Mounting disconnect over 1 gang plaster ring

[Hotwiredinthevi]

We have a 4x4 box behind drywall on metal studs with a 1 gang plaster ring. It is supposed to feed a disconnect. Initial thought was to mount a blank cover with center ko and flex to the disconnect. Can we just mount the disconnect over the plaster ring and punch a hole in the back of disconnect and pass wires from inside 4x4 to the disconnect? If not what are we violating? Thanks.

 

[Dennis Alwon]

If there is a knockout in the back of the box and there are no splices then I really don't see an issue.

 

[Cow]

I'd rather mount a single gang 4 sq ext box on the 1g mudring with a blank cover and offset nipple into the side of the disconnect.

Putting a disconnect over a 1g ring seems weird to me? You can't do it with lights unless you have a hole in the back of the light as big as the box, so I don't know how a disconnect would be any different?

 

[cowboyjwc]

While I don't think that Cow is way off base if at all, I would probably agree with Dennis, as long as you bush the hole in the back of the disconnect.

 

[acrwc10]

How big are the conductors in the box? I saw this move once and the problem was, they had pulled larger conductors and did not have the correct box size to conduit diameter ratio.

 

[don_resqcapt19]

I would think this would be like the rule for light fixtures in 410.24(B) and the opening in the back of the disconnect would have to allow access to the box itself.

 

[hurk27]

I think this is one of those design issues that the NEC doesn't address very well,because if we want to pull in a requirement for HID lights we might also look at emergency lights and exit signs as they provide no opening to access the junction box behind them, and there are other equipment such as time clocks that would also fall into this problem, other then these items in most cases are not design to be mounted to a box but rather fed from a cable or raceway?

 

[ActionDave]

If there is a knockout in the back of the box and there are no splices then I really don't see an issue.

I agree. Even if there were splices I don't know if it would be a violation.

If you use 410.24 as your guide then you would just have to mount the disconnect to the mud ring and not anchor it to the wall.

 

[Hotwiredinthevi]

After looking at some other postings related to 410.24 in this and other forums it appears that the intent of that section would be to allow surface mounting a luminaire over a box so long as a hole is punched of adequate size and even there it appears as though there is controversy with the A vs B parts of that section. Regardless, in a MH picture on Understanding the NEC on that section you will notice that his graphic shows a hole that is as large as the square to round ring. My intention was to knock out a 1/2" punch on back of disconnect, grommet the hole, and pass wires through (#12's). Notwithstanding the fact that we are trying to apply an entire different section to the question that I had asked, it appears that a 1/2" ko would not be sufficient regardless. Which leads me to the next question. What is the best way to transition from an in the wall application to a surface mount application as is in this case when it's a conduit system? As I stated in the first post, when we roughed in we left a box with the intent of putting a blank cover with a center ko, mounting the disconnect above this box and then FMC to the disconnect. Just wondering if somebody has a better way. Thanks for all the help.

 

[iwire]

I think this is one of those design issues that the NEC doesn't address very well,because if we want to pull in a requirement for HID lights we might also look at emergency lights and exit signs as they provide no opening to access the junction box behind them, and there are other equipment such as time clocks that would also fall into this problem, other then these items in most cases are not design to be mounted to a box but rather fed from a cable or raceway?

The items you mention all mount to the box, not the wall.

 

[infinity]

What is the definition of "any part of the the building"? Would the disconnect switch, once mounted become part of the building?

314.29 Boxes, Conduit Bodies, and Handhole Enclosures to Be Accessible.
Boxes, conduit bodies, and handhole enclosures shall be installed so that the wiring contained in them can be rendered accessible without removing any part of the building or, in underground circuits, without excavating sidewalks, paving, earth, or other substance that is to be used to establish the finished grade.

I would just use one of these with a blank cover and a nipple.

 

[Hotwiredinthevi]

What is the definition of "any part of the the building"? Would the disconnect switch, once mounted become part of the building?



I would just use one of these with a blank cover and a nipple.

Raco 187. Thanks Rob. Probably best solution yet.

 

[davidaengelhart]

I would say depending on the wiring method and if there is a splice in the box. If the wiring method to the flush mounted original box is a cable and the only conductors in the box are going to the disconnect, I see no problem mounting the disconnect over the box, otherwise, accessability is required per 110, and the Raco 187 (as mentioned above) would be necessary.