Official Luthiers Forum!

Ok, I've finished the shop and now I am onto building benches and jigs making a fair amount of dust. I look over to the electrical outlets mounted onto the cement wall and there's already a coating of dust sitting on them but notice too that they have little holes on the top of the outlet boxes. Obviously some of the dust is getting inside the electrical outlet itself. Do those of you w/ exterior mounted outlets cover these holes or am I worrying over nothing? It seems like a potential fire hazard to me. TIA

That's an interesting question. I've thought about that myself (since I have terrible clean-up habits), but have come to no conclusion. As an electrical engineer, I would think that the dust could potentially create enough of a path for current to arc, and if it does, I suppose the spark could cause combustion. On the other hand, I've seen a LOT of equipment with years of non-shop dust in it, and I've never heard of things (computers, TV's, etc) burning up because dust ignites on the circuitboard or transformer where power comes into the equipment.

One interesting example comes to mind ... Al Carruth's old 386 which before he moved had probably 1/2" of wood dust inside of it! I never understood how the thing kept running!

Same dust problem in my shop but I don't worry about it. The only time you would have arcing in an outlet is if you inserted or removed a plug while the tool was turned on. It's not likely that you would plug a drill in or a sander in with the switch in the on position. As the tool draws current there could be a small arc. I don't ever plug anything in if the tool is in the on position but I'm not saying that it couldn't happen. You could also have arcing if the plug was wired and the terminals are loose.

You could seal up your box holes with silicone caulk. You could also purchase exterior covers with hinged lids or insert those childproof plastic plugs if you think it is a problem. I guess it would give you some peace of mind.

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tim...
http://www.mcknightguitars.com

Pete: I don't think you will have arcing or tracking discharge through the dust unless you have high voltage present. I only have seen tracking in high voltage transformer applications. It's usually only detectable with Ultrasonic or Thermographic test equipment and it's not likely that folks will have these PdM tools availble in the wood shop

There are some ultrasonic sound clips of arcing & tracking at www.uesystems.com if you have any interest in this sort of anomaly. Click on UE Systems at the top left and scroll down to "Sound Demos" and select "Arcing" & Tracking". Click on image at right to hear it.

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tim...
http://www.mcknightguitars.com

Yeah, Tim, I guess I agree at line voltages spontaneous arcing is probably not too likely. Good thought about the loose connections, though. With contacts at the close proximity of a loose connection with running equipment, it sure could arc. Thanks for the web site too.

How well do the overhead dust collection units work like the Delta? Do they take a fair amount of particels out of the air. I just bought one of the sanding tables or mats for most of my sanding. It has a hook up for a 4" hose that I can do with my 2 hp collector. I was just thinking of getting additional overhead hang type

I've had a JDS unit for about a year now, and I have to admit that it really sucks ... a lot of air! I'm surprised at how much dust it traps in the internal bag as well as the washable electrostatic pre-filter. As well as it works though ...

... still, some dust accumulates on surfaces. It's certainly a LOT less than before, though. And, if doing something real messy like routing MDF (heaven forbid!) or resawing, my enclosed dust room of about 8' x 15' goes from "smoky" looking (due to dust) to clear in a matter of 10 minutes or less. Otherwise the dust would hang there for hours, and you'd need a mask just to enter that room.

Just read a sobering article in Fine Woodworking's Tools and Shops issue about a guy's shop which burned to the ground. He theorizes it was a loose connection in the electrical panel which ignited some accumulated sawdust. Makes one want to clean up!

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From Nacogdoches...the oldest town in Texas.

http://www.stephenkinnaird.com

I'd say it's smart keep the dust out of the outlet box. I'm not sure of the electricasl code, but I think to pass an electrical inspection the outlets must have a cover. If the box extends from the wall I think the box should be closed around the four exposed sides. Our resident electrician Bruce Dickey should chime in. Even if the danger is small, if something happened, and the insurance company gets involved they may not cover damages.

I have a Delta overhead filter. They do help alot on the fine dust but don't get it all and the inner fine filters only last so long and are expensive to replace. My main reason for using it is mostly a health thing.

Hey, you could always plumb your vac system into your outlet and main panel boxes

_________________
tim...
http://www.mcknightguitars.com

Static electricity in a dust collection system probably creates a tremendous more amount of voltage, hence the spark that everyone is worried about. KABOOM!

Same thing with Nitro, Blades in the fan are made from aluminum, a metal blade would definitely create a major spark if it contacted. Also there is an explosion proof motor in the proper fan. There are explosion proof switches and light fixtures too. Open flame pilot lights, several ways to get it. KABOOM!

Now, the aforementioned dust in the electric outlet. Duct Tape or caulk would seal the minor holes in the boxes. It's best not to get lots of dust internal to outlets. Or, you could turn a shopvac around and occasionally blow it out, not much to worry about. NO Kaboom!Dickey38380.7764814815

Paul, the boxes have a cover and all for sides are covered. It's just that each of the four sides has two small 1/8" holes drilled in it. It appears they came this way from the manufacturer. This is apparently up to code as the shop passed inspection with these outlet boxes.

Bruce, Thanks for the info. Looks like I'll go the caulk route as I'm not into the clean up thing as much as I should be. Thanks again.

Fine dust in an outlet can conmtain enough moisture to start conducting power to the neutral or groud. I don't know how often that does happen, but I've heard of it happening.

I blow and/or vacuum all my outlets about once a year, and the exposed ones are wrapped in electrical tape to cover up the holes. In an hour, you can have them all sealed up, and a year from now, another hour is all it takes to clean 'em up.

And yes, take the cover off the breaker panel and blow it, too. Then check all the connections, etc.....

Thank you everybody for your thoughts on this. Looks like plugging and occasionally cleaning is the way I'll go.