Dust Collection (again) - Shop Vac Help Please


Help Support UKworkshop.co.uk:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.


Established Member
18 Feb 2011
Reaction score
Switzerland, near Basel
Gents, I'd appreciate any guidance you can offer on the following.

Having just been lucky enough to get hold of one of Steve Maskery's cyclones, plus having found a decently-sized metal dustbin cheap at the local DIY Emporium, I obviously need to couple it all up to my existing shop vac. It's a Karcher and apart from the horrendous noise it makes I'm very pleased with it 'cos "it sucks like a goodun". I tend to use it for fairly lengthy periods (30+ mins perhaps) and so my first question is:

1. When running am I correct in thinking that internal heat (within the vac) will be dissipated when I run the vac with the "blower hole" open? That's my present practice and this does NOT seem to materially affect the powerful suction - at the end of such session both the exhaust air and the outside of the motor head are definitely a bit hotter than just "warm", but in my judgement, nowhere near excessively so.

2. Because of the present high noise level, and as when the cyclone is connected I guess I'm likely to run it for even longer sessions than the above 30 mins at a time, I'd like to build a small enclosed cabinet with baffle to reduce noise - as per several examples seen on the internet. My question is, will such a cabinet be likely to reduce the life of the vac (it's already several years old) due to higher heat that, surely, must build up within the cabinet?

Any pointers gratefully received.


Not sure what blower hole you're referring to? Do you mean the exhaust hole? All vacs have & need this - the air has to exhaust somewhere!

Heat in a vac is caused by the motor working too hard - either due to a blockage or dirty filters and the like. Of course there will be some heat generation through the normal running of the vac.

As long as your silencing solution allows for the exhaust air to flow reasonably well, it shouldn't impact the life of the vac considerably. It's worth periodically checking the temp of the motor housing though, especially after a long session
Thanks for the input Matt.

The Karcher has 2 holes to connect the hose into - one's a "sucker hole", the other is a "blower hole" (e.g for blowing dust, or perhaps leaves in the garden I guess). The blower hole also has a slider whereby you can adjust that hole from fully closed to fully open. That is separate to the "real exhaust" which exits the vac by means of slots at the bottom of the casing.

Just as you say, the exhaust air coming out below the machine is warm/hot, and if the blower hole slider is opened at all, so is the air coming out of that hole - approx the same temp I would say.

Because the "manual" doesn't say anything at all about duty cycle, when running the vac for long-ish periods I've been running it with that blower hole slider fully open, and it's really only the loud noise that causes me to shut it down after, say 30+ mins.

As per my OP, having that blower hole open does not seem to reduce the strength of the suck as far as I can tell, and also as per my OP, the temperature of the exhaust air from both the exhaust lower slots and from the blower hole doesn't seem to be higher than when running with the blower hole slider fully closed.

I'm probably worrying about nothing because, also as per my OP, the exhaust air and the top of the motor housing are not what I'd call excessively hot.

P.S. The filter is not blocked and I empty the paper bag once it feels full.


Ah, I see. I assume that all it does is redirect the exhaust air from the real exhaust to the blower port, which is why it doesn't affect suction.

So leave it open or closed when putting it in your silencer - shouldn't make a difference :)

My vac exhausts from the port only, rather than having a separate exhaust.
Thanks Matt. (BTW, in another life, L O N G ago) I used to live in Lingfield).

Anyone else have any pointers or inputs re making a noise reduction cabinet?