PVC boxes allowed on hot roof?

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Coppersmith said:
Is there any reason I'm not allowed to use a box I have made at a sheet metal shop? Does it have to be listed? Can metal shops make listed boxes or get them listed? I'm asking for next time because the PVC box is already installed.
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How would you certify that it's at least NEMA 3R?
 
Coppersmith said:
I'm running EMT on a flat metal standing seam roof. I need 3R 12x12 and 8x8 junction boxes up there but there doesn't seem to be any metal ones made for this purpose. There's plenty of 3R metal boxes to mount on walls, but I want ones that lay flat with a top that comes off or is hinged.

I've talked to several supply houses who all say everybody uses PVC boxes. Is this true? I'm not allowed to run PVC pipe on the roof because ambient temp will exceed 122 degrees. Seems like a PVC box would be just as likely to melt or deform.
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What is wrong with N4 or 4X. PVC boxes you used are likely 4X.

3R will have drain holes in the bottom and may or may not have a gasket on the cover.

There are N4/N12 cabinets out there that have instructions to drill drain holes to use them for 3R applications.
 
kwired said:
What is wrong with N4 or 4X. PVC boxes you used are likely 4X.

3R will have drain holes in the bottom and may or may not have a gasket on the cover.

There are N4/N12 cabinets out there that have instructions to drill drain holes to use them for 3R applications.
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My only concern was putting PVC on a hot (unpainted metal) roof. I thought it might deform or melt. PVC pipe is prohibited above 122 degrees. Not sure about boxes.


Here’s the kind of temperatures you can expect your roof to reach this summer depending on its surface:

ROOF SURFACEDEGREES FAHRENHEIT ON A SUNNY, 90-DEGREE DAY
Black roof140-190
Aluminum reflective coatedUp to 68 degrees cooler than black roofs
Gravel125-140
Unpainted metal138-145, but feels hotter to the touch than a black roof
Painted Metal (ex: BASF Cool Paint)105-115 or up to 42% cooler than unpainted metal
White102-120
Vegetative90

https://sentryroof.com/news/how-hot-does-your-commercial-roof-really-get-in-the-summer/
 
curt swartz said:
Actually it will. Myers (or and other brand) "Grounding" Hubs have a screw on the nut to connect a wire or lug for bonding.
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Okay, well then I just think 'bonding lockring' is maybe not the correct term. To me that means a lock ring with a screw that tightens to a metal box for the bonding.

Edit: after a bit of googling, I see that 'Grounding Hub' seems to be what Myers calls it, as you mention.
 
electrofelon said:
I have used 3r metal boxes that are designed to mount flat, cover is on top - not sure why you can't find one. Sorry I don't have a part number.
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3R rating only I'm pretty certain will have drainage provisions, some of the enclosures you are thinking of may very have multiple ratings like 3, 4 or 12.
 
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