My Dust Collection System

Over the years, I've made a few tweaks to my Shop-vac to address some problems and annoyances I've encountered. Today I thought I'd share some tips for people who use a Shop-vac for dust collection.

One supposed advantage of using a Shop-vac as a dust collector is that it's small and light so you can roll it around the shop where you need it the most. At first this sounds like an advantage, but in my experience the vacuum is always in your way, plus you either have to find someplace to plug it in, or use an extension cord which just adds more stuff to trip over.

My solution has been to pick a place for the vacuum to live and keep it there. If you want to use the vacuum on the other side of the shop, buy a hose extension. I have two 8 foot hoses connected by a 2-1/2" PVC coupler. I just drag the hose from machine to machine and coil it in the corner when I want it out of the way.

 

Of course when the vacuum is across the shop, you either have to keep the vacuum on all the time or walk across the shop, weave around machines, and avoid tripping over cords to turn it off after an operation.

To solve this I plugged my Shop-vac into a remote controlled power outlet. If you want to get one cheap, wait for Christmas lights to go on sale -- they'll run anywhere from $10 to $20. You just have to make sure that your load (the Shop-vac) doesn't exceed the rating for the power outlet. In my case my Shop-vac draws 8A (about 1000W) and my power outlet is rated for 1000W max -- not much room to spare, but I haven't had any problems with the setup yet.

Now I just stick the remote in my shirt pocket when I enter the shop and I can turn the vacuum on and off from where ever I'm stationed.

 

Sometimes a Shop-vac is too powerful for the task at hand. If you restrict it's flow by using a reducer, it puts a higher load on the motor and if you're unlucky it'll start whistling loudly. For example when using my orbital sander, my vacuum makes horrible noises and pulls the sander against the surface so hard that it can't collect any dust.

In comes a router speed control to the rescue. You can find them for as little as $20 on sale if you watch carefully. My vacuum switch has been broken for years, so I just wired a plug directly to the motor and use the speed control as the on/off switch. Most times I leave the switch on full, but when the vacuum starts whistling, or I have too much suction I'll switch it over to variable mode and dial down the speed to where I need it.

 

Tools: shop-vac

Tags: dust collection, remote, speed control

Comments

Jeff's picture

Interesting post. I use both a shop vac as well as a Delta dust collector. I tend to use the shop vac on my router table or sander since both are usually across the room from my dust collector. I hate the stiffness of the shop vac hose. I have a smaller hose to connect to my sander which is more flexible and easier to use. Have you worked with different hoses?

Benjamen Johnson's picture

I actually use the 2-1/2" hose with a reducer right at the sander's dust port. I have to wrap some duct tape around it to keep it in place, but I've found the 2-1/2" hose is more flexible than the 1-1/4" hose (at least the ones I have).

I did try buying some cheaper off brand 1-1/4" hose for hooking up to smaller dust ports, but I found that it whistled so bad that it was useless. After that experience I've stayed with the Shop-vac 2-1/2" hoses and a reducer.

rg's picture

Some interesting and useful tips.

"Sometimes a Shop-vac is too powerful for the task at hand. If you restrict it's flow by using a reducer, it puts a higher load on the motor"

However, that is not correct. A vacuum cleaner motor is a centrifugal pump. If you restrict the suction or discharge, the motor has less load on it, not more. It is moving less air, and therefore does less work. If you were to put a current meter on the motor leads, you would see that it actually draws less current when the intake is restricted or blocked.

It's counter-intuitive, and you'd probably be correct in your assumption if we were talking about a positive displacement pump like an air compressor. Think of a vacuum cleaner with a blocked intake like a household fan operating in a chamber which you've sucked all the air out, creating a vacuum -- there would be nothing to resist the fan blades. The increased RPM of the motor is a result of it doing less work, not consuming more power.

That being said, your application with your sander is still good reason to slow down your vacuum. But I think you could achieve the same effect with a simple blastgate valve. Either way, though, you've solved the problem. And for what you say a speed control costs, it probably works out the same and with less hassle.

I love the remote control idea!

Benjamen Johnson's picture

If you were to put a current meter on the motor leads, you would see that it actually draws less current when the intake is restricted or blocked.

That's crazy talk!

Not that I doubted you, but I did hook my Watt meter up to the vacuum and got about 1000-1100W (A little higher than I expected) running free and 800-900W while I was blocking the intake. Just to cheek my sanity I tested my drill press and the number of Watts went up as I loaded the spindle.

I never really thought about it before, I always assumed that the change in pitch was the motor working harder, but your explanation makes sense.

Thanks for the correction.

rg's picture

I'm  not sure if using a watt-meter is an accurate method of checking sanity, but it does prove our theory!  I guess it's one of those counter-intuitive things that doesn't work the way we think they do, when we really start to analyse it.  Sort of like water expanding when it freezes, unlike most other substances.

Interestingly, I just bought a rowing machine that uses a blower wheel on the flywheel to provide resistance.  It has a shroud around the outside with a movable shutter on the side, toward the centre.  When you close the shutter all the way (allowing the blower wheel to suck in less air), it's easier to pull the rower handle.  When you open the shutter to allow more air into the blower wheel assembly, the difference in resistance is pretty significant.  So coincidence provides us with yet another practical application of this phenomenon.