Variable Speed Shop Vac

I read somewhere that a person found their Shop Vac too loud and used a variable speed controller to slow it down.

Yes my Shop Vac is much louder then the router and I thought I would try this. I went to Amazon and ordered a variable speed controller for a router. It said it worked on exhaust fans and other brush type motors. They are very common unit and only about $30 so I thought I would try it.

First impression was it works great. Slowing it down to about 80% seem to have no negative effect on removing the chips and the sound was now only 1/2. Awesome.

However on the down side. after 20 minutes, the metal heat sink on the back of the hand held variable speed controller box was very hot. too hot to hold in my hand for any length of time.

It is rated for “15 amps” and the Shop Vac draws around 6 ish amp. I guess for a router there is a duty cycle. but they did say fans, And like all of these Amazon things, there was very little of a manual so it never mentioned a duty cycle. nor UL listed or CSA approved or … :slight_smile:

I did find it interesting that turning down the speed just a bit had a great improvement in reducing noise.

I am looking for some thoughts as to if anyone has done this long term. Did the Shop Vac burn up :slight_smile: … Is this just a cheap control unit… I should not run my Shop Vac for long periods of time … I should get a real dust collector .:slight_smile:

The problem w/ the brushed motors and reducing the speed is that they are usually designed to cool based on airflow and reducing the speed reduces the airflow, so they overheat.

Back when I was first using my machine, I used a pair of household vacuums for dust collection — when one would overheat and go into thermal shutdown, I’d swap in the other — managed some long cuts thus, but a dedicated unit which is designed for long run-times is far more convenient and probably safer.

Above all, make sure your unit has a HEPA rating suited to the material you are cutting, or that you add a suitable HEPA filter.


I haven’t tried it. But I have put some kind of muffler on the output, even a section of hose will help a little. Some reduction in vacuum.

Anecdotally, I haven’t burnt up a Shopvac, at least the Rigid versions I typically buy. I’ve had them plugged into holes cut into closed cell foam for days on end with very very little air flow. On large cavity’s not suited for a vacuum pump, I was able to dry considerable quantities of saturated closed cell foam.

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I use a Miele vacuum paired with a cyclone separator. Miele vacuums have more suction that many shop vacs and have a secondary fan on their exhaust which shifts the noise up into the ultra sonic range making them considerably quieter. Mine also have a speed control. I have run hour long jobs and the Miele hasn’t gotten particularly hotter than it does after five minutes. They are expensive new though. I recommend finding one on eBay.


I built a 3/4” plywood box for mine. On casters. Lined it with1” of styrofoam sheet. Found a cheap remote push button control outlet on Amazon.

Cut a 3 inch hole in the back for exhaust. Put an elbow in that hole to enable hose attachment for directing exhaust outside the garage when lasering with the garage door shut.

Plopped a dust deputy on top. Acquired about 30 feet of vacuum hose, ran along ceiling across L brackets for easy access, parked the vac-in-a-box in the far corner of the garage, never looked back. 3-4 years operating 2-6 hours per day, smaller Rigid vac. Oh, makes a great “central vac” too, disconnect from hose to Shapeoko, can vacuum most of the garage. Just don’t forget to empty the Dust Deputy bucket.

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I had a Porter Cable 690 router which is a single speed. I got a router speed controller and installed. That lasted about a year and my 690 was burned up. I dismantled it and the motor windings were burnt to a crisp.

I got a variable speed router. I believe the speed controller burnt up my great 690 router.

I cant; magine a router motor and a shop vac are much different.


I shop son Amazon ( not as much as the wife)
I like to see where the purchase is being shipped from as the stuff from China is not upto USA or EU standards
Variable speed items tend to be just a potentiometer to reduce the voltage rather than a dedicated variable transformer that can dissipate the heat better
Just my opinion

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Super interesting- can you send the model number

Wow thanks for the awesome feedback and great ideas.

My concern is the long term effect to my Shop Vac. I assume the controller is a triac that kind of chops up the AC wave form. I believe it produces a not so smooth wave form with sharp edges. I don’t know what that does long term to a motor. Works fine for light bulbs thought :slight_smile:

I might have to look at muffling the sound :slight_smile:

Chopping wave form or amplitude is normally for rf or sound to increase the rms, that why adverts on tv sound louder than the tc program you were watching

I bought a Record Power DX4000 vacuum that has two motors which can be run individually or concurrently. For anybody in the UK, it’s almost as good as two household vacuums :wink:

Perhaps there’s something similar in the US?

It is a Miele Ariel.

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I have gotten two variable speed controllers. Both were garbage. A friend let me use one that is a lot pricey. It worked well. Ended up deciding I didn’t need it after all.

Good luck


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