exhaust fan/air cleaner location?

T

tradhunter

Joined
Jul 27, 2009
Messages
32
Hey guys, need some advice.

Backstory: I am hobbyist with a small basement shop. Obviously this is not an ideal place to make knives, but for the time being, it is all I have. I do not grind handle materials inside on my 2x72 (only with files, rasps, etc.. , I have a large HEPA air cleaner with furnace prefilter to clean air, and I clean up religiously (proper ppe gear always used) with HEPA Vac, water bucket under grinder..etc. Even with the HEPA cleaner, I have been worried about those super fine particles that even the HEPA doesn't collect and would never be collected or leave the shop (at least in the right way). I already had an extra 6 inch outlet that was originally an air intake for a wood burning fireplace and now no longer in use. I purchased a 12" dustproof 1500 CFM exhaust fan and I plan to use this as the solution in cleaning the air of the super fine airborne particles by venting outside from said outlet. The problem is the outlet itself is probably 15 ft. from my grinder.

Question: What would be more effective cleaning the air/be the best performing setup. Putting the fan close to the outlet itself, so it only had to push the air a few feet before it was through the wall? Even though this would be 15 ft. from the grinder? Or duct over 15ft to the grinder and put exhaust fan overhead of grinder itself? 1500 CFM is pretty strong, but I want to insure there is good air flow all the way to outlet and not leaving particles in ductwork. Shop room is approximately 8' x 18' or so. Can't move grinder closer to outlet.

Thanks for entertaining my strange question.
 
The best way is for you to get an A/C outlet and hook it up to your fan through some flex hose so its about 12" from your dust generation. You want enough suction to try to suck a paper towel down, say about 100 fps velocity. That just below noisy, say windy.

This way all the dust generated is sucked down and blown away. You could put a filter on the exhaust to be nice to mother nature.

Larry
Tinkerer
 
I don't know if every setup is different as I've only set up two matching dust systems in my shops... but the fans I have (some off brand) seemed to like to suck instead of blow... In other words, more ducting in front of the fan and less behind it.

Here is as HEPA was explained to me in hazmat school... HEPA means a rating of 99.9% of like .25-.3 micron particles... But, due to mass and size, that is the size that is hardest to filter. Contrary to intuitive thinking, HEPA filters actually filter smaller particle sizes than that at an even better rate... (99.99% or something...) The bigger particles are also filtered at an even better rate. The smallest particles don't have the mass needed to generate enough kinetic energy to pass through the filter without sticking to media at some point. So, right or wrong, HEPA rating is about as good as you'll ever get or need. Of course for VOC's and the like activated charcoal is needed but at the levels we see a decent mask and proper ventilation is adequate...

One sticking point I have seen some in home built paintbooths mostly... If air is leaving the shop, it has to enter it too. Better that it is managed and clean air coming in...

And like Larry said, just a little windy. Don't need hurricane katrina in your shop sucking up everything you drop... lol.

-Eric
 
1500CFM is a large shop size exhaust fan! It requires a far larger port than a 6" pipe. It also will require a larger air in than air out port to prevent negative air pressure.
Either make some new openings ( 24X12 in and 12X12 out) from the basement to the outside, or change that fan to a much smaller unit. You still will need an air-in port.

A 12X16X8 foot shop would turn the entire air over every minute at 1500CFM. While static pressure would drop that a lot, it would require a 1/4HP or bigger motor to run a fan at that capacity.
 
Thanks for the info guys. Yeah I thought about it possibly being to much power, but I really wanted the little nastys gone. I thought it would need some gusto to push the air out once it got past the fan. I get my air in from cracking the door enough to allow positive flow from the rest of the basement, which has a window I crack too. I wish I could have an air inlet in the shop area, but I would have to cut another inlet in the brick (I curse you big city living). Here are some pics so you can better visualize where I was going with this.

10245326_10104866847675064_4802900400665583826_n.jpg


10274258_10104866847759894_5931018384187455661_n.jpg
 
Get some flexible duct and run it to the window. Let that be the Air In. Hook the fan to existing exit port. That will be the Air Out.
 
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