Another EC Mag Code FAQ section question

[kwired]

As I mentioned in another thread I was reading the code FAQ's section of 2012 Electrical Contractor magazine and had a couple of Q & A that I want to further discuss. Here is one more question I don't necessarily see eye to eye with the author over the response to a question.

The question was why the requirement for no more than an 1/8" gap around a box?

The key part of the response went like this: "If the gap around the box extends beyond the outside edge of the faceplate, someone could accidently access live parts."

Though I don't disagree with that statement, I don't feel that is the only reason for the requirement. We have had oversized plates for years to solve that problem. You can install oversized plates cover the entire gap and still be in violation of the 1/8 inch gap rule.

Drywall - the gaps are easy to repair - and the drywall finishers usually do repair these gaps. Other wall coverings I have caulked wide gaps and maybe installed an oversized plate for appearance, but the caulk was still necessary to fix the more than 1/8" gap.

Comments?

 

[infinity]

My guess is that it has more to do with the drywall supporting the device and not the plate if the drywall is missing.

 

[kwired]

My guess is that it has more to do with the drywall supporting the device and not the plate if the drywall is missing.

:? Missing drywall means the box is only thing supporting the device doesn't it? What about a combustible finished wall? Device box is supposed to be flush. Gap or no gap, the device is fastened about as secure as it will ever get if the box is flush and device mounting screws are tight.

 

[Smart $]

:? Missing drywall means the box is only thing supporting the device doesn't it?

Seems 314.19 requires "substantial support" by the box itself.

What about a combustible finished wall?

2011 edition 314.21 was changed to only noncombustible surfaces. So a wider than 1/8" gap is not prohibited when surface is of combustible material.

Device box is supposed to be flush.

314.20 permits up to 1/4" set back.

Gap or no gap, the device is fastened about as secure as it will ever get if the box is flush and device mounting screws are tight.

Agree.

 

[infinity]

:? Missing drywall means the box is only thing supporting the device doesn't it? What about a combustible finished wall? Device box is supposed to be flush. Gap or no gap, the device is fastened about as secure as it will ever get if the box is flush and device mounting screws are tight.

Who said anything about a device box? For a mud ring set back 1/4" with a big gap in the drywall the plate will have to keep the device from moving in towards the box. A hard insertion of a plug, especially with some TR receptacles, will break a cheap plastic plate.

 

[kwired]

2011 edition 314.21 was changed to only noncombustible surfaces. So a wider than 1/8" gap is not prohibited when surface is of combustible material.

2008:

Plaster, drywall, or plasterboard surfaces that are broken or incomplete around boxes employing a flush-type cover or faceplate shall be repaired so there will be no gaps or open spaces greater than 3 mm ( in.) at the edge of the box.

2011:

Noncombustible surfaces that are broken or incomplete around boxes employing a flush-type cover or faceplate shall be repaired so there will be no gaps or open spaces greater than 3 mm ( in.) at the edge of the box.

The change only clarifies that it intends all noncombustible surfaces to comply not just drywall or plasterboard type surfaces.

Any idea why they specify no more than 1/8 inch gap for non combustible walls but say nothing about combustible walls?

314.20 permits up to 1/4" set back.

I am aware of this, I guess when I said box must be flush, I was referring to when it is in combustible material.

 

[Smart $]

....

Any idea why they specify no more than 1/8 inch gap for non combustible walls but say nothing about combustible walls?

I am aware of this, I guess when I said box must be flush, I was referring to when it is in combustible material.

I suspect it all has to do with the fire hazard of arcing and arc (and perhaps arc flash) containment.

 

[kwired]

I suspect it all has to do with the fire hazard of arcing and arc (and perhaps arc flash) containment.

But doesn't it seem a little backwards?

If I have a wood finished wall nowhere does it say I must maintain this 1/8 inch or less gap around the box, but I must repair a gap of more than 1/8 inch around a box for a plaster, drywall or other non combustible finished surface

 

[Smart $]

But doesn't it seem a little backwards?

If I have a wood finished wall nowhere does it say I must maintain this 1/8 inch or less gap around the box, but I must repair a gap of more than 1/8 inch around a box for a plaster, drywall or other non combustible finished surface

Yes... but in combustible, the box must be flush or protrude. The cover plate will fit tighter to the box. In non-combustible, if you go to the max 1/4" depth, and have a greater than 1/8" gap, hot arc particles or arc flash can get around the gap, perhaps catching nearby combustibles on fire.

 

[iwire]

I don't necessarily see eye to eye with the author over the response to a question.

How unlike you.

 

[kwired]

Yes... but in combustible, the box must be flush or protrude. The cover plate will fit tighter to the box. In non-combustible, if you go to the max 1/4" depth, and have a greater than 1/8" gap, hot arc particles or arc flash can get around the gap, perhaps catching nearby combustibles on fire.

I can buy into that, but I also think it should only apply if there is set back for the box in non combustible material.