Damp Location - Box requirements?

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  #1  
Old 08-23-07, 09:25 AM
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Damp Location - Box requirements?

I'm in the process of converting what used to be an enclosed porch into an open porch, and am replacing the wiring in the porch ceiling. When I'm done there will be two ceiling-mounted receptacles and a box for an outdoor-rated light fixture. Since the porch is not enclosed, the area under the overhang would qualify as a damp location, so I will need not-in-use weatherproof covers.

The question is- Are there any requirements for the boxes behind those weatherproof covers (e.g. type of box, sealing where the romex enters the box)? They're right under the roof so there's no danger of any direct water, but condensation could conceivably happen within the box since it'll be prone to temperature swings, but probably not enough to cause problems. Since it's on the underside it wouldn't be prone to direct frost or dew.

Also, has anyone seen any slim-profile in-use covers? I wouldn't mind adding a wet location receptacle near the ground but don't want it to be sticking 8 inches out from the masonry wall, people will hit their shins on it...

Thanks!
 
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Old 08-23-07, 09:50 AM
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This is not a wet location. I'm not even sure it would qualify as a damp location. I don't think much in the way of special protection is required. But of course, I can't see it and I don't know how well protected it is and I don't know if you get hurricanes regularly. There's a lot of room for judgment calls here.
 
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Old 08-23-07, 10:00 AM
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Minnesota... definitely no hurricanes or earthquakes :-) We have had plenty of rain though, and the occasional freeway bridge collapse...

My local electrical inspector was kind enough to do a pre-inspection for me before I began any of the work so that I could get a bunch of questions out of the way, he indicated that he would consider the stuff up in the rafters there to be a damp location, and my potential ground box to be a wet location. I think the concern is that you could get blowing snow that would freeze to the underbelly of th eporch and later thaw?

So I certainly agree that the receptacles should have covers, but I would think a standard box would be okay. The ones I intend to use (unless someone on here tells me otherwise) are some sort of tan-colored rigid plastic that looks like fiberglass... Not sure what the material is called but it's not metal and it's much more rigid than the blue plastic boxes that I'm using indoors.

But this brings up another question... NM/Romex cable is okay to use in these rafters, right? Or will I have to totally rethink this and do it in EMT with metal boxes and THWN? Inspector never said I'd have to use conduit, but if it's "damp"...
 
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Old 08-23-07, 10:16 AM
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Are the rafters exposed or is there a ceiling?
 
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Old 08-23-07, 10:28 AM
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For the moment, the rafters are exposed, but that's just temporary during construction (can't cover wiring until after inspection). The old ceiling was painted plywood but it had delaminated on one edge from water damage before I bought the house (roof has since been replaced), water no longer leaks in. New ceiling will most likely be vinyl or aluminum soffit, which typically has tiny holes to make it breathable, but that's as "exposed" as it would ever be; you wouldn't be able to get the wires wet even if you aimed a hose right at the ceiling from underneath.

My guess is that the surface of the outlets is considered "damp", but not the area behind it, hence the need for receptacle covers.
 
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Old 08-23-07, 10:33 AM
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Generally, if the box is mounted in the wall, or in the ceiling (and the wall/ceiling is covered), the boxes can be normal (blue) boxes. The covers must be rated for damp/wet as you're planning. For example, a receptacle mounted on the wall of a house can be run using NM cable into a normal box, with an in-use cover.

If the box is surface mounted, you'll need to use an outdoor weatherproof box.


I've also seen in-use receptacles and covers that are recessed into the box (much like a clock outlet, but with a weatheproof cover). I don't recall the manufacturer - maybe someone here can help.
 
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Old 08-23-07, 12:00 PM
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For the least obtrusive weatherproof receptacle boxes and covers go to the Arlington website. Look for the in and out cover and the inbox.

www.aifittings.com
 
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Old 08-23-07, 01:43 PM
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Thanks, that weatherproof box looks like it might do the trick. The problem there was that my porch is only 5 ft wide in the first place (more like a hallway), and with the depth of the surface-mounted box plus the weatherproof cover, a standard weatherproof "bubble" would be really obtrusive and prone to being bumped/kicked etc to the point that it becomes a safety concern in and of itself.
 
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