Cyclone/DC Outside Exhaust - Length?

[Keith Kelly]

I do woodworking as a side hobby, in a 2 car garage, and I'm making way too much dust. My first step is to reduce the amount of dust as it exits my tools, before it has a chance to get into the air.

My plan is to take the HF Dust Collector and turn it into a cyclone that exhausts to the outside. (this here: http://www.instructables.com/id/Maki...lect/?ALLSTEPS)

Situation: The natural place for the DC will be on the west wall. However, the natural place for an exhaust vent (dryer vent style) is on the east wall.

I'm under the impression that a long INTAKE run (to hook up to tools) would decrease suction performance. BUT, would a long EXHAUST run (30ft) decrease performance much?

(If I exhaust through the west wall by the DC, that's the sidewalk. This may be an option but I expect that I'll be getting a lot of dust on the sidewalk or side of house, and my house isn't ghetto yet, so I don't want to make it that way.)

[Duane Meadows]

With a cyclone separator, dust in the exhaust should be minimal. A post cyclone filter will reduce it even further.

Yes the length of the exhaust run will effect performance. I would think the amount would be just about as much as long intake run. Airflow resistance is airflow resistance.

Also, if you heat or A/C the space, you will be blowing a lot of energy outdoors!

[glenn bradley]

Dad just rigged his 2HP bagger to vent outside. The 5 feet of 6" pipe puts way more restriction on the unit than the upper bag did; not a good thing. We are looking at changing it to 10" at the exit. Your cyclone is already going to give you a big hit on airflow. I would recommend against a long exhaust run in addition. Basically if your lower bag is blown up like a balloon, you have too much back pressure. The bag can inflate but, should be very soft. Most commercial bags are way too small but, a properly sized bag gets pretty enormous (think bag-house), that's why folks move to pleated filters. JMHO.

[Keith Kelly]

With a cyclone separator, dust in the exhaust should be minimal. A post cyclone filter will reduce it even further.

Good call on the post-cyclone filter. That alone should eliminate the issue and allow me to vent towards the sidewalk. I think the problem is solved by this alone!

Yes the length of the exhaust run will effect performance. I would think the amount would be just about as much as long intake run. Airflow resistance is airflow resistance.

My hopes were that since it's not having to carry objects (wood chips) that it might be OK. But it sounds like the air flow resistance will still be substantial regardless.

Also, if you heat or A/C the space, you will be blowing a lot of energy outdoors!

Fortunately I'm not heating or air conditioning the space. (I've never said that before, and I don't think I ever will again. It's hot in there right now and I'd love some A/C)

Dad just rigged his 2HP bagger to vent outside. The 5 feet of 6" pipe puts way more restriction on the unit than the upper bag did; not a good thing. We are looking at changing it to 10" at the exit. Your cyclone is already going to give you a big hit on airflow. I would recommend against a long exhaust run in addition. Basically if your lower bag is blown up like a balloon, you have too much back pressure. The bag can inflate but, should be very soft. Most commercial bags are way too small but, a properly sized bag gets pretty enormous (think bag-house), that's why folks move to pleated filters. JMHO.

That's helpful.

Regarding lower bags... If it makes any difference, I won't have a lower bag, but rather a plastic barrel like shown in the link to the HF Cyclone instructable.


So, my current plan then is to vent directly behind the unit, and use a filter to make sure my guests and the UPS guy don't get their feet all sawdusty and splintery.

[Erik Christensen]

if you have a post cyclone filter then there is no need to exhaust outside - with the right kind of filter the return air is cleaner than shop or outside air.

[Mac McQuinn]

Make sure you don't have a noise/dust ordinances in your area. Things can get sticky pretty fast.
Mac

[Stephen Cherry]

The exhaust run will hurt just as much as intake, given the same duct size. The plus side is that it is under positive pressure, so you could go up to much larger hvac duct from the home depot. Don't need to worry about it collapsing because it is being inflated.

[Chris Parks]

Increase the size of the exhaust and the losses will reduce. Include a muffler in it and the noise will reduce as well. The exhaust on any cyclone should be larger than the inlet to reduce flow losses.