Dust Collection - Outside Exhaust

[John Akerblom]

Hi,

I am putting together a little workshop in the garage of a house I just moved into. I am running a TS, lathe, miter saw, and will be adding a bandsaw, a router table, and maybe have room for one other tool. I am trying to figure out the best way to collect all the dust.

My main concern is getting a powerful enough DC to actually suck up the dust from each tool (including fine particles). My second concern is cost (my budget is flexible, but I don't want to buy anything I don't need [see below re: external exhaust])

I noticed a lot of the issues on these forums have to do with a loss of suction due to filter clogging. I have a nice concrete space behind my garage where I am planning on building an MDF cabinet around the DC. I'll line the MDF with sound deadening insulation, and then create some sort of baffle to exhaust air efficiently while deadening the sound. I plan to run the intake PVC pipe through a hole I will cut in above the garage's rafters, then create a system of PVC in the garage to minimize the suction loss (6" ridgid PVC reduced down to 4" with blast valves at each tool [using a minimum of flexible hose]).

Therefore, since I can exhaust air (and fine dust particles) directly into my backyard, all I really need is a powerful motor, and some sort of cyclone/separator to collect the chips and thicker particles into a waste receptacle.

Does anyone have any good ideas on a good setup to operate within these parameters? Almost all of the ready-made systems I have looked at focus a lot on the filtration system, while all I really need is a chip collector and a powerful motor/strong impeller. Any and all guidance (and pointers to other threads that have addressed this) would be greatly appreciated.

Thanks,
John

[Julie Moriarty]

I have a Delta drum type dust collector that I modified into a cyclone DC. I've always exhausted outside. Before the cyclone mod, a LOT of waste spewed out on the lawn. Since the mod, all there is is some fine dust that vanishes in the wind. Here's the thread for modifying a drum DC to a cyclone: http://www.sawmillcreek.org/showthre...Dust-Collector

[Steve Kinnaird]

You mentioned building the walls out of MDF. Is this and enclosed area or outside?
MDF will not hold up to moisture.
Get a good 2HP or better DC.
Setup the cyclone separator and where the blower motor would normally go to the filter and collection bag, just direct it outside.

[John Donhowe]

There's a lot of good info on Phil Thien's site (jpthien.com) about effective dust separators. One thing to be aware of is that sound insulation material is also usually thermal insulation, so be aware that you might have a lot of motor heat buildup in your cabinet unless you provide good ventilation.

[James Gunning]

If you want proper dust collection from the start, the answer is a cyclone with a large enough motor and impeller and large enough piping (6" or greater) from your machine to the cyclone. Anything else is just an intermediate step on the way to finally getting the cyclone. Strongly suggest you look at Bill Pentz website and read the material there. http://billpentz.com/woodworking/cyclone/

Exhausting outside is actually the best way to handle the cyclone exhaust from the dust collection angle, but be sure you are allowing for the make-up air that exhausting outside will cause. You will be blowing out part of your heated or air conditioned air. Also, make sure you are not pulling fumes from a water heater or furnace into your shop.

[David Ragan]

If you want proper dust collection from the start, the answer is a cyclone with a large enough motor and impeller and large enough piping (6" or greater) from your machine to the cyclone. Anything else is just an intermediate step on the way to finally getting the cyclone. Strongly suggest you look at Bill Pentz website and read the material there. http://billpentz.com/woodworking/cyclone/

Exhausting outside is actually the best way to handle the cyclone exhaust from the dust collection angle, but be sure you are allowing for the make-up air that exhausting outside will cause. You will be blowing out part of your heated or air conditioned air. Also, make sure you are not pulling fumes from a water heater or furnace into your shop.

Excellent advise-all of it.

[Jim Andrew]

Before you buy a dust collector, be sure you look at the size of the impeller. The bag units typically have smaller impellers than the cyclones. The biggest bag unit is the 3hp Jet or Powermatic, same unit, with a 14" impeller. The Grizzly cyclone units appear to have bigger impellers than comparable units except for Clearvue. Some of the companies don't even post the size of their impellers.

[glenn bradley]

Ah dust collection threads . . . so much discussion, so much information

You are ahead of the game in that you have your desired end in focus. Many folks have added cyclone to systems not designed for them and have had some success. In high school folks would put V-8's in Volkswagon buses but, the drive train would fail somewhere soon after. My point being that if you are starting from scratch you don't have to try to make a non-cyclone blower work a cyclone. there is more science in air movement than I will ever understand but, we all know the old saying about the right tool for the job.

Your blower will match the cyclone it is designed for. If I were in your enviable position of being able to vent outside I would simply duct my current cyclone outside and skip the filters. I suggest yo do the same. Others will have many other opinions and suggestions .

[Dan Friedrichs]

I vent outside, and it's great (if you live in a climate that can tolerate the heat/cold loss - which is not as big of a problem as you might initially think). You don't even need a cyclone - a separator (like Phil Thien's design) is more than sufficient.

The noise issue isn't as severe as you might think, either. I'd highly recommend trying the blower to assess the noise level before you begin building an enclosure.

Acquiring just a blower/motor might be tricky - I'd recommend watching craigslist for a used bag-type unit, then just removing the bags.

As others have said, you are wasting capacity if you neck the 6" main lines down to 4" at the tool. The frictional losses in 4" vs 6" line are negligible - if you neck down to 4" at the machine, you might as well use 4" pipe throughout (assume you're a small one-man shop only running one machine at a time). And using 4" throughout is a horrible idea - so find a way to modify machines to accept a 6" port.

[John Donhowe]

if you neck down to 4" at the machine, you might as well use 4" pipe throughout (assume you're a small one-man shop only running one machine at a time). And using 4" throughout is a horrible idea - so find a way to modify machines to accept a 6" port.

With all due respect, I must disagree with these comments. There are two major factors in dust collection: air flow (cfm) and air speed (fps), and duct system design is a compromise between the two. Larger ducts reduce resistance to flow, to improve air flow, but the air speed in the duct decreases- air speed = air flow/duct area. You need about 3000 fps air speed to keep typical wood particles moving in horizontal duct, but 3800 fps to pull them vertically (as with most systems with duct drops from an overhead horizontal trunk). So, your blower might be able to produce 3000 fps in 6" duct, but the only way to get up to 3800 fps is to go to 4" duct to avoid clogging.

Also, running 4" pipe throughout is not the same as running 4" for a short length and connecting to 6". By analogy, running a short 16 gauge extension cord to a 12 or 14 gauge circuit outlet is not the same as running a super long 16 gauge extension all the way back to your electrical service panel.

There are many collectors that simply are not powerful enough to generate sufficient air speed in 6" ducts, so the only option is to use 4" in the whole system.

[Dan Friedrichs]

I agree, John - my statement was excessively generalized, and I'm assuming (perhaps wrongly) that the OP is looking at a 3-5HP collector, without any filters, which would be capable of supporting sufficient velocity in 6" pipe. My point was that for a ~5HP collector (what many would consider the "ideal" size), used in a home shop, performance from a system done with 6" mains and 4" drops is more similar to a system done entirely in 4" than a system done entirely in 6". I haven't done the analysis, but intuitively, I think for the lengths of pipe and air speeds we're talking about, the frictional losses are not significant - but since most users are seeking maximum CFM, the use of a reducer trades CFM for velocity, which is generally undesirable.

[John Donhowe]

On same page with you, Dan.

[Dan Friedrichs]

On same page with you, Dan.

I thought no one was allowed to agree on this topic

[William A Johnston]

John I just went through a similar situation. I took my 2hp single stage collector and modified it with a cyclone seperator from Saratoga cyclone seperator and vented outside. It works like a charm. I put gates at all machines and open as needed. Improved the performance is the system greatly. I have about $350.00 in the seperator and stand. I had the 2hp unit already. No more filter clogging or filter resistance.

[Allan Speers]

With all due respect, I must disagree with these comments. There are two major factors in dust collection: air flow (cfm) and air speed (fps), and duct system design is a compromise between the two. Larger ducts reduce resistance to flow, to improve air flow, but the air speed in the duct decreases- air speed = air flow/duct area. You need about 3000 fps air speed to keep typical wood particles moving in horizontal duct, but 3800 fps to pull them vertically (as with most systems with duct drops from an overhead horizontal trunk). So, your blower might be able to produce 3000 fps in 6" duct, but the only way to get up to 3800 fps is to go to 4" duct to avoid clogging.

Also, running 4" pipe throughout is not the same as running 4" for a short length and connecting to 6". By analogy, running a short 16 gauge extension cord to a 12 or 14 gauge circuit outlet is not the same as running a super long 16 gauge extension all the way back to your electrical service panel.

There are many collectors that simply are not powerful enough to generate sufficient air speed in 6" ducts, so the only option is to use 4" in the whole system.

I seriously question that last part, though I am so expert and you may be correct. The way I understand it, if the main pipe is sealed, then makiing t as wide-diameter as possible is ALWAYS better as this reduces pressure on your blower.

Since we're doing analogies, it's like sending water to a sprinkler head vias a 1/2" hose vs a 3/4" hose. That sprnkler's inlet diameter is the limiting factor, but a 3/4" hose will result in a much more powerful spray.

Analogy #2: When I clean the floor with my Festool CT36, I use a nozzle that has a 1.25" opening. I used to use the narrow hose that came with the saw, and which works well with my sander. However, switching to a 4" diameter hose made a HUGE difference in how much that nozzle sucks up.
I think that when the large diameter / low air flow chamber suddenly becomes a narrower outlet (from the tool, this creates the air speed that we need, and there's probably some math involved there. But again, my understanding is that the larger the main trunkline, the better.
If someone knows FOR SURE that this is incorrect, I'd very much like to know.