The problem is, the two upper keyhole mounting points on the back of the load center (Square D QO) are in line horizontally with the 3" knockout I am using for incoming power. So, this is a two-part question:

2017 NEC applies in my location.

1) Any restriction on drilling out 2 new mounting holes in the back of the panel for bolting to my unistrut?

2) Will existing keyholes need to be sealed, and how? It is on a dimple in the case, about a 1/2" hole with a 5/16 or so key slot extending from it for about 1/4". You can get your fingertip in and thats about it, or a small mouse. After I (eventually) get my liner panels up, it will be sealed in a wall cavity.

 

[Kevin Essiambre]

I'm not aware of any restrictions on drilling holes into the panel to mount it.

As for filling the holes that are there, it would be a good idea to keep mice and other small rodents out. I would just use silicone or something similar.

Sent from my new phone. Autocorrect may have changed stuff.

 

[kaiser715]

I asked our code inspector today about this.

His response was basically the only thing really addressed by the NEC is that a panel should be 'sturdily mounted' and no openings where somebody could stick something in it, or a rodent, snake, etc could find it's way in.

Said if I drilled mounting holes, he wouldn't know them from a factory supplied hole. Don't ask, don't tell. No issue to do that anyway.

He said I could seal it about any way I wanted to....blob of caulk, tape over it, nut/bolt/washers, etc.

As it ends out, I reconfigured the unistrut a little bit, and was able to use the factory mounting holes.

 

[Kevin Essiambre]

Glad to hear you were able to find a way to make the factory holes work for you.

Sent from my new phone. Autocorrect may have changed stuff.

 

[mark-NJ]

I asked our code inspector today about this.

His response was basically the only thing really addressed by the NEC is that a panel should be 'sturdily mounted' and no openings where somebody could stick something in it, or a rodent, snake, etc could find it's way in.

Said if I drilled mounting holes, he wouldn't know them from a factory supplied hole. Don't ask, don't tell. No issue to do that anyway.

Glad you were able to make it work with the existing holes, but I'd say you have a very 'understanding' AHJ.

Every AHJ I know would knock down drilled holes based on NEC 110.3(B), the real world interpretation of which is "you must follow the manufacturer's instructions", and I assure you Sq.D's instructions say "use the mounting holes" and are silent to drilling your own.

 

[mike93lx]

If the inspector is looking that close and the install is otherwise neat and tidy, he is just looking for an excuse to fail you anyway

 

[mark-NJ]

Here in NJ, that may, indeed, be a piece of the equation....

 

[Bert_]

Glad you were able to make it work with the existing holes, but I'd say you have a very 'understanding' AHJ.

Every AHJ I know would knock down drilled holes based on NEC 110.3(B), the real world interpretation of which is "you must follow the manufacturer's instructions", and I assure you Sq.D's instructions say "use the mounting holes" and are silent to drilling your own.

Dealing with an inspector like that would make me want to either move or get out of the trade.

Most of the inspectors around here have common sense and are concerned with real safety issues. Nobody would care in the least if you drilled your own holes.

 

[driftpin]

While I understand about the "don't tamper with the OEM mounting," (use a listed device in a prescribed manner) if your mounting is similar-to the in-place holes, and the/those unused OEM hole(s) is/are blocked-off to prevent weather, insects/animals from intrusion, if you did get called on it, the chief electrical inspector would probably be the person to speak-to.

Now if your method of mounting was sloppy, or possibly inadequate (only one fastener, where two are required), or otherwise was not done in a workmanlike manner, I could understand the being failed. Just make-sure that isn't the case.

 

[Norcal]

While I understand about the "don't tamper with the OEM mounting," (use a listed device in a prescribed manner) if your mounting is similar-to the in-place holes, and the/those unused OEM hole(s) is/are blocked-off to prevent weather, insects/animals from intrusion, if you did get called on it, the chief electrical inspector would probably be the person to speak-to.

Now if your method of mounting was sloppy, or possibly inadequate (only one fastener, where two are required), or otherwise was not done in a workmanlike manner, I could understand the being failed. Just make-sure that isn't the case.

"Was not done in a workmanlike manner" is not a enforceable part of the code, one persons opinion will be different then another.

 

[alfredeneuman]

"Was not done in a workmanlike manner" is not a enforceable part of the code, one persons opinion will be different then another.

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