PVC Junction Box Covers

tallgirl

tallgirl

Senior Member
Location
Glendale, WI
Occupation
Controls Systems firmware engineer
I was asked a question this morning and I figure I’d give y’all a chance to set me straight.

I was asked if PVC junction box covers can be used on metal 4x4 junction boxes. Other than fire or physical damage reasons, I can’t imagine why a PVC junction box cover can’t be used for boxes containing low voltage controls signals.

One of my colleagues insists there’s a code section which says that if the box is metallic the cover must also be metallic. I can’t find the compliance guy who’d set me straight. I’m at the office and my code box is at home.

What say y’all?
 
A likewise question- would it matter even if we're talking household (<240) voltages?? We regularly use plastic/nylon outlet and switch plates on whatever box is in the wall-- metal, plastic...
 
PaulMmn said:
A likewise question- would it matter even if we're talking household (<240) voltages?? We regularly use plastic/nylon outlet and switch plates on whatever box is in the wall-- metal, plastic...
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It’s not residential. It’s industrial controls. So, 24VAC-ish plus some lower voltage digital stuff.
 
tallgirl said:
I was asked a question this morning and I figure I’d give y’all a chance to set me straight.

I was asked if PVC junction box covers can be used on metal 4x4 junction boxes. Other than fire or physical damage reasons, I can’t imagine why a PVC junction box cover can’t be used for boxes containing low voltage controls signals.

One of my colleagues insists there’s a code section which says that if the box is metallic the cover must also be metallic. I can’t find the compliance guy who’d set me straight. I’m at the office and my code box is at home.

What say y’all?
Click to expand...

A metal 4x4 box is generally what we call a 4 square box and uses a simple 4 square blank cover.
A 4x4x4 PVC Box will generally have 4 cover screws one in each corner that matches the box.

If it's a Hoffman 4x4x4 it will have its own cover that matches.

My question would be, even though you could, unless you've found something in a big box store that just might happen to fit,,,, why would one want to do such a thing in the first place ? :)

Jap>
 
Unused openings are required to be closed by a material similar to the wall of the box. Whether or not that extends to covers is debatable.


110.12(A) Unused Openings. Unused openings, other than those intended for the operation of equipment, those intended for mounting purposes, or those permitted as part of the design for listed equipment, shall be closed to afford protection substantially equivalent to the wall of the equipment. Where metallic plugs or plates are used with nonmetallic enclosures,they shall be recessed at least 6 mm (1∕4 in.) from the outer surface of the enclosure.
 
infinity said:
Unused openings are required to be closed by a material similar to the wall of the box. Whether or not that extends to covers is debatable.


110.12(A) Unused Openings. Unused openings, other than those intended for the operation of equipment, those intended for mounting purposes, or those permitted as part of the design for listed equipment, shall be closed to afford protection substantially equivalent to the wall of the equipment. Where metallic plugs or plates are used with nonmetallic enclosures,they shall be recessed at least 6 mm (1∕4 in.) from the outer surface of the enclosure.
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Thanks. Presumably if they want to get fancy enough with that cover it would be UL-listed.

Also, I do remember the last time we talked about plastic covers and how they had to be made of a material which didn’t support combustion, but I believe that was a UL requirement, not an NEC one.
 
jap said:
A metal 4x4 box is generally what we call a 4 square box and uses a simple 4 square blank cover.
A 4x4x4 PVC Box will generally have 4 cover screws one in each corner that matches the box.

If it's a Hoffman 4x4x4 it will have its own cover that matches.

My question would be, even though you could, unless you've found something in a big box store that just might happen to fit,,,, why would one want to do such a thing in the first place ? :)

Jap>
Click to expand...

It’s going to be a 4 square box you’d buy by the pallet from your favorite supply house.

I work for companies that want to do odd things. They think I’m smart so they ask me questions, some of which I can’t answer on my own!
 
infinity said:
Unused openings are required to be closed by a material similar to the wall of the box. Whether or not that extends to covers is debatable.


110.12(A) Unused Openings. Unused openings, other than those intended for the operation of equipment, those intended for mounting purposes, or those permitted as part of the design for listed equipment, shall be closed to afford protection substantially equivalent to the wall of the equipment. Where metallic plugs or plates are used with nonmetallic enclosures,they shall be recessed at least 6 mm (1∕4 in.) from the outer surface of the enclosure.
Click to expand...

It says the plug/cover material shall provide equivalent protection. It does not say the material has to be equivalent.
 
jap said:
A metal 4x4 box is generally what we call a 4 square box and uses a simple 4 square blank cover.
A 4x4x4 PVC Box will generally have 4 cover screws one in each corner that matches the box.

If it's a Hoffman 4x4x4 it will have its own cover that matches.

My question would be, even though you could, unless you've found something in a big box store that just might happen to fit,,,, why would one want to do such a thing in the first place ? :)

Jap>
Click to expand...
Here is a Carlon plastic 4SQ cover. Cantex and P&S also make them.

1723485230702.png
 
BTW, they also make plastic plaster rings for 4sq boxes.
 
augie47 said:
314.35 seemingly would allow either
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I think you mean 314.25(A), but otherwise agree.

2017 NEC 314.25(A) "Nonmetallic or Metal Covers and Plates. Nonmetallic or metal covers and plates shall be permitted. Where metal covers or plates are used, they shall comply with the grounding requirements of 250.110."

Cheers, Wayne
 
wwhitney said:
I think you mean 314.25(A), but otherwise agree.

2017 NEC 314.25(A) "Nonmetallic or Metal Covers and Plates. Nonmetallic or metal covers and plates shall be permitted. Where metal covers or plates are used, they shall comply with the grounding requirements of 250.110."

Cheers, Wayne
Click to expand...
(Yep, typo)
 
tallgirl said:
I was asked if PVC junction box covers can be used on metal 4x4 junction boxes. Other than fire or physical damage reasons, I can’t imagine why a PVC junction box cover can’t be used
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I agree with the others as long as its not up in a drop cleiing thats a plenum or "other space used for environmental air" 300.22(C)
 
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