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I have conflicting answers from vendors whether venting a dust collector directly outside will harm the DC motor. Make up air is not a problem. I can discharge into a field, and nearest neighbor is 1/4 mile away. I would like to avoid the cost and cleaning considerations of filter bags/cannisters.

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    What's the premise for thinking it would damage the motor? – Steven Dec 16 '15 at 0:57
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    What Steven says. You need to clarify because nothing you've described seems related to things that can damage motors. I can take some guesses at what filters and such you are referring to, although I am unsure of the significance of the distance to your nearest neighbor, but perhaps a picture and some clarification of your specific concerns would help. You mention outside a lot, are you asking about weatherproofing it? – Jason C Dec 16 '15 at 5:09
  • Make sure there's no way weather could block it or push moisture back down into the blower. And depending on the woods you're working with, the dust may be somewhat toxic. But other than that... – keshlam Dec 16 '15 at 7:56
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    You're what's going to be damaged, not the motor. For the motor, it's actually favourable (less pressure to work against). Though the blower's impeller will have a little more wear with chips and dust scratching over it (but I guess that is not that big deal). What's important, however, is that venting outside directly will put the fine particule matter right next to where you are breathing. You will either suck it in again through the air inlet, or have it ninja through an open window, or breathe it in when you go outside. Don't do that. A filter really is not that expensive. – Damon Dec 16 '15 at 9:13
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    @keshlam: Pollen is (apart from allergy) pretty harmless, greater 10µm -- gets stuck in your upper respiratory tract and is coughed out. Woodworking shavings and dust can be anywhere from 3 centimeters down to 0.5µm. Which is "virus size", not "pollen size". And, which is just the stuff that a) stays in the air for several weeks, b) is invisible, so you can't really be sure whether it's there or not, and c) goes into your alveoles. – Damon Dec 16 '15 at 17:55
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I think it depends on the machine. Many dust collector motors are designed to run against a certain amount of resistance provided by the actual dust collecting parts.

My system wouldn't work the way you intend because of the design, however, my dad's dust collector is basically a large fan mounted on the wall. His is designed to do what you appear to want, however, he couldn't just let it vent straight out with the 8" pipe it was designed for. He ended up having to constrict it down to a 4" pipe so there was enough resistance he wouldn't burn out the motor. The other option was to give it about 20' of pipe to push the dust through, which wasn't convenient.

So the answer is both yes and no. Yes if you just vent it straight out you could severely damage your motor after some use. However, there are ways to fix the problem. I would recommend getting the help of an electrician to figure out the load balance needed but it can be done without damaging your motor.

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  • I can't speak to the motors in dust collection systems, but I know for a fact the blowers in furnaces require a certain amount of resistance or they will burn out. Given that, I strongly suspect @bowlturner is right about this. – Katie Kilian Dec 16 '15 at 16:19
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For most fans, if you restrict the exhaust, the fan will turn slower as the motor tries to push the air it sucked in against the restriction.

If you have an unrestricted open exhaust and for some reason the inlet gets clogged, likely occurrence for a dust collector, the impeller will spin up to the unloaded speed (almost) of the motor. As there is less air for the blower to process, there is also less air friction, it is basically running in the partial vacuum it created.

If the impeller or motor is not rated for operating that speed, damage could occur.

I think DC motors without speed controllers have that problem most often.

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