My question is simmilar to Will this setup severely reduce the CFM from my dust collector?

I have 2" ducting for a shop vac and a small dust deputy. I want to upgrade to a dust collector and 4" piping, but since it is my hobby i have limited time so need to approach in stages. I was thinking of mounting the collector first and hooking it up to existing 2" piping and then slowly replace piping with larger diameter.

I know all the differences between HVLP and LVHP, my question is more along the of am i risking damage to the collector motor itself?

  • I don't really know the answer, but if you're worried about it you can always just put a vent in the line right before the collector. Of course you'll have to balance the size to maintain adequate suction. Dec 18, 2018 at 22:23
  • I'm not convinced this is really within the purview of Woodworking, at least for the purposes of a SE site. While it discusses some aspect of shop tools, there is nothing specific to woodworking in how exhaust or dust extraction systems are designed I don't think. And while some folks here might have some insight into what is essentially HVAC knowledge, that knowledge isn't really required or limited to woodworking. I suppose there might be a way to provide refs to a "generally, this is the range of duct lengths vs. volumes vs. CFM ratings" table...
    – user5572
    Dec 19, 2018 at 17:17

2 Answers 2


A severe intake restriction should place less load on the motor than an severe exhaust restriction like a clogged filter.

If you have a dust collector where the motor is mounted outside of the blower housing, you should not have an issue. As the motor cooling is not dependent on the intake air volume.

You may not be risking damage to the dust collector motor, but its performance will be very poor if you have long runs of 2 inch pipe.


Central home vacuum systems use long runs of 2-inch pipe. The motors seem to always get bigger without changing the piping. A severely restricted intake would let the fan freewheel, and the motor speeds up slightly. It won't overload the motor.
If there is too much suction noise, you could build a diverter vent. You could baffle it and you could make it adjustable. Central vacuum systems have an output sound muffler that you could use as part of your intake diverter.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.