Festool Pro 5 sander

[Van Huskey]

Those speed control devices are made for universal motors and have been used for many, many years. If there was a problem where they damaged the motor, we'd have heard about it by now.
Second data point: I've been running my vac for years that way and it works just fine.

Look at this page, part way down. I have a picture of my setup.

Mike

Zero issues electrically but there is the potential heat dissipation issue with VERY extended runs time, something you would never see with a router but just MIGHT with a vac, this of course is due to the fan being sized and shaped for full rpm, that said I wouldn't think twice about doing it keeping in mind not to run it for hours at a time non-stop.


To the OP, as stated there is no magic to the Festool vacs, the move air like the rest of them. You indeed do need to use a vac with a Domino, not a suggestion but an absolute for ship removal, unless you like replacing bits.

Even though they aren't magic the Festool extractors do have a lot of benefits some of which are available in other brands.

Very quiet
Auto on off
Variable suction (mainly useful with sanders)
Full unit HEPA certifications (a big one in my book)
Systainers stack on them or the CT SYS which is in a Systainer
A cornucopia of accessories and add ons that can make life easier
high quality hoses that if you use mostly Festool tools connect without the need of a bunch of adaptors and jury rigging

My opinion is if budget allows buy a Festool DE you will likely never regret it and buying with a tool gets that small but useful discount. Also I suggest getting the Domino assortment, while it looks overpriced at first glance it is actually a very good deal that is hard to come by with Festool.

[Mike Henderson]

One thing that helps with a fan (which a vacuum is) is that the power consumed by the motor goes up by a power factor as the speed of the fan increases. I'd have to check sources, but my memory is that the power is 3. So if you cut the speed by two, the power drawn by the motor goes down a significant amount. And when you reduce the power drawn by the motor, the heat goes down significantly.

If I'm right about the power factor being 3, the watts consumed would go up by 8 when you doubled the RPMs. But even if the factor is 2, the watts consumed would increase by 4 if you doubled the RPMs. And watts in is directly related to heat.

There are some really good motor people on the forum so I hope one of them will chime in with the correct information.

Mike

[Here's a web page that discusses it.]

[Van Huskey]

One thing that helps with a fan (which a vacuum is) is that the power consumed by the motor goes up by a power factor as the speed of the fan increases. I'd have to check sources, but my memory is that the power is 3. So if you cut the speed by two, the power drawn by the motor goes down a significant amount. And when you reduce the power drawn by the motor, the heat goes down significantly.

If I'm right about the power factor being 3, the watts consumed would go up by 8 when you doubled the RPMs. But even if the factor is 2, the watts consumed would increase by 4 if you doubled the RPMs. And watts in is directly related to heat.

There are some really good motor people on the forum so I hope one of them will chime in with the correct information.

Mike

You are correct that need for heat dissipation drops dramatically at lower rpms BUT the fan efficiency (for a motor designed for a fixed speed) usually drops much faster. The blade size and pitch is designed for a certain rpm and for a universal vac motor the speed is HIGH. Again, it would only be an issue if the vac was run for very long periods of time, far longer than most home shop situations would call for, but I think it is a fair caveat to keep in mind but it may be a more hypothetical vs practical concern, but thermal management is not a strong point for universal motors to begin with, which is why you almost never see a TEFC universal motor.

[Mike Henderson]

You are correct that need for heat dissipation drops dramatically at lower rpms BUT the fan efficiency (for a motor designed for a fixed speed) usually drops much faster. The blade size and pitch is designed for a certain rpm and for a universal vac motor the speed is HIGH. Again, it would only be an issue if the vac was run for very long periods of time, far longer than most home shop situations would call for, but I think it is a fair caveat to keep in mind but it may be a more hypothetical vs practical concern, but thermal management is not a strong point for universal motors to begin with, which is why you almost never see a TEFC universal motor.

Again, I'm going from memory, but I think the efficiency of universal motors is fairly constant over a wide RPM range. Not that it doesn't drop but the drop is not precipitous.

I'm not a motor guy and there are some people on the forum who are - I hope they'll chime in.

Mike

[Van Huskey]

Again, I'm going from memory, but I think the efficiency of universal motors is fairly constant over a wide RPM range. Not that it doesn't drop but the drop is not precipitous.

I'm not a motor guy and there are some people on the forum who are - I hope they'll chime in.

Mike

I am not suggesting the efficiency will drop significantly (at least in the rpm range I suspect we are discussing) nor am I suggesting the amount of heat from the motor will not reduce significantly, what I am suggesting is the amount of airflow from the motors fan may well drop at a faster rate than the heat produced. The blade size, shape and pitch will be optimized for full rpm. Again, this is hypothetical and may have little impact in practical use, and even if it does a specific motor may be able to handle a significant increase in operating temperature without ill effects, it is the one potential issue that is usually raised in discussions when using speed controls on equipment designed as fixed speed, this extends to the routers they were developed for but again sustained full load on a router for long periods of time is extremely rare.