Workshop exhaust fans

[Bob in St. Louis]

Hey all,
Curious about an exhaust fan for the workshop.
In my basement workshop, I do a fair amount of wood working, painting, staining, a (very small amount of) metal working, and am thinking about bullet casting down there too.
Today I spray painted a few things in there, which darn near messed up the whole house. The smell of this paint gave me "the look" from the wife.
I'd like to install an exhaust fan (or two?) to help keep the nasty stuff out of the house.

So those are the uses of the shop. It is 12' x 19' x 8.5' tall and in the basement. I've got access to the sill plate area, so I can poke a 4", 5", or 6" hole without a problem. I'd like to know what you guys are using, and the CFM you're talking about.
Thanks in advance fellas.
Bob

[rancher1913]

around here we pick up mary jane grow operation fans, they are in line and quiet. craigslist almost always has a bunch from a remodel. don't know about explosive vapors thru them, might be dicey but an explosion proof fan will set you back a good bit.

[Bob in St. Louis]

I actually google searched that, and was surprised to see actual fans for sale!?!?
But "explosion proof", isn't needed for my operation, nor is the mary jane aspect.
Although, if your area has an excessive amount of them, maybe you'd be so kind as to help me out with a purchase.

Seems the prevalent drug of choice in my area is meth and heroin, so no fans needed, I guess.

[CastingFool]

See if you can pick up a blower and motor taken off an old furnace. they can move a lot of air, and they are relatively easy to mount.

[frkelly74]

I use the fan off the top of an old AC unit that was on the house when we bought it. The system was old and not holding refrigerant but the fan still runs. I took out a window and framed in for the fan and mounted it on the outside. It is 240 volt and will move some air. Kind of noisy though.

[dverna]

The issue is you need make up air. If you live in a cold climate, the air you suck in is cold and will cause a heat load. Same issue if it is hot and you use AC.

If if I was setting up an indoor casting bench, I would look at a fume hood and run two ducts. Exhaust and supply.

Don Verna

[runfiverun]

your room is about 1800 square feet.
anything that moves 100 cfm out would completely clear a volume of whatever in there every 18 minutes. [the throttle body on my mustang would do it in under 2 minutes]
you'd have to make up the hot or cold air in that amount of time.

just the smoke off a casting pot would suck right out, taking about 1/4 the areas heat with it through a 4" pipe with an exhaust fan and a hood [from a kitchen] in about the same time.
don't get too carried away with CFM it's more air than you think.

[Andy]

You can get a brand new 6" centrifugal "in-line" style fan pretty cheap due to all the potheads creating a demand for them for whatever it is they do in their basements/attics. I bought one on ebay for a woodstove heat recirculating thing I did and only realized this once the box came in with a pot leaf as the company logo (great business practice guys), won't be buying from them again.

the fan works great though and a centrifugal fan can push or pull through a lot of ducting without losing as much CFM as a regular in-line blade fan. You can run these fans with a variable speed control for a woodworking router and (as long as you don't turn it down so low it doesn't turn) that works well to reduce the CFM when you want it lower.

So, you could buy one of these setups, pipe it out your sill area and make a hood for it over the table you want to spray finish and cast on. The CFM you want for removing spray is much higher than what you need for lead fumes so the adjustable nature of this option gives you a good compromise solution. You're probably looking at about $150-200 to do this correctly depending on the deals you find.

[shredder]

[the throttle body on my mustang would do it in under 2 minutes]

I would love to drive your mustang!!

[Handloader109]

I have two blower fans on my wood fireplace that circulate air. Each has simple control that is in reality a light dimmer. Works fine. Id go to your local hvac installer and see if they have or would hold you a used blower from a dismantled/replaced unit. Maybe $20$30 tops. Maybe even free, control is about $10-15 make sure it can be used for induction use. Orange or Blue stores have them. Build hood, and turn low for casting, just want to take fumes out. Lacquer will require high speed! If you need makup air, small vent could be installed. I use a 200 cfm blower for my laser exhaust and makeup is needed every now and then. I can pull smoke back in from an unused stove in the basement that has its chimney next to main fireplace. Only happens in no wind and high humidity, but i do watch for it.

[Hickory]

Here are some ideas.

https://www.amazon.com/s/?ie=UTF8&keywords=thru+the+wall+exhaust+fan&tag=mh0b-20&index=aps&hvadid=14303854803&hvqmt=e&hvbmt=be&hvdev=t&ref=pd_sl_44ja13qwzb_e

[rancher1913]

if you find one let me know, I can pick up and ship if needed.

[castalott]

But if you run hot exhaust gases ( think smoke from fluxing and such) thru a fan with plastic bearings ( yes, some are) , the bearings will melt and the fan will go 'kaput'. Ask me how I know this.... I suggest a better way is not run any exhaust gas or heat thru any bearing or motor... keep the bearings and motor outside the air flow.

Dale

[lightman]

I have a 36 inch fan built into the gable end of my shop with louvers that open when I start the fan. I think its 1/3 hp. It will suck out the smoke from my welder or when I'm smelting dirty wheelweights. These are not terribly expensive but do require some work to install. I also have a 48 inch fan that I can roll around that moves probably even more air. Depending on the quality, they run from $200 to over $500. My shop is only heated with a portable heater and has no A/C, so thats not a problem.

[Bob in St. Louis]

Great ideas fellas, thank you. This is giving me some food for thought. I hadn't thought about adjustability for various needs either, I was thinking about a simple 'on' type fan. Great idea. Good information, thank you all. Looks like I've got some shopping to do!

[Echo]

I surely like the idea of intake and outlet vents. Maybe run a piece of dryer hose from the intake vent toward your work bench, with the fan sucking from above and blowing out the outlet - maybe?

[Bob in St. Louis]

What might be a good idea.....
Have two fans.
If I don't need much CFM, have one as "intake", and one as "exhaust" in the workshop. This would mean the shop is self contained, and separate from the rest of the house.
In the case where I need A LOT of CFM, have them both as "exhaust", and use a window elsewhere in the house as the intake. This would then require the rest of the house be part of the equation, as it would have to supply the "intake" part.
That would ensure none of the "nasties" would enter the rest of the living space.
That make sense?
Thoughts on that?

[higgins]

I don't have an exhaust fan, but if I decided to install one, I would contact the local remodeling contractors and see if they have a range hood they've taken out because it's the wrong color, wrong metal, or just looks "dated".

[Geezer in NH]

:groner:
I would love to drive your mustang!!

[Bob in St. Louis]

I thank you fellas for all the advice. Here's what I ended up buying.
Since we all like a good pictures of a workshop, I'll be sure to take a photo or two of the final product installed.
Thanks again!

https://www.amazon.com/gp/product/B01CISRESC/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1

[Grmps]

This is cheaper and will do the same thing
https://www.amazon.com/TerraBloom-Inline-Booster-Exhaust-Ventilation/dp/B00WW4H8XY/ref=sr_1_2?ie=UTF8&qid=1486506322&sr=8-2&keywords=6+inch+inline+fan

larger diameter makes higher volume easier / cheaper the only thing is you have a bigger hole to drill/cut

you don't really need an intake fan But you could use it in conjunction with the exhaust fan to build pressure in the room and improve the exhaust fans capacity you should have them on opposite side of your work shop), just run a 6 inch intake pipe down to the floor (make sure you put hoods and screens on them to keep the rain and critters out). make sure the basement is sealed off from the house and try to get the exhaust fan drawing from the highest point to get all the fumes or contain an area with plastic and vent out of there.
You could put a Y in the 6 inch pipe leading to the exhaust fan allowing you to vent from the high point in the room, your casting area or both.
With that big of an exhaust fan you may want to put a rheostat on it so you can control suction. Most of the time you will need very little right over your casting pot.

[Bob in St. Louis]

Thank you!
I saw those, but the entire unit looked like a noise factory. While it may be quiet now, it just screams (pun intended) I'M GOING TO RATTLE.
Well, I'm pretty OCD about noises that don't belong, and wanted something that was quiet. The reviews said it was quiet, but they didn't say if it was quiet a year from now. So I spent the extra cash, and got a design that looks like it has silence in mind.
The one I chose is 52dB, which is pretty quiet. Those galvanized units didn't have a dB rating.

I do very much like your idea of a 'Y' and pull from two locations. Being a long room, I'm thinking about mounting the fan in the center, and having the intakes at opposite ends. One end I could cap off, and bring down to the casting hood. I've got a 4" dust collection system I'm installing for the woodworking tools, so the use of blastgates isn't lost on me.

[Bob in St. Louis]

Well, I've purchased everything I need, and noticed right off the bat, that the "four inch fan" I bought has an inlet and outlet size of 3.75".
Based on recommendations here, >> THIS << (https://www.amazon.com/gp/product/B01CISRESC/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1) is the type I bought. Am I missing something here? There's a HUGE gap between this and the inside diameter of 4" PCV pipe.
Thanks!

[runfiverun]

the 4th picture down on the left say's it's 4"OD.
you should be able to use some flexible dryer vent and clamp it in place.

[jsizemore]

Well, I've purchased everything I need, and noticed right off the bat, that the "four inch fan" I bought has an inlet and outlet size of 3.75".
Based on recommendations here, >> THIS << (https://www.amazon.com/gp/product/B01CISRESC/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1) is the type I bought. Am I missing something here? There's a HUGE gap between this and the inside diameter of 4" PCV pipe.
Thanks!

How does it match up to 4" steel duct pipe? From personal experience, you rather it's .25" too small then .25" too big!

[blackthorn]

This calls for a "Red Green" solution! LOL

[Bob in St. Louis]

Whoever measured this and said it's 4" OD, should be smacked in the head and have their measuring rights taken away from them.
The ID of 4" PVC is exactly 4", and this fan fits as tight in the pipe as a 9mm boolit fits in a 12 gauge.

Not sure on the 4" steel duct, I don't have any on hand. The pieces I have, have been cut up for other projects and lost one end.

"Red Green" solution?.... I'm all ears!

Just so y'all know I'm not smokin' the funny stuff, you can check my math:

http://i85.photobucket.com/albums/k60/BobinStLouis/House/Workshop%20Remodel%202013/DSC_0098_zpst7jtwyiw.jpg (http://s85.photobucket.com/user/BobinStLouis/media/House/Workshop%20Remodel%202013/DSC_0098_zpst7jtwyiw.jpg.html)

[kmrra]

Just installed my hood today in my casting room im working on 188380

[RogerDat]

Bring air in at the bench and exhaust above the bench. Along the line of vent hood on right then put an vent inlet left of center. While you will draw some house heated/cooled air out the exhaust you will have ability to get major portion of the air flow from the nearby inlet. One smart move is to have the larger CFM at the exhaust side, variable on the inlet so that you can dial it down and create the negative pressure toward the basement mentioned earlier. Really helps suck fumes away from the sensitive nose of dear wife.

Not trying to avoid any house air getting pulled out just limit it so you don't dump your heat or AC

[Bob in St. Louis]

Good words Roger, thank you.

In the meantime, I'll continue to scratch my head regarding how to attach a 4" pipe to the in(and)out of a 3.75" pipe.
I've got a few "rigs" in mind, but.... well.... I shouldn't have to rig this, right?

[GrayTech]

A strip of ½" thick foam glued in the PVC pipe will make a great seal and stay easily removble.

[retread]

The issue is you need make up air. If you live in a cold climate, the air you suck in is cold and will cause a heat load. Same issue if it is hot and you use AC.

If if I was setting up an indoor casting bench, I would look at a fume hood and run two ducts. Exhaust and supply.

Don Verna

I'm with Don Verna on this one. I use a fan off HVAC unit and exhausted it out a window right at my reloading bench. No problem until one winter day I had the Airtight wood stove going and forgot to open another window for incoming air. I was busy casting and after a bit I smelled smoke. I looked back in the other end of my shop where the woodstove was and that end was filled with smoke and heading my way. Without another source for incoming air it was sucking the air out of the stove intake. Haven't made that mistake again.

[Whiterabbit]

Sucking air out + wood stove = carbon monoxide in the house.

Anyways, assuming OP heats via electric, not gas or wood, your cheapest solution by for is to cruise craigslist for a good dust collector. You can get one for $150 or so that will do double duty as dust collection, suck at a rate of 1000+ CFM, pull airborne particles in the 5 micron range if you buy cheap, 2 micron if you buy good, and 1 micron if you buy REALLY good. I'd say a must have if you gas weld or stick weld down there. Or cast. Or woodwork. Or smoke cigars :)

But I don't live in a cold climate, so I don't have to worry about heat load, really.

[blackthorn]

Old "Red Green" would have wrapped it with something and held it all together with duct-tape! Or maybe just wrapped it with tape. LOL

[Bob in St. Louis]

A strip of ½" thick foam glued in the PVC pipe will make a great seal and stay easily removble.
I think you're correct.
I've got a bunch of memory foam here. Might be possible to make a big fat round gasket for either side of the fan.
The one thing that can't happen is for the intake gasket to get sucked into the blades. This fan looks like it has a near zero clearance between the blades and outer case, so a large wad of foam getting sucked in might be catastrophic.
It still baffles me how they figure that's four inches.

My house is all electric, so no worries of CO. Good thinking though, thanks fellas!

[jsizemore]

You might try getting some rubber or vinyl hose to make a gasket for the end of the PVC pipe. A piece about 12.625" long should take care of each side. Split it length wise so it will fit over the edge of the PVC and wont slip off. Some #8 x 1" self piercing screws driven through the PVC into the fan mounting flange should keep everything snug and air tight.

[Bob in St. Louis]

That might just be the winner, right there.
Thank you!

[jsizemore]

3/8" ID hose would probably be the easiest. Split down 1 side and fit for length. Slipped on the edge of the PVC pipe it should stay with no adhesive. Good Luck.

[jsizemore]

This is the exhaust fan I use:

http://www.ebay.com/itm/Jenn-Air-Down-Draft-Blower-Assembly-/162402026847?hash=item25cfea455f:g:TN4AAOSwr~lYqkQ S

2 speed fan. 450/200 cfm. It can be mounted remotely and will still suck flame from the top of the lead pot 12" away. 6" intake and 5" exhaust which I've adapted to 6" with a wall exhaust hood for gas logs.

I grabbed mine from a range that was scrapped at the scrapyard. All the other parts and pieces I got at Lowe's.

[MT Gianni]

For the average age of the forum if you remember opening a can of soda or beer with a church key you needed two holes, one for the drink and one for air. The rule of thumb to balance an outgoing fan is 1.1 x the outlet air, in other words if you have a 100 square " moving air out you need to replace 110. The air will come from somewhere if you don't with potentially hazardous results if it is a chimney vent.

[Bob in St. Louis]

3/8" ID hose would probably be the easiest. Split down 1 side and fit for length. Slipped on the edge of the PVC pipe it should stay with no adhesive. Good Luck.
Yes indeed, I think you're correct. Thank you. I'll letcha know!

[Bob in St. Louis]

Thank you Gianni, I'm all electric, so I'm safe in that respect. Thanks!