Warning: Controversal Subject, Venting DC Outside, Need Help Please

[Paul Richard]

Hi All,

Here is my situation... I have a basement shop and only work there in the colder seasons (live in NY Metro area), maybe 4-5 months and only on weekends a few hours at a time. I’m a hobbyist at best, but plan to spend more time there when I retire. I have a Grizzly 2HP, bag based dust collection system. I've done some duct work with standard 4" black pipe from the box stores with 4" flex hose for routing things to my machines. 3 drops support a table saw, jointer/planer and a third gets swapped between a router table, band saw and miter saw. I know there are lots of debates about grounding. My DC runs not more than 5 minutes at a time, so I don’t see it as an issue for me, and thus far it has not been - no shocks and no hair standing on end unless my wife calls me for dinner. :-)


In short, I have a LOT of the very fine dust in my shop and I want to get rid of it by removing the bag and exhausting outside. I know there are several threads on this subject - I've real virtually all of them, including Bill Pentz’s site at length. That said I think I want a separator before my DC, then a cartridge filter, then send everything else outside. I have two windows in my basement, one of which I can convert to an exhaust port. One is next to the furnaces (see below) the other (preferred) is under a deck that has a 3’ crawl space.


So, first, I wonder what folks think of this approach. I know this is a spirited subject, so feel free to tell me why my plan is genius or assinine. :-)


To complicate things, my shop is in a part of my basement that includes two oil fueled, forced air furnaces and an oil fueled hot water heater. My concern is that venting the air outside will create enough suction that I could pull carbon monoxide into the shop from the exhaust of the furnaces/water heater. I run the system now with the bag and have not had any issues, but it is venting (lots of fine dust) from the same room it came from, so there is likely some kind of pressure balance there. If pictures help here say so and I’ll take some.


So, without starting a Hillary vs. Trump discussion (could not resist :-), what would you folks do here? My goal is to get the bad, really fine and invisible stuff out of the house.



As always, thanks for everyone’s feedback!


Regards,
Paul

[John M Wilson]

I think I want a separator before my DC, then a cartridge filter, then send everything else outside.

I'm no expert, but I believe if you have a cartridge filter, you don't have to vent outside.

I'm under the impression that the benefit to venting outside was to avoid the pressure loss and cleaning hassles from the filter.

If you do a cyclone into a good filter (such as Wynn), then you will be catching all of the nasty stuff, and won't have to deal with any of the negative pressure issues.

But that's just my understanding... there are many on this forum who are true, bonafide experts in this stuff.

[Dave Stuve]

Paul, is this a one-time cleanup or is this your new dust collection scheme? If it's one time cleanup I'd be tempted to try and rent a HEPA (or otherwise very good vacuum) and spend a day cleaning everything with a dust mask on, and not worry about pulling CO in from your gas appliances.

[Martin Wasner]

The safe bet is to do a better job filtering the air.

You can open a window. I wouldn't be concerned with anything other than cold air.

[Paul Richard]

Paul, is this a one-time cleanup or is this your new dust collection scheme? If it's one time cleanup I'd be tempted to try and rent a HEPA (or otherwise very good vacuum) and spend a day cleaning everything with a dust mask on, and not worry about pulling CO in from your gas appliances.

This is what I want to set up long term. Its a good thought though that I'd not considered, I probably do need to do a thorough one-time clean up, but for this thread I'm hoping to get feedback on what I've proposed for my setup.

[Doug Garson]

I'm confused by your statement:

"That said I think I want a separator before my DC, then a cartridge filter, then send everything else outside."
Paul

I'd be interested to see how you would configure it.
Not an expert but for your limited shop use, the heat loss would not be a big expense. I would go with a Thien baffle separator, skip the canister filter and vent outside thru one window, bring makeup air thru the other window with a heater and add outside combustion air sources for the furnace and water heater and an ambient air cleaner to clean up the dust that your dust collector misses.

[glenn bradley]

Dad cut a hole in the wall, built a lightweight plastic flap that hangs over it and ducted the top of his bagger out of it. It is just a plywood plenum with a bit of rubber mat used as a gasket where the assembly is bungee'd to the top of the unit where the bag used to go. He doesn't need to worry about venting heat where he lives and it has worked great for him for years. Thanks to living at the end of a small valley that leads to the ocean (near constant sea breeze) there is no sawdust to be seen even after all these years.

[Alan Schaffter]

DO NOT, DO NOT, DO NOT vent outside!!!!!!!!!

The air leaving will cause make-up air to be drawn from the furnace - reverse flow of flu gases containing carbon monoxide!!!!! Carbon Monoxide is a colorless and odorless gas- and it is a KILLER. Google CO and read about it yourself. Just a little CO goes a long way, it bonds easily with your hemoglobin, much easier than oxygen, it prevents oxygen from bonding, CO buildup in your blood is cumulative, and it just doesn't leave. If you live, treatment usually requires you spending many hours in a hyperbaric chamber breathing 100% Oxygen. One furnace can produce enough CO to easily kill you- two will do it for sure, throw in the water heater and no question. First comes a headache, followed by confusion and dizziness, and passing out, in fairly short order- you'll be dead by the time someone finds you. You can't rely on an open window providing all the make-up air.

[Andy Giddings]

+1 on Alan and John's comments. To get rid of the fine dust and stop it from coming back, you need a good catridge. I had a 1 micron bag filter and had the same problem. Switched to a better 0.5 micron pleated filter and little or no dust since. You also have a lot going on with 4 inch pipe on a smallish DC. If you can afford to switch to a 6 inch main duct and only use 4 inch flex where absolutely necessary (last few feet to machine) you'll be in a much better position in terms of suction, especially if you want to add a separator. Static is the least of your worries - see the other thread discussing this http://www.sawmillcreek.org/showthre...-Wood-Magazine. As you're familiar with Bill's website, I would recommend downloading and using his static pressure calc spreadsheet - it will help you to see how much of a pressure hit you'll take from different configurations, especially when it comes to duct diameters, flex vs straight and so on

[Don Parker]

I'm with Alan. Pressurized outside venting, combined with those furnaces and the water heater, is a bad idea.

if you have a self contained shop, without a heat source that will kill you if you monkey with how it gets fresh air and vents harmful gas, and you want to vent outside, that's fine. Have at it.

if, however, your shop shares space with a heat source that can kill you if you monkey with how it gets fresh air and vents harmful gas, your dust collection and filtering system needs to be a closed circuit. It needs to spit out into the shop the same amount of air it sucks in from the shop.

At the very least, hire an HVAC contractor for an hour to give you advice after he/she inspects your shop space. The Internet is probably not the best way to get this critical information about how you should proceed.

The fine dust is the thing to worry about, but very good filters take care of it, once it is sucked up.

The bigger question in a shop like yours is whether you really are capturing the fine dust. If you have read the Bill Pentz stuff, you know that he recommends a heftier system than you currently have, with much more aggressive capture at the tool.

Good luck, and be safe.

[Brian Tymchak]

In lieu of venting outside, I would recommend a better bag or canister but DCs are designed to pick up sawdust at the source. Not so good at very fine dust that tools will throw in to the air. I'm a big fan of multi-level dust collection. I recommend also getting an air filtration unit which is designed to collect the fine dust from the air. I would also recommend some sort of a pressurized mask if you don't have that yet.

[William C Rogers]

I agree venting outside in your shop is a problem because of the makeup air needed. IMO your best solution would be a cyclone with a canister filter. Cyclones do a good job of separating the dust before the filter. Also recommended is a air filtration system. I vent outside, but still have some dust in the shop. I have a makeup air source for my D.C. The main benefit from venting outside is it does is cfm increase and eliminates cleaning a filter. However the amount of dust in the shop would'nt be that much different. You just can't collect everything at the source.

[doug m williams]

How are you thinking of venting outside after the filter anyway? You'd have to catch all the air leaving the filter and vent that. Maybe build a box that surrounds the filter with a port to shunt the exhaust to one of your windows? I don't think I have ever seen a configuration like that.

[James Gunning]

In your case, I totally agree with Alan and the others that strongly caution against venting outside. With an oil furnace and water heater in the same room that you work in, if you vent outside, you have the perfect storm to have carbon monoxide poisoning. A cyclone with a good canister filter, tight-leak free connections, ducting and pickups will almost totally eliminate the dust problem in your shop. It could be a commercial cyclone or one built by you. A thorough cleaning before you start would give you sort of a baseline to see how well the system performs.

The single stage duct collectors with bags are better described as "dust distributors" rather than collectors. They do pick up the chips, but pass the fine dust right on through to settle in your shop and lungs. I used bags at first, then went to a canister filter. When I got tired of cleaning out chips and dust caked in the filter I got the cyclone. Job done. Now I clean the filter once or twice a year, and my shop stays clean. No dust collection system gets every last bit of dust, but a well designed two stage system will catch well over 95% of it.

Here is the portable unit I built using my blower, a Oneida Super Dust Deputy, and a Wynn filter. Yours may not need to be portable and construction and ducting may be easier.

SDD-PS blower-Wynn filter.jpgSDD-PS blower-Wynn Filter-4.jpgSDD-PS blower-Wynn Filter-3.jpgSDD-PS blower-Wynn Filter-5.jpg

As Andy suggested, upgrading your ducting to 6" would be a major improvement. The 4" ducting just doesn't carry enough air to use the full capabilities of the blowers most of us use. A 4" duct carries less than half the airflow a 6" one does. If it's possible at all, upgrade the pickups on your machines to 6" as well. This is always controversial since many machines come standard with 4" ports and some machines will require some surgery to upgrade. I did both, and saw a real improvement in how my system worked.

[paul cottingham]

I vent outside, using a thien "top hat" with a blower mounted on top. My house is heated with a heat pump, (with electric back up) so I have no danger of co2 or flue gases. It works great.