Thread: Can a Dust extraction be too efficient?

I wouldn't worry about it especially as you have a separator. I don't have a separator and have had dozens of "bits" hit the impeller over the 11 years I've had my DC, still works fine.

I would avoid using a permanent grille as stuff will get caught up in and they can be a PITA to clean up. If you are going to use a grille make sure it's easily removable for cleaning.
Maybe look at this
Bell mouth hood offer - expressions of interest

I wouldn't worry about it especially as you have a catcher.

My DC is now 11 years old and I don't have a catcher, and dozens of wooden pieces have gone through the impeller. I had the imp out for a motor upgrade in 2018 - impeller still looks pristine.

If you are going to put mesh guard on any intake then make you can easily get at it for cleaning as it will pick up "stuff"
Bell mouth hood offer - expressions of interest

My testing has show that the finest mesh to minimise flow loss is about 25mm square , any finer than this really starts to impact the flow.

Thanks BobI sent you a private message about a question about what would happen if anything if I accidentally turn on the Dust Extraction with all the blast gates closed?

Originally Posted by tomartomau

Thanks BobI sent you a private message about a question about what would happen if anything if I accidentally turn on the Dust Extraction with all the blast gates closed?

Strange I did not receive anything.Back to your question, it depends if you have the DC in an enclosure or not.If the DC is not in an enclosure, with all the BGs closed you can run the DC indefinitely . With the BGs closed the DC motor will draw significantly less (yes less) current than when all the BGs are open as the impeller is not moving much air - its just rotating a few 10;s of grams per second of air inside the impeller. In contrast when the blast gets are open and 1000 CFM is going thru the impeller that means its shifting about 1/2kg of air PER SECOND so it has to work harder and draws more current.However, if the DC is in a vented enclosure the air from the DC will be vented out of the enclosure (other wise enclosure would blow up) and in doing so will drag heat away from the motor. If the BGs are closes there will be no air stream through the enclosure and hence the motor won't cool as easily - if you let the DC run for too long on a hot day it could overheat the motor.This will give you an idia of timescales. The air coming out of a DC is usually 1-3ºC hotter than the air dragged into a machine port from the shed. Some of this is heat from the machine where the dust is being extracted and some is the breaking of wood fibres by the cutting/scraping/sanding action of the machines. The DC motor itself is a significant source of heat which needs to be removed by the DC motor fan blowing cooling air across the motors external fins. But if it's the same air then that air will just get hotter and hotter.Here's is an exampleIm my enclosure with all the BGs open the DC motor draws about 9.5A and takes about 15 minutes of constant use for the motor temperature to rise by about 10 -15 degrees and after that it tapers off and does not get much hotter even if I run for longer. If the BGs are closed the motor only draws about 4A but the temp rises quicker (ie 5 minute stop increase by 10º) and it increases further. On a cold day it will probably be OK even indefinitely but on a hot day the motor could overheat. Some single phase motors have a temperature fuse on then which will protect the motor but constant hot running even if it doesn't trip the temp fuse could degrade motors insulation and lead to failure.

all interesting stuff .... i got a new dust extractor several months ago which is a big improvement on my old system ...

BUT at the router table which has a downdraft box connected to a four inch hose and a two or so inch outlet behind the router bit, i found recently when i was routing a dovetail groove in a flat panel that the suction was so strong i couldn't push the panel across the router table (maybe i am just old and weak) ... i opened another four inch outlet with nothing attached and it still gave resistance to being pushed but could go easily enough .. i had noticed before with edge routing pieces that there was a definite resistance to pushing but until the flat panel i had never thought about that problem

regards david

Originally Posted by robbygard

all interesting stuff .... i got a new dust extractor several months ago which is a big improvement on my old system ...

BUT at the router table which has a downdraft box connected to a four inch hose and a two or so inch outlet behind the router bit, i found recently when i was routing a dovetail groove in a flat panel that the suction was so strong i couldn't push the panel across the router table (maybe i am just old and weak) ... i

Have you tried waxing the table and fence.

i use silbergleit on the table regularly .. i will try a wax if i need to do that again ... thanks

regards david