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I have a 1-gang box that I'm installing a switch in, for my wood shop. I need to make it dust-resistant, if not absolutely dustproof. I can't use a waterproof box because I don't think they're made for the depth I need (3.5") to fit the switch. Do they sell covers for the screw holes of j boxes, like they sell knockout covers? If so, what are these things called? If not, what are some other possible approaches?

user278411
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  • Does this absolutely need to be an ordinary light switch, or can it be a "safety switch" type of device? – ThreePhaseEel Oct 30 '20 at 00:00
  • Also, what wiring method is used for the wires coming into this box, and is the existing box surface-mounted or flush-mounted? – ThreePhaseEel Oct 30 '20 at 00:10
  • The switch is not a light switch. It is a safety paddle switch. The cord entry points are not a problem. I'm using waterproof cable glands. The only problem I have is sealing the screw holes. – user278411 Oct 30 '20 at 01:02
  • Can you link the make and model of the switch then please? – ThreePhaseEel Oct 30 '20 at 01:19
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    Can you provide a picture of the switch? – MonkeyZeus Oct 30 '20 at 12:48
  • It might be worth addressing the dust problem from a different perspective. What is generating all this (presumably wood saw) dust? A miter saw, I'm guessing? A table saw? Typically saws that produce a lot dust have a dust-outlet that can be hooked up to a bag. A better solution is to attach a shop vac to the sawdust outlet, turn on the shop vac, so that there's positive pressure pulling sawdust into the shop vac instead of letting dust fly out and cover everything in the vicinity. – TylerH Oct 30 '20 at 15:21

3 Answers3

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Use a weatherproof box and a weatherproof extension ring (or rings if you need a lot of depth) if you cannot find a weatherproof box to suit.

Or, just seal up the box with duct seal (non-hardening electrical putty for sealing up conduits.)

Unless you use a weatherproof switch enclosure (which may not be compatible with whatever absurdly deep switch you have chosen if it's not like a normal toggle switch at the mounting end) the switch itself will be an entry for dust into exactly the places you most don't want it.

Depending on the nature/purpose of the switch, enclosing the entire switch behind a gasketed door might be appropriate - but not if it's something that requires immediate access, like an emergency stop (though most of those are dust-resistant and/or waterproof, or available that way, anyhow.)

Addressing dust collection/control is another approach. It's not good to breathe that stuff, so getting it out of the air ASAP is good for you AND your electrical items.

Ecnerwal
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Look for switch/outlet insulators, like this one (Note: just the first one I found in a search, no recommendation of vendor or retailer implied.)

It's a thin foam gasket designed to go under the cover plate to keep cold air from coming in through the box, but should do a reasonably good job of keeping much larger dust particles from getting into the box, too.

Also, they're dirt cheap. (I found one source for receptacle gaskets for 10¢ each.)

FreeMan
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In the US, NEMA (the National Electrical Manufacturers Association) is the standards body which establishes standards for this type of thing.

It looks like you want a NEMA type 5 box: Wikipedia Article on NEMA Enclosure Types

Flydog57
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  • The OP's issue is that NEMA enclosures are a completely separate thing from standard wall boxes (and not generically compatible with wallbox devices, *of course*); "safety switches" are made in NEMA 4X or 12/3R combo enclosures for industrial work, but are rather different beasts than a wall switch – ThreePhaseEel Oct 30 '20 at 00:01
  • I believe that a NEMA type 5 box isn't much more than a normal box with dust-proof foam gaskets. It's when you get into types 7, 8, and 9 (for example, dust-proof enough to use in an explosive environment like a flour mill) that things get complicated. Then again, I haven't cared about this in about 30 years so I may be completely off base. – Flydog57 Oct 30 '20 at 00:07
  • Yeah -- I believe a normal wallbox + coverplate is roughly equivalent to NEMA 1, but nobody ever bothers assigning NEMA ratings to those, either :P – ThreePhaseEel Oct 30 '20 at 00:09
  • I was thinking something like this (though it doesn't seem to have a NEMA rating): https://www.amazon.com/Hubbell-5123-0-Weatherproof-Vertical-Decorator/dp/B07F1C6V8J/ref=pd_bxgy_img_2/130-6607640-9673650. I use Sealproof brand covers for my outside plugs/switches. I suspect "weatherproof" will likely be dustproof enough for this application (again, not a flour mill) – Flydog57 Oct 30 '20 at 00:18
  • @J... -- well, it'd be an enclosed safety switch in something like a NEMA 12 enclosure (since switches of that type aren't made in NEMA 5) – ThreePhaseEel Oct 31 '20 at 03:09
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    @ThreePhaseEel Sorry, I misread your original comment. In any case, I think OP should really consider a proper NEMA or IP rated switch. It's a different beast, yes, but it's the right tool for the job in a dusty woodworking shop. – J... Oct 31 '20 at 11:12