Comparing shop vac and dust extractor performance (data included)

[Dan Friedrichs]

Whenever I bring my shop vac indoors to clean up from a "project", I find myself wanting something similar for indoor use - it moves a TON of air, which seems very handy for dusting, vacuuming hardwood floors, powering turbo carpet brushes, etc.

I had tried using my Festool CT-Mini for this, but subjectively it felt like it moved no where near as much air.

I had access to a thermal anemometer, so took measurements of my Ridgid 14 gal shop vac (with aftermarket HEPA filter)(vac is rated 180 CFM by Ridgid), and my Festool CT-Mini (rated 130 CFM by Festool). I used both a 2.5" diameter hose and the Festool 32/27mm tapered hose on both.

Here's the results:
vac_plot2.jpg

Note that I only measured over the range of 0-15" static pressure, because if you're using one of these as a vacuum, you're trying to move air (not lift bowling balls), so I don't see the point of taking measurements at 0 CFM and 100"....

Both vacs had new bags / clean filters.

I'm disappointed at the result, to be honest. I was thinking of buying another Festool vac for general shop clean up (to replace the Ridgid), but the Ridgid moves significantly more air (and is a fraction of the price). And it has an aftermarket HEPA filter. I really wish some company would build a vacuum with as much suction power as the Ridgid, but with a 1gal container!

For completeness, I also took measurements of other household vacuums I had access to. For these, I used a smaller-diameter measuring tube (~1", instead of 2"):

vac_plot1.jpg

Interesting results here are that the Makita backpack vacuum is comparable to the little dustbuster/stick vacuum. And with this lower SP range and using the 32/27mm hose, the Festool and Ridgid are comparable (which the other plot indicates, as well).

So I guess I'm keeping the Ridgid for cleaning the cars, shop, etc.

[John Lanciani]

Looks clear as day that the 32-27 hose is the real issue. It appears to be limited to 50-55 cfm no matter how hard the vacuum sucks.

[Dan Friedrichs]

Looks clear as day that the 32-27 hose is the real issue. It appears to be limited to 50-55 cfm no matter how hard the vacuum sucks.

Yep, absolutely. So I guess it's saying that if you're using a ~27mm hose for dust extraction (from a sander, for instance), you could use either a $99 shop vac or a $500 "dust extractor" and get the same performance.

I was hoping that the CT-Mini would move more air when connected to the 2.5" hose, though.

[Jim Becker]

Devices like the CT Mini are optimized for extraction from small tools, not for general shop cleanup. You will get better performance with the larger hose, however....you can fit more air in it. "Duct size" counts. That's not saying anything negative about the Rigid vac...it's a good product and I have a couple of them for general cleanup. I use my Festool CT-22 exclusively for extraction from small tools in the shop.

[Dan Friedrichs]

Devices like the CT Mini are optimized for extraction from small tools, not for general shop cleanup.

I've always heard this, which was really the impetus for testing this. I think my first plot contradicts that statement, though. When using a 32/27mm hose like you'd use for extraction with small tools, it appear the Festool and Ridgid perform almost the same.

[Rod Sheridan]

Yep, absolutely. So I guess it's saying that if you're using a ~27mm hose for dust extraction (from a sander, for instance), you could use either a $99 shop vac or a $500 "dust extractor" and get the same performance.

I was hoping that the CT-Mini would move more air when connected to the 2.5" hose, though.

Only if airflow is your only consideration Dan.

I find the Festool vac great for sanding. At work we use it with the 50mm hose for cleanups, with the smaller hose for tool extraction.

We also use Nilfisk vacuums.

The Festools like many have variable suction and auto-start, as well as being a HEPA vacuum, not just a vacuum with a HEPA filter (Big difference). The Festool also has good tool and hose storage, something a lot don't.

I've also used the Fein vacuum, another great choice...........Rod.

[Dan Friedrichs]

100% agree, Rod. I'm actually thinking of getting a new CT-26 because it's quieter and you can add that neat bluetooth on/off button at the end of the hose

[Peter Christensen]

I'm curious as to how you do the tests. Single point at the hose opening? With a test duct of some kind and measurements across the diameter to average the readings? Or another way? What brand/model of tester? Something affordable I hope? Thanks.

[Dan Friedrichs]

Peter, I bought lengths of 2.5" and 1.5" (ID) PVC pipe (roughly equivalent to the 50mm and 36mm Festool hoses I'm most interested in), and drilled holes in the middle of the lengths for the hot-wire anemometer probe and a static pressure pitot tube. A blast gate at the end of the pipe let me vary the air resistance.

I don't have the model number of the measurement instrument, but it was a multi-kilobuck lab-grade unit that you can program for a given duct ID and it will calculate the CFM based on the air velocity. Unfortunately, it's not affordable enough to live in my shop permanently...

[Frank Pratt]

I've always thought that the Ridgid shop vacuums were a great value as far as price/performance were considered. Certainly not as nice as the Festool, but if your budget is tight they are the ticket.

[Peter Christensen]

Thanks Dan I appreciate you taking the time to reply.

[Larry Frank]

With the hot wire anemometer, did you take measurements in just one place in the pipe. I have wondered when working with small diameter pipes how you overcome the pipe surface effects.

[Dan Friedrichs]

Larry, the hot wire anemometers I've seen (Dwyer 471 or similar) have probe tips that are probably 1" long, so once you put it into a small tube, there's not much room to move it, anyways. From what I could tell, slight movement didn't make much impact, so I just did my best to center it and didn't give it much additional thought.

[Matthew Hills]

a HEPA vacuum, not just a vacuum with a HEPA filter (Big difference)

What is the big difference?


Matt

[Larry Frank]

The difference is that with a HEPA filter you only have that and says nothing else about air and dust leaks. My Festool HEPA vac is well sealed everywhere on it with modest escaping. With my Ridgid vac with HEPA filter, the lid leaks and is not tight.