Thread: advice on dust extraction system, layouts etc.

Locating the DC outside the shed is a good idea but I hope no one needs to work in the garden shed for more than a few minutes as it will eventually become full of fine dust.

What DC you "need" depends on what your'e trying to achieve.

Do you want to reduce the amount of relatively harmless visible saw dust in your shed, or are you interested in minimising the invisible fine dust that has potential health implications.

To achieve the former pretty well any small DC will reduce the amount of sawdust.

To achieve the latter a nominal flow rate of 1000 CFM is required.
Using conventional DCs this can only be done with a nominal 3HP or greater DC using 6" ducting.
In addition any machine duct outlets must be enlarged to allow the outlets to directly accept 6" ducting.

Routers and circulars saws are better served by a vacuum cleaner (VC) but unless the VC is mounted outside a shed they can create more fine dust than they capture. To be mounted outside a shed a reasonably beefy (2HP) VC is needed and 50 mm ducting should be used.

If you can only afford one dust control machine then I would recommend a DC over a VC because at least a DC can capture some duct from portable power tools and vent your shed of residual fine dust far quicker than a VC.

Not everyone can afford a 3HP DC or have the power supply needed for these DCs, so a budget level compromise could be something like a modified 2HP unit such as I describe here https://www.woodworkforums.com/f200/g...ml#post1731209.
One problem with even the modified 2HP unit is the ducting runs need to be kept short i.e. <3m to be effective and the bags have to be kept clean.

Auto Start/delay off features are useful for venting dust that escapes initial capture.
The delay off is the most critical factor since this vents a shed of residual dust.
The delay off time varies depending on DC being used, materials, machines, methods etc
Small (1HP) DC basically need to be left running from the first dust making activity until the worker leaves a shed.
Larger DCs would use times of a few minutes to a few 10's of minutes - since this is so variable you would need an electronics delay timer to control this.
Setting a delay before starting the work is of limited value since you don't always do the work you intended so it would be better to set a delay afterwards.
I just leave my DC running and turn it off when I think - oh that's been on long enough.

Another option would be to use the DC to remove most of the dust at the source and add an extractor fan at the back of the shed so that any fine dust that is floating in the air will be sucked out. If you do your sanding/cutting near a door then between the DC and the extractor they should form a draft that blows the fine dust away from you. I used to use a largish 15" fan for my greenhouse, it was from the back of a large commercial heat exchanger, it is about 350watts but can suck out about 100 cubic meters of air a minute, used to make a nice gentle breeze though the large greenhouse. A small shed like yours would have a stronger breeze.

Cheers

Ed.

Originally Posted by Ed..

I used to use a largish 15" fan for my greenhouse, it was from the back of a large commercial heat exchanger, it is about 350watts but can suck out about 100 cubic meters of air a minute, used to make a nice gentle breeze though the large greenhouse. A small shed like yours would have a stronger breeze.

These axial type fans are not really designed for flow but to stir up air. Under zero restriction they end up turning over a substantial amount of air located in their immediate vicinity i.e. they suck air back into themselves that they very recently blew out, but this is not what you want for extracting dust. As soon as these fans are placed in situation where they are even slightly restricted i.e. they are asked to pull air through an opening of some kind and through a building, their flow rates will drop.

If you have one already and you don't mind the noise then they are cheap to run and are a good option, but otherwise I would recommend running a DC with all the blast gates open.

With the one I had in the greenhouse, I built a shroud over the blades and it worked really well and that fan moved a huge amount of air out of it, the other end of the green house had an opening with a water curtain and the breeze blowing through the mist cooled the greenhouse down. The shroud stopped the expelled air from coming back around, as it was mounted into the wall, the air had to come through the water curtain at the other end with a 4m x 1m opening. I have a similar shrouded fan removed from an industrial air conditioner ( as it is quieter at night but nowhere near the volume) mounted in my laundry room ceiling, for hot days in the late afternoon when it ends up being cooler outside than inside the house and there is no breeze, open some windows, switch it on and cooler air blows though the house as a breeze, cools the house down quickly. A small 3.8m by 6m shed should pose no problems getting a good breeze to blow through. My greenhouse is about 380 cubic meters and it did the job. for a shed it doesn't have to make a gale force wind, just enough to suck out the fine dust suspended and floating around in the air away from you and out past the fan.

I would still use a DC to collect the majority of the course sawdust and most of the fine dust but this is an addition to it, to remove just the fine dust that escapes it.

Cheers

Ed.

Originally Posted by breakerboy2000

which machine would be best for the length of duct run and for my future tools etc.

Breakerboy,

Fifteen months ago I had a serious dust problem. As I waded through the possibilities (and my dust) to fix the problem a wish list was drawn up:

1. I wanted a ducted system so I was not dragging machines around the workshop.
2. I wanted to vent outside (no bags or filters to clean/replace).
3. I wanted a small footprint (so I could keep the system in the shop and did not need to build a shed outside for a dusty).
4. I wanted to achieve the magic numbers of 800 and 4000 so I had a shot at capturing the very fine material and at avoiding clogged lines.

I bought a ClearVue cyclone. They are not a cheap installation, but it was the only system that ticked all the boxes on my wish list. The ClearVue is the best small shop dust collection system around, followed by the 3 HP dusty. Either of these can be ducted. The most cost effective solution is an optimised 2 HP DC (see BobL's link), but it won't work satisfactorily with ducting.

I bought a CV 1800, but if I had my time again I'd get the more powerful CV Max. Shedman is the Oz distributor. If you are interested, give him a yell. If you are thinking of going down the 2 or 3 HP DC path, give BobL a yell.

BobL is our resident dust extraction guru. His advice is always worth listening to.

Cheerio!

John

EDIT: Having a separate room in which to plonk your system should help a lot with noise reduction. The larger and more powerful units needed for a ducted system are NOISY.

Take a look at Bill Pentz's site for good info about dust collection ... Dust Collection Research - Home