Metallic enclosures.

Hi to everyone and I wanted to say that I am happy to be a part of this forum. My question stems from an argument I had with an electrical inspector on Friday. Here is the scenario: I was installing a generator, a automatic transfer switch and a feed through panel on the outside of a house (generator was mounted to a concrete slab next to the house). My employer had looked at the job and determined that we were going to have to move the meter base because it feed out of the back directly into the back of the panel in the house. After digging into the situation I found out that this was not the case and the previous electrician had ran service entrance cable out of the back of the meter base, inside the wall to the panel that was about 5 feet away on the inside. So I mounted my feed through panel (to feed the house but also feed a barn that didn't need to be on the generator) then I mounted my transfer switch, I came directly out of the back of my transfer switch to the existing panel inside the house. Now I am a firm believer in making things look nice and look like there was a plan in mounting equipment so I punched my own holes in the feed through panel and the transfer switch to keep the tops of all cabinets even with each other. In the transfer switch there is a back plate that takes up the whole inside so I had to punch a bigger whole in it to keep my conductors protected. the inspector tells me that I must use the eccentric knock outs that are formed in the enclosures because punching my own holes takes away from the structural integrity of the enclosure. He tells me that this is in the code but I can not find it, and though I asked him to show me he didn't and didn't offer an article to look under. If you take out a mounting piece of the enclosure I could see his concern but that is not what occurred, does any one have any in sight in this matter. There were a few other issues I had with this inspector and I really think he just has it out for me (the company I work for) because I proved him wrong on the last inspection of an explosion proof installation. Any in sight would be greatly appreciated, thank you.

Forming or punching your own holes is just fine.

I didn't see anything that would keep me from doing it I mean that's why they make a punch set.

dcspector said:

Forming or punching your own holes is just fine.

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I agree, this is done thousands of times every day. Let the inspector find it in the code book. When he can't, he'll have to pass it.

thomas.a.boardman said:

the inspector tells me that I must use the eccentric knock outs that are formed in the enclosures because punching my own holes takes away from the structural integrity of the enclosure.

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If that was true it would be a real problem for me as we order our panels with no knockouts at all.

Thom, Correct me if I'm wrong. You put a larger KO in the raised mounting back plate so you could KO the box?

Yes I knocked the back plate out larger than the 2 inch hole that knocked out in the actual back of the box, my reason for this was to protect the conductors from getting nicked and shorting out. I am not fond of that action but the back plate takes up the whole inside back of the box. I didn't modify the mounting holes of the back plate or any equipment mounted to the back plate.

I still do not see it as an issue.

thomas.a.boardman said:

Yes I knocked the back plate out larger than the 2 inch hole that knocked out in the actual back of the box, my reason for this was to protect the conductors from getting nicked and shorting out. I am not fond of that action but the back plate takes up the whole inside back of the box. I didn't modify the mounting holes of the back plate or any equipment mounted to the back plate.

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Other then a sealing locknut if the box is outside and edge-guard around the larger KO in the backplate. I once did 3 - 2" KOs in the box with larger KOs in the backplate... I didn't have an issue with the AHJ...

He should provide an article # if it's a violation... I always hate to call the AHJ's supervisor, but sometimes it must be done...

I had an intresting F/A final last week. My inspector said he didn't think I could put my own KO's in F/A back boxes. He called the fire marshall and he said they were concerned about metal shavings on the circuit boards. Now I'm no genius, but 4 screws the boards are out, make KO's, blow the back box out with compressed air and your good to go.

The inspector came back the next morning and sited me on 110.3(B).

I have a nice letter for him when he comes back on Tuesday. The letter is from Honeywell/Silent Knight saying knock em out.

thomas.a.boardman said:

Any in sight would be greatly appreciated, thank you.

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First, please consider breaking long posts into paragraphs. It's just so much easier to read. See if you agree:


Hi to everyone and I wanted to say that I am happy to be a part of this forum. My question stems from an argument I had with an electrical inspector on Friday.

Here is the scenario: I was installing a generator, a automatic transfer switch and a feed through panel on the outside of a house (generator was mounted to a concrete slab next to the house).

My employer had looked at the job and determined that we were going to have to move the meter base because it feed out of the back directly into the back of the panel in the house.

After digging into the situation I found out that this was not the case and the previous electrician had ran service entrance cable out of the back of the meter base, inside the wall to the panel that was about 5 feet away on the inside.

So I mounted my feed through panel (to feed the house but also feed a barn that didn't need to be on the generator) then I mounted my transfer switch, I came directly out of the back of my transfer switch to the existing panel inside the house.

Now I am a firm believer in making things look nice and look like there was a plan in mounting equipment so I punched my own holes in the feed through panel and the transfer switch to keep the tops of all cabinets even with each other.

In the transfer switch there is a back plate that takes up the whole inside so I had to punch a bigger whole in it to keep my conductors protected. the inspector tells me that I must use the eccentric knock outs that are formed in the enclosures because punching my own holes takes away from the structural integrity of the enclosure.

He tells me that this is in the code but I can not find it, and though I asked him to show me he didn't and didn't offer an article to look under. If you take out a mounting piece of the enclosure I could see his concern but that is not what occurred, does any one have any in sight in this matter.

There were a few other issues I had with this inspector and I really think he just has it out for me (the company I work for) because I proved him wrong on the last inspection of an explosion proof installation. Any in sight would be greatly appreciated, thank you.


Second, I agree with you also. I never relent when they're blatantly wrong, whether in fact or in procedure. It sets a bad precedence. Improper inspection failure is as illegal as improper passing.