To those of you running a 900+ CFM fan...

[LampworkbyLori]

Is it very loud? Is it going to suck the life out of my torch? I'll be working in an enclosed Barley box-type setup.

Thanks.

[Heather/Ericaceae]

My own fan is only 350ish, (the bare minimum) but I gotta say that 900 sounds like a lot! The trick will be getting enough controlled replacement air so that your house doesn't start sucking air back in through your furnace exhaust, for example (which could potentially kill you with carbon monoxide). I'm not an engineer, but at 900 CFM make sure that you have at least 2 windows (or 1 whole door) open nearby at all times. If you do, then no worries!

What you might want to do is put the fan on a dimmer switch (if it's compatible - again, you may need advice from an electrician) so that you can operate on half-power for normal jobs and boost it to 3/4 or full power for fumier applications like metals or lead-based furnace frits. Fully-enclosed workareas like Barley Boxes generally need less fan-power. Hopefully someone smarter/more experienced than me will jump in with more details! Bottom line: it can work okay if you give it plentiful replacement air, but you might be comfier if you can turn it down for normal work. 900CFM is LOTS! Good luck! -H.

[LampworkbyLori]

Thanks, Heather!

[RSimmons]

I'm using a squirrel cage blower for my exhaust system. I built a plywood box for it as a vacuum plenum and insulated the inside of the box. It pulls well and is reasonably quiet. The make up air is supplied by the 10 inch duct fan (Suncourt) that came with the GlassCraft exhaust hood. My wife works with her beads in the same room where I have my torch and she's happy with the sound level, if that tells you about the noise.

Robert

[LampworkbyLori]

Well..

Based on all of the calculations posted on the relevant forums :-k I decided to go with the 900 CFM fan. Unfortunately, the manufacturer of the fan recommends that you do NOT add a variable control switch. So, we're going to put a damper in the 9" exhaust ducting to allow me to adjust the static pressure.

I should have plenty of make up air coming from the outside up through the bottom of my workstation through an 8" insulated flexible hose.

I guess if the fan is just simply too much I will just switch it out for another. :confused:

I'm hoping my contractor will be able to install everything next week.

This whole ventilation deal has been SUCH a PAIN! ](*,)

[cheeky monkey]

my heating guy installed a furnace blower fan. It has 3 setting options, I think i am on the mid range. He wired a plug onto it, then built an aluminum box around it and used rigid metal ducting to my hood. The ducting that came with the Glasscraft fan is not right, it is flexible and you get too much turbulence. (I did keep the Glasscraft hood though) I do not have a Barley box as I don't think i need one. \\:D/ NOW I get good air flow, it sounds exactly like my furnace when starting up but has not interfered with my music or concentration at all. I love it!!!!

[Heather/Ericaceae]

Bear in mind that increasing static pressure without slowing your fan power will put a lot of extra strain on the fan motor, if I understand previous threads on the topic. And 8" make-up air ducting should be about right for a 350-400ish fan but maybe not for 900... I am not a big expert but I've read a lot of posts by Mike A... ;) I would kind of be leanng towards switching for a 400-500 CFM blower. Your hood and make-up air set-up sounds perfect for that! -Heather

[Beadanna]

I can't think where I came across it but I've read recently that what is advertised as, say, 600 cfm actually only delivers about 300. Something to do with 'free air'. Something to that effect anyway.
Can anyone jump in here with details of this?

[Hayley]

Anna - what you read was on booster fans, those that are supposed to be used with another system to help the air flow. The GlassCraft hood I purchased years ago came with one of those - it was sold as a 675 cfm fan but in fact only did 250 cfm on its own. I replaced it with a 1200 cfm CAN fan.

[Moth]

I have a 1200 cfm attic ventilation fan.

I can put a puff of talcum powder into the air near my face and it sucks it right up the ductwork. It passes the smoke test and the incense test. It is approximately 34 inches above my benchtop and I do have something similar to a barley box but I'm in a corner so my back corner is angled, not flat.

There is a basement window open for replacement air behind me.

I've had no problems with my torch being blown about. I do not think that my 1200 cfm fan is actually drawing 1200 cfm of air. I think some is lost in the turn it has to take to get from my bench to the outside. (The fan is outside) It is only a 5 foot run between my torch and the fan, but still. I think it realistically only pulls about 800 cfm.

Best of luck to you.
~~Mary

[NMLinda]

Lori - Similar to Mary, I chose an inline fan that's about 1200 cfm for my Barley box style vent hood. My opening is about 48" by 28". I could have used a fan around the size you picked, but I ended up needing quite a few bends and some long vent pipe runs to be able to get the exhaust far enough away from my fresh air intake to feel safe. I therefore oversized the fan because of all the static pressure losses I had to account for. My actual cfm at my bench is between 900 cfm and 1000 cfm, which is what I calculated I needed. My torch flame does fine with the draw, by the way.

I decided to be more worried about my lungs than the noise, but my fan did sound a bit like a jumbo jet taking off until I did what Richard did - built an enclosure around it and lined it with insulation. Helped a lot. I've also read here on LE that putting insulation on the vent pipe run from the fan can further reduce the noise, which I haven't yet tried. In the meantime, I use earplugs for further protection, even though the fan now doesn't seem much noiser than a largish bathroom fan.

I wouldn't add a variable control to the line. It can hurt some fan motors if they're not designed for that, but more so, unless you have a way of calibrating the cfm with the position of the knob, you won't know if your cfm is still high enough for the size of your hood. Motor speeds of fans are not necessarily linear with the position on the knob. For similar reasons, it's not a good idea to put a damper in front of your fan - you'd somehow need to calibrate it so that you didn't have your cfms too low, plus you might run the risk of overheating your fan, as Heather indicates.

You're safest picking the size fan you need for the size barley box you want and leaving at the manufacturer's designed speed. If you find the noise bothersome once you get it installed, try Richard's idea of boxing in the fan and insulating it, and also muffling the vent pipe with insulation. If that still isn't enough, try wearing ear plugs.

Hope that helps
Linda

[Beadanna]

Anna - what you read was on booster fans, those that are supposed to be used with another system to help the air flow. The GlassCraft hood I purchased years ago came with one of those - it was sold as a 675 cfm fan but in fact only did 250 cfm on its own. I replaced it with a 1200 cfm CAN fan.

Thanks Hayley!

[Mary K]

I have an 900cfm granger (squirrel cage ) blower fan. Mine is mounted outside my studio in it's own little housing. I am glad it's out there. As for blowing your torch flame around, that would be caused more by your makeup air source placement. My make up or replacement air comes in at the back of my bench and I have 4 eight inch solid pipes. I believe that only one will not be enough. I have little doors that I can open on the outside for my makeup air vents, and I always open 3 of them, and sometimes the fourth one, but that one is just vented to under the table, so it depends on the weather if I open that or not. I also have windows (2) that I can open/crack depending on the weather. I run my airconditioner and I know my fan pulls air from outside thru that, as I must cover it tightly in the winter or get a cold draft thru it. Your make up air must equal your exit air or it will not work.

[NMLinda]

Mounting the fan outside is a great way to reduce the fan noise to almost nothing, for those who have a way to do it. Don't believe it really matters terribly where the fan is along the vent pipe. Another great suggestion for you from Mary K, Lori!

Linda

[cadia]

I have an 800 cfm squirrel ~ it is LOUD!
I did install a damper but the fan force wind kept pulling the damper almost shut (!!) , then the fan wouldn't effectively clean the air, but would reuse the studio air (ugh). Damping it down didn't do much to cut the noise. Someday , soon I hope I will mount it on the outside of the wall, and hope it is quieter. I probably will also try insulating the pipe< I think I am also hearing the fan noise coning down the vent pipe, earplugs won't help, I want to hear the MUSIC!!!
I have a funnel type exhaust, not a BB.

[Hayley]

Sometimes it's not the fan that's loud but the air going through the ducting that makes the noise. When we shortened our ducting by 2.5 feet, we were surprised how much quieter it got.

[Dale M.]

Noise can come from a lot of things when it comes to moving air.... Having fan outside of building will help, having fan motor and assembly mounted on rubber anti-noise/vibration mounts help, having flex joints where duct connects to fan housing helps... Wrapping duct work with noise absorbing insulation helps.....

Dale