ventilation installed but nothing but problems
 

installed my hood with the 650 cmf fan, the company supplied a ten inch flex pipe but do to my set up , i had to reduce it to 8". the pipe runs maybe 2 feet and is vented outside through a 8 in vent with baffle, this is a dead straight shot to the out side. turn on my fan, light a smoke and i watch the smoke curl up and over the hood. light a roll of paper and blow it out holding it at the torch head, the smoke comes straight back and into my face. holy smokes, should have stuck with a dust collector motor and a 6" pipe or a box fan at a window, From the moment i preassembled this unit, i had my doubts. baffle flange that one has to assemble to the unit, shows air light every where, the motor flanges are not tight(tape them?). so here i sit $400 in the hole, and what to do, SOB, really had hope this was a done deal, but now I have got to start all over and oh ya got a nice 8" hole out the side of my shop wall. Any suggestions?

Photos? Especially the mounted motor.
And make-up air -- where from?
Me

I'm not sure but I did read somewhere that the pipe going out side needs to up above roof top.
Do you have enough makeup air?

the work bench sits in a four bay garage, 14' ceilings, i've read some post that claim the pull from the fan is so great that it will close doors? no suck luck here, i opened the furthest bay and the air flow doesn't change a bit. in reading the fine print this is 650cfm fan when installed draws 450cmf. forget that, back it goes, i"m shocked it doesn't state that on there web page. hope it is ok to post a link? this is the same set up i have, lees a 8" reducer and a exterior vent that provides 6" of pipe that connects to that reducer. http://glasscraftinc.com/product/pro...m?part_id=7157

ME TOO!!!
 

I know who you bought this from because I got one too. It doesn't say anything on the website about the once installed it's less cfm's..Fraud maybe!!! I do fuming and alot of silver so I guess I'm no better than I was. I called the company after having it installed that the suction wasn't much and she said it was because my back wasn't to the open door in the garage and to put metal sheets on the sides to help collect the air...Yeah, after spending $400.00 and then I won't say how much to have it installed. The dude who installed it didn't think much of it right away. We also now have 2 holes in our garage wall. Husband is pretty happy w/ that. Hopefully no one else will get one from there. I got it because someone on here had one and said it was fine. It also has the fan on the side and not on top...big clue....maybe will call them again..probably been to long...YIKES

well I will let you know how it turns out for me, i don't see it as a problem in returning it, just got it a few days ago, wish i had seen the 450cmf statement, but for $400 plus i think i could find something far cheaper and have lots of money to spend on glass

Murf.get your money back,go to a hydroponics store or look on line in one and get a vortex,they are awesome and will cost less money.
Mary

Reducing the vent pipe from 10" to 8", essentially makes it a funnel, and results in a 33% surface area reduction... and thus significantly reduces the air flow. There may be other installation problems contributing to the lack of flow.

Contact the seller and have them talk you through the installation.

Me

p.s. A 450 CFM fan can flow enough air to exchange 100% of the air volume in a 20' x 40' x 14' ceiling studio -- in less than 25 minutes -- if the vent piping is properly sized.

Here are the issues that are causing this system to not work, besides the CFM issue:

1. Get rid of the flex ducting. Don't use it, don't even think of using it. You are reducing your air flow by between 30 and 50% just from the turbulence the flex folds cause.

2. The duct absolutely has to be the same diameter all the way through the system. Reducing the size of the duct from 10" to 8" reduces the duct area by slightly more than 28" square inches. This causes huge amounts of back pressure.

The fan can be located anywhere on a hood - provided there is a way to distribute the suction evenly over the width of the hood.

If you are using the Glasscraft hood, and the fan actually draws 450 CFM (can you provide some documentation to that effect?) then the fan is way too small for the size of the hood. That hood requires at a minimum 650 CFM, and 750 CFM would be better.

Not to hijack but I have a question.

Do fans usually say on them how many cfm's the move? I've seen some that do but my exhaust had other information but not that.

I was just curious.

Oh, and is it ok for the duct work to be smaller and get bigger at the fan? I thought I'd seen that before. Again, mostly curious.

I have this hood and fan and it does work. I use 10" smooth ducting and I have a 12" makeup air duct behind me. I also have baffles. I have tested my system with an actual nitrogen dioxide detector and I do not get ANY reading of nitrogen dioxide when working. I also tested it without the fan running and the alarm was going off after 10 minutes.

Nancy -- it depends on the manufacturer of the blower/fan. Some manufacturers do, some don't. If it's not marked, never take the word of the supplier but look up the model number with the original manufacturer.

As far as your question about duct work sizing - are you asking if it is ok to (for example) run 8" to the fan, then after the fan run 10"? The quick and dirty answer is yes. You can always INCREASE the size of the ducting in the direction of the airflow, but you should never DECREASE the size of the ducting in the direction of the air flow. (caps for emphasis).

I have to agree with bhhco and Mike... There is something seriously wrong with the way installation is done... Even a 450 cfm fan with hood this size should pull at the smoke from test out of room even if fan is below desired performance...

Have to believe there is problem either with fan itself or ducting , time to reevaluate installation process... Maybe fan is defective and not really pulling air (loose blade) but just making noise.....

Looking at picture (real close) leads me to believe it is blade type fan, which is not very effective at moving air (for hood ventilation) especially when you are trying to force air into reduced duct size... Your HVAC guy should have know this....

Dale

the documentation on the 650cfm fan is in the paper packed with the hood
the top reads and this under the companies heading.

Portable exhaust hood- Cat#30025
hood dimensions-40" long x 24" deep/ship wt. 41 lbs.
CFM Rating with 8' of 10" flex duct- 430CFM installed
the 430 CFM installed in black bold lettering

i knew the reducing would be a small problem or so i thought, i have not used the supplied flex pipe, just a reducer and a foot of pipe or so to the outside.
i contacted the company, packing it up today for a refund less shipping and insurance. i need to figure out a better solution, my having to reduce a pipe or to go with a 8" pipe is a must. there has to be something out there that will work for me, just have to slow down and find it.
I'm glad it works for some, and sorry it hasn't for others. hated to post the link, but my digital camera is in Canada with my daughter right know. I'm not trying to bad mouth the company, let me just state that.
thanks all for the input.
Bayard

Would appear that they are admitting a reduced efficiency when used with 8 ft. of 10 inch flex duct.....

Dale

true Dale, just be nice if that was posted on the net before one orders it. Had I known the purchase wouldn't have been made.
Bayard

Thanks Mike.

I want to purchase (or lease) a NO sensor system (and calibration service). I recognize the expense involved.

What make & model NO/NO2 detector did you use?

Me

Murf i just installed my ventalation and I used the 2 squirrel fans that were used to vent (or run the air conditioner I am not sure they were in a box with another cooling unit under the seat) i almost threw them away the travel trailer I am turning into my studio They were attached to the infloor air conditioner the suction is so good it holds foam board up to the hood when turned on. If you look in a junkyard for rvs or a used parts house you should be able to get one pretty cheap i just ran 2 duct tubes from eithar side of the blowers to a homemade hood and then vented off the back of the box it was in to a window in the trailer. the whole thing cost me 40 bucks maybe and being a single mom every penny counts, a local guy who teaches and has his own studio told me it would be good for any kind of torch it was really too strong for me with my hot head now :) If I can I will get a shot of it tomorrow on the camera I saw some other fans and stuff on ebay that you could make your own and on artglass answers there is a thread on how to build your own hood or torch cabinet Good Luck :)