All Replies on dust collection outside venting

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View bbrown's profile

dust collection outside venting

by bbrown
posted 02-17-2018 02:59 AM

13 replies so far

View WhyMe's profile


1177 posts in 2066 days

#1 posted 02-17-2018 03:20 AM

There is a grid on the intake so real large stuff won’t go through to the fan. The normal function of the collector passes chips through the fan.

View Woodknack's profile


12903 posts in 2886 days

#2 posted 02-17-2018 03:27 AM

Over time, yes it will cause damage. Expect to replace the fan in several decades.

-- Rick M,

View CaptainKlutz's profile


1883 posts in 2000 days

#3 posted 02-17-2018 06:46 AM

Has long as you do not use a wide open 6” intake to blower, a direct unfiltered exhaust should be fine.

FWIW – The blower motor is designed to have some static pressure loss. For discussion purposes does not really matter if restriction is on suction or exhaust side. Without “typical” expected pressure loss, the motor/impeller can spin freely and will draw more power than design intended. This will eventually lead to overheating, or maybe even trip breaker. The industrial motors used will take large amount of abuse, and will appear to work with minimal static pressure despite drawing up to 50% more power than rated, till they melt.
Can easily test if your duct design will be safe for motor long term by measuring current draw when running with normal number of gates open. If the motor current draw is significantly over the name plate rating, you need to add some more pressure loss to the system (or close some gates) to keep motor happy.

Probably do not need to worry about adding a restriction, but better to know then be surprised when overheating happens. Adding needed restriction can be as simple as using a reduced size exit pipe, or simply using 4” or 5” ports on your tools/gates. Using flex hose also adds tremendous amount of static loss.

-- I'm an engineer not a woodworker, but I can randomly find useful tools and furniture inside a pile of lumber!

View bbrown's profile


272 posts in 4058 days

#4 posted 02-17-2018 11:57 AM

Thanks for the input. I’ll have 4” blast gates on 4-5 machine with 5” main duct, all going directly via a fairly short run to the Harbour Freight 2 HP motor/impeller mounted high up on the wall or ceiling. These blast gates might provide the necessary resistance? My plan was to vent directly outside to an unobtrusive area. I just was not sure that I’ve seen any one doing that and figured there might be a reason no one’s doing it that I should know about.

I suppose it’s easy enough to add one of those Thein-type trash can chip collectors immediately before the motor, but I’m looking for quick and easy here. Like I said I’ve got no close neighbors to worry about and I can clean up the chips.

-- Micah 6:8

View Jacksdad's profile


238 posts in 930 days

#5 posted 02-17-2018 12:41 PM

Here’s my two cents, I know two professional woodworker who vent their dust collectors outside, one has a small building with a wagon under the pipe and the other has an old pick up truck with big box sides on it. Both run the dust collectors 6 to 10 hours a day without problem, plus they sell the sawdust as animal bedding, not walnut dust. The only drawback is you are pumping your heat outside through your dust collector hose, but it works great.

View Fred Hargis's profile

Fred Hargis

5738 posts in 2999 days

#6 posted 02-17-2018 12:49 PM

Frankly, I think you will be OK no matter what you do, but having an amp meter takes out all the guess work.

-- Our village hasn't lost it's idiot, he was elected to congress.

View johnstoneb's profile


3128 posts in 2678 days

#7 posted 02-17-2018 02:39 PM

I would put a separator in the system or something to collect the chips outside as it can get real old cleaning up and the chips and sawdust can make a real mess.

-- Bruce, Boise, ID

View bondogaposis's profile


5538 posts in 2857 days

#8 posted 02-17-2018 02:52 PM

There is nothing wrong with doing this unless you are heating your shop. The collector is rated at 1550 cfm. So even if your duct work cuts that in half You will be losing 775 cubic feet of heated air every minute. That air has to be replaced somehow and it will be coming in from the outside. It will drive you heating costs up quite a bit and make your shop colder to boot if your heating system can not keep up.

-- Bondo Gaposis

View bbrown's profile


272 posts in 4058 days

#9 posted 02-18-2018 01:47 AM

Thanks for the feedback everyone. I’m in Virginia and even on very cold days do not have to heat my basement shop. So heat loss is not an issue I worry about. In summer it stays fairly cool as well even without A/C.

I am a hobbyist so my big machines don’t get much use.

I’m 60 and should have done something about dust collection 30 years ago! I usually open the shop door and have a big fan on wheels that sucks the dust outside. It’s’ not been ideal for the lungs. So, better late than never for a real system.

Is it OK to use a 4 inch main duct as well as 4 inch connectors to my machines? The total length of the main run would be about 20 feet and the connectors to my machines coming off the main would be fairly short. That would make my system even simpler. All’s I would need is some PVC (I read that sewer pipe PVC is as good at half the price), some blast gates, and the HF impeller venting outside. Not sure if i’m missing anything here. I gather that the impellor can withstand planer sized chips flying through it?

We’ll see how it works. I can always add a separator, etc. down the pike.

-- Micah 6:8

View Fred Hargis's profile

Fred Hargis

5738 posts in 2999 days

#10 posted 02-18-2018 12:34 PM

4” will be fine for that collector as will the PVC. Yes, the impellers will withstand the small stuff hitting it, it’s when a good size chunk of wood (or nuts/bolts and other miscellaneous debris) hits it that you have problems.

-- Our village hasn't lost it's idiot, he was elected to congress.

View jonah's profile


2078 posts in 3804 days

#11 posted 02-18-2018 01:08 PM

The HF collector really isn’t powerful enough for long runs of ducts and multiple machines. It’s best used as a roll around collector as close as possible to the machine in use. It has a very small impeller and just doesn’t move that much air. 1550 cfm is a joke – you’re lucky to get half that out of a HF unit.

View bonesbr549's profile


1584 posts in 3573 days

#12 posted 02-18-2018 01:41 PM

The guy I bought my lumber from back in IL, had a similar set up for his shop. He had some big industrial motors and a rig set up and shot it outside his building. He had a monster pile of SD. There was a lady in his area that had horses, and she would come by and fill up her pickup and haul it off for him. Great set up.

-- Sooner or later Liberals run out of other people's money.

View bbrown's profile


272 posts in 4058 days

#13 posted 02-18-2018 04:40 PM

There’s a horse farm across the field who takes my chips. From my reading, I think the HF motor should be plenty powerful to handle my small shop. It seems that folks commonly use the same 2 HP blower for bigger tasks than mine. I plan to have just one 20 foot 4” main duct, with 4” flex hose to each machine. Only one machine ever in use at a time. Impeller/motor on the wall exiting outside. I’m thinking that a separator will be a good idea to prevent too much outside cleanup and prevent damage to the impeller.

Hoping I can accomplish all of this for under $200, not including the HF collector which I already have.

-- Micah 6:8

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