Fire Hazard Using Vacs as Dust Collectors Please Read

[Keith Outten]

I am making an exception and providing a link to a thread at ShopBot because the topic is a safety issue that may affect a lot of people here. Note that this is not about dust collection catching fire, it is an equipment failure involving an overheated motor.

The thread at ShopBot is called Crispy Bot, those of you who are using a shop vacuum as a dust collector may want to reconsider as they are not designed to run for long periods of time. If you are using your shop vacuum as a dust collector please visit the link below and look closely at the pictures, the result of a fire that was almost catastrophic. In any case the guy lost a very valuable tool and was very lucky that his home and his family were not affected.

Use the right tool for the job and work safely.

http://www.talkshopbot.com/forum/messages/312/29351.html?1207237303

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[JohnT Fitzgerald]

Wow, that is Scary with a capital 'S'. Thanks for the post, I hope it makes people revisit their thoughts about shop safety.

[Ken Fitzgerald]

Oh boy! Howdy!

I'll be purchasing a fire extinguisher for my shop TODAY.

[Randal Stevenson]

I am making an exception and providing a link to a thread at ShopBot because the topic is a safety issue that may affect a lot of people here. Note that this is not about dust collection catching fire, it is an equipment failure involving an overheated motor.



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While I am NOT saying that one shouldn't be aware of this, I am questioning (from reading it), if that has truely been determined as the cause? ANY motor can overheat and catch fire (including a dust collectors), hot carbide could break off the bits, sparks fly and catch a bit on fire, etc.
I think the important thing is NOT to leave your stuff, unattended!

Keith, please keep us updated on this!

[Greg Heppeard]

I have a Fein vac that I've used for dust collection on my ROS only for the past couple of years. I couple of weeks ago, I noticed a funny smell coming from it. After some serious investigation, I found that the motor was arcing and overheating. $175 later, I have a new motor vs >$400 for a new vac. I do have a fire extinguisher in the shop, but hopefully will never have to use it. I've learned over the years to keep your eyes, ears and nose open. If something doesn't look right, sound right, smell right or feel right, something is wrong and I need to find out what it is.

[Pat Germain]

Thanks for the warning and the link, Keith.

I was watching a Wood Whisperer Festool demo recently and Marc mentioned he had a shop vac that kept burning out motors. I think he said he finally determined the vacuum filtration was inadequate which caused the motor to be fouled with wood dust and burn out.

I guess that would be a primary difference between a dust collector and a shop vac. Wouldn't most shop vacs pull dust right through the motor if it isn't properly filtered before getting that far? I recently installed a washable cloth filter on my shop vac. It works a whole lot better than just the paper elements I was running. It no longer spews dust devils when I turn it on.

I have a DC which I used for big machines, but still use my shop vac for handheld power tools. I was under the impression a DC was less than optimal for small power tools and a shop vac was actually better. What do you guys think?

[Ken Fitzgerald]

I'd think part of the problem is in the intended use. Most shop vacs, I'd bet, weren't designed to be used for extended periods of time.....say for a long laser job...thus could overheat...DCs on the other hand are designed for those type of applications. On the other hand, I woudn't want to be pulling "hot" or sparking matter into my DC as that would set up a condition for a smoldering fire in the DC. I don't use DC with my grinder for that reason and my DC has a cast aluminum impeller to reduce that possible sparks should a nail, screw etc be drawn into it.

Interesting what you could and should use for a CNC....?

[Randal Stevenson]

Thanks for the warning and the link, Keith.

I was watching a Wood Whisperer Festool demo recently and Marc mentioned he had a shop vac that kept burning out motors. I think he said he finally determined the vacuum filtration was inadequate which caused the motor to be fouled with wood dust and burn out.

I guess that would be a primary difference between a dust collector and a shop vac. Wouldn't most shop vacs pull dust right through the motor if it isn't properly filtered before getting that far? I recently installed a washable cloth filter on my shop vac. It works a whole lot better than just the paper elements I was running. It no longer spews dust devils when I turn it on.

I have a DC which I used for big machines, but still use my shop vac for handheld power tools. I was under the impression a DC was less than optimal for small power tools and a shop vac was actually better. What do you guys think?

Some saws are setup more for shop vac sized connections, like a BT3100/Craftsmen 21829, but these aren't designed to be running, cutting 3" thick maple, eight hours a day. (different target audience)
Then some (the old Ryobi, the Fein) shop vac's are designed with bypass motors. They get their cooling from external, rather then internally, through the filters. That said, they still aren't continuous motors. But I believe bypass motors are designed to run longer then those that are not!


I'd think part of the problem is in the intended use. Most shop vacs, I'd bet, weren't designed to be used for extended periods of time.....say for a long laser job...thus could overheat...DCs on the other hand are designed for those type of applications. On the other hand, I woudn't want to be pulling "hot" or sparking matter into my DC as that would set up a condition for a smoldering fire in the DC. I don't use DC with my grinder for that reason and my DC has a cast aluminum impeller to reduce that possible sparks should a nail, screw etc be drawn into it.

Interesting what you could and should use for a CNC....?

IMHO, whether you use a cyclone, or Phil Thien's design, for something like this, it should be all metal, and treated as one of those oil rag cans.

[Bruce Benjamin]

Define, "run for long periods of time". I've seen plenty of shop vacs used on job sites, (cleaning up drywall dust, saw dust, etc.) that ran for a lot longer than I've ran mine. I doubt that they were being used outside of the manufacturer's intended parameters. I suppose if you just turned it on when you walked into your shop and shut it off when you finished your project that might be a bit much, maybe. But don't most people just turn it on when they need it? I'd bet that most shop vacs are designed to run for at least 5 or 10 minutes at a time and probably a lot longer than that.

Now if the filter is clogged and the design is that the motor relies on this air movement for cooling then I can see that as being a problem. But that's not really related to just running it for a long period of time.

It's hard to believe that any experienced woodworker would have a shop without at least one fire extinguisher in it. But then again there are also plenty of, "Experts" who operate without blade guards/splitters and eye and ear protection too. It's just about common sense.

Bruce

[Jim Becker]

Thanks for the heads-up, Keith.

Randall brings up a good point, too...the actual design of the vac will also contribute to how long you can safety run it under certain conditions due to the nature of cooling.

[Peter Quinn]

Two things I noticed:

1) The guy is running a CNC using a shop vac as dust collection? What am I missing? Who with half a brain uses a shop vac on a CNC?

2) The OP makes note of "Foam insulation in the rafters catching fire and spreading the fire". Foam insulation has posted on it for good reason a very serious warning about the need to cover it with a minimum 20min fire exposure rated product, like 1/2" sheet rock. Extruded polyurathane foam insulation is a serious accelerant and is intended to be covered. It burns quite hot, the smoke is toxic and it is difficult to extinguish. If you doubt this take a piece out side and light er up!

I would be less inclined to throw out your shop vac and more inclined to either remove or cover ANY exposed foam insulation in your shop or home. A vacuum fire will be mearly annoying compared to a room full of foam on fire.

Under normal conditions the circuit protection on both my PC and craftsman vacs will stop the motor when heat becomes excessive (don't ask how I know this!) Under no conditions do I use either as a chip collector for an industrial woodworking machine or for production volume use on any machine.

The main conclusion I draw from that post is 'That guy wasn't thinking too good'. Glad he wasn't milling magnesium.

[Cliff Rohrabacher]

That had to hurt.