Opinions on romex in exterior facing boxes

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zack1293

New User
Location
Washington
Occupation
Journeyman electrician
I notice moisture or water damage to romex in exterior facing box in general all the time even with a gasket. Especially with devices in lap siding with no trim block for a flat surface. I've always interpreted that to mean inside the box is likely a damp location at minimum and wondered why we aren't required to use uf wire. Shower rated cans could be another example. I know most electricians hate working with uf but I find oxidized copper or devices that have clearly been wet for a long time in fairly new houses
 
zack1293 said:
I've always interpreted that to mean inside the box is likely a damp location at minimum and wondered why we aren't required to use uf wire.
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There is no NEC section that would support that interpretation which is why UF is not required.
 
I think gaskets make things worse, they trap moist air and it condenses and the water can't get out.

You're not changing anything by switching to UF, the conductors and insulation are the same, only the sheathing is different. There are reasons to use UF outside because of the tougher sheathing but if Romex is protected from damage and direct sunlight it survives for decades with no problems.
 
I agree.

Better to drill a weep hole in the WP box and let the ants or mud dobbers in than seal it off with gaskets and let it trap the water inside so that it rusts the bottom screw of your receptacle after the first year and seizes it into place so that it strips off when you go to loosen it and you end up having to change the box out also when you go to change out the shorted receptacle.

If you've been doing this long enough you just know.

Jap>
 
At least the new WR receptacles come with stainless mounting screws now to help minimize that problem.

Wonder what moisture or water damage OP is seeing in the boxes. Tarnished copper is going to be the same regardless of the insulation type. I've seen wet romex and it doesn't seem to deteriorate any quicker than dry romex. The kraft paper inside it may be damp, but it still seems to be intact when it dries out. A previous owner to a house I bought had run NM cable in an under run to a barn and put it inside of poly water pipe to protect it. That pipe was full of water all the time, and that circuit was still working fine on a GFCI after at least 15 years of being there (and I think it was much longer than that as the romex had a green insulated EGC which seemed to be made in the 70's).
 
jap said:
I agree.

Better to drill a weep hole in the WP box and let the ants or mud dobbers in than seal it off with gaskets and let it trap the water inside so that it rusts the bottom screw of your receptacle after the first year and seizes it into place so that it strips off when you go to loosen it and you end up having to change the box out also when you go to change out the shorted receptacle.

If you've been doing this long enough you just know.

Jap>
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I drill the hole, but a also dab just a bit of Kopr-shield on the 6/32 screws. Seems to keep the corrosion away.

Mark
 
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Kopr-shield to me is like Liquid gold.
Every time I pick it up to buy it, I put it back down. :)

Jap>
 
jap said:
Kopr-shield to me is like Liquid gold.
Every time I pick it up to buy it, I put it back down. :)

Jap>
Click to expand...
It gets home before you do.But it’s a great product. I used it on fuse holders on police cars with incandescent lighting that had 20 amp loads, it stopped the fuse holders from melting
 
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