Ventilation system

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Hi All, just came over from the Hobart site. I thought I would post a few of the projects that I have posted there. This forst one is a ventilation system i installed in my shop. Attached Images
Reply:Hey Scott don't raise up and hit your head on that sheetmetal duct. Just concerned for your health. DavidDavid
Reply:Echo, Thanks for the concern, thats one of the reasons I put the flex duct on th end. I can raise or lower it as needed. It is not as easy to hit your head as it may look. The table is 3'x4' and it is centered on the table, so it is really out of the noggin zone
Reply:Scott, great looking vent system, is it strong enough to take the smoke and fumes away as you weld, or does your room still fill with smoke and fumes? and your Ventilation system just vent your work space faster?Thanks
Reply:Dave, It works great. You can watch the smoke get sucked right up. It pulls 600 cuft/min. The duct run is under 6' with only two bends.
Reply:Scott, I got two blowers today.  One 120V and one 230V.  The 230V came off of a central air system.  Too much, I think.  What did you do for the exterior wall where it vents?  If you posted on the old site, I probably missed it.mow
Reply:Mow,I took a piece of sheetmetal, cut it the size of the sliding basement window. I cut the hole for the duct and welded it to the sheetmetal. I can still open and close the window. So when I am done, I just slide the window shut.
Reply:Ok Scott, I'll have to do something different.  I'll probably just get a louver of some sort for it.  Thanks for the pictures and the info.mow
Reply:Mow, I am not sure what your particular application is, but if you need to go directly out through a wall, you can buy a sheetmetal vent. It looks like a larger version of a dryer vent. It has a flap on it so when the blower is off, it will close. I hope that helps.
Reply:Thanks, Scott.  That would be perfect for what I need.  I'll start looking for one.  I hope that it won't be hard to find.  mow
Reply:Mow,Try a good appliance dealer. They should carry them for down draft stoves and commercial range hoods.
Reply:try filtering it with a good media and maybe some charcoal- takes the stink out and the keeps your exterior walls from going black- which in turn keeps the neihbors happyKeep your stick on the ice
Reply:Filtration doesn't need to get as exotic a s charcoal to be effective.  A simple "grease filter" of the type used in a resturant hood sprayed with corn oil will capture over 90% of airborn particles.  The remaining 10% is very expensive to capture.The problem with filtration is the requirement to compensate for the restriction it puts in the air stream.Appreciation Gains You Recognition-
Reply:Thanks Scott for all the information
Reply:You are very welcome, Dave.
Reply:Talking about filtration, Is that really necesary? Would the system be damaged? or is it to keep the fumes from blackening the wall?Scott, Do you put any filtration system in yours? Where did you find the retractil black duct? Why did you put the blower close to the window with a longer intake duct, instead of putting it close to the welding table with a longer exhaust duct?I am on the verge of making mine I need to consider all the details.Alfredo
Reply:AmalgamI have no filtration on it. Don't see ant need, it is venting to the outside, not near antthing that can be affected by it.All the parts I recycled from my old jenn-air down-draft stove.The reason for the location is the intake is 6" and the exhaust is 5" on that blower, so I wanted the longer run to be the larger diameter. I hope that helps.
Reply:So how do you let air in?  If you are pulling 600 cfm out do you just open another window to let air in?
Reply:Scott,Can you and the boys smoke a cigar by that without your wife complaning?
Reply:Rule #1, You can only remove the amount of air from a room that you replace into the room.Rule #2, most rooms leak like a sive, that's why your heating bills are so high.Now, if you want to be really technical, since that air you're sucking out is hot, the cubic feet of cold replacement air you need are less.For most welding shops, makeup air isn't a problem cause a door or window is usually open anyhow.The problem shows up for a guy with his shop in his garage, or cellar who also has a gas water heater and furnace in the same room.  If makeup air isn't provided to the welding area, it will find its own way in, and the path of least resistance will be via the flue from the gas appliance.  That might be fine, if the gas appliance isn't burning, BUT, if the furnace is on, since you are using the flue for a fresh air intake, the products of combustion will become part of the makeup air stream, due to the design of the furnack or other gas appliance.When you look at a resturant type hood, you'll notice there is a fresh air supply duct coming into the hood to prevent just this problem.  There is an exact formula for the size of makeup air you need for any exhaust duct, but I don't remember it.Where you source the makeup air should be as far from the exhaust air as possible, or at least 12 feet above the exhaust air to minimize nasty stuff in the exhaust stream from being drawn back into the makeup air.Other things need to be considered in makeup air systems too, like BUGS & small critters.For a small shop, like a garage, you can just leave the garage door up a couple inches, and exhaust out the back of the garage.You can also install a drier vent cap on the opposite wall of the shop and remove the damper.  Stuff a sponge or rags into the makeup air duct when not in use, to shut off the air stream when the exhaust isn't in use, or if you have lots of cash, you can equip the makeup air duct with a shutoff like woodworkers use on dust collectors.Appreciation Gains You Recognition-
Reply:Originally posted by Sticky Scott,Can you and the boys smoke a cigar by that without your wife complaning?
Reply:I have another window like the one you see in the pic on the opposite side of the room.
Reply:Originally posted by Franz Right wife and you don't even need an exhauster when you smoke a cigar.
Reply:I have too many bad habits, thank God, smoking is not one of them. My first wife died from a lung disease( Cystic Fibrosis) when we were 23. My mother died at age 42 from smoking.   That could be the reason I hooked that vent system up in the first place.
Reply:Sorry to barge in guys,I am an HVAC tech and would advise 8"duct to acheive 600 cfm exhaust.The way that is you will have 400 at best.Also louvers can be bought at home depot or if you have a sheetmetal fabicator nearby they should be able to help you.They will also have access to 8"flex.Good plan on the fume extractor though.I built many for the railway welding shops here with cyclones in the corners and 4"flex attached to the welers sleeve it worked awsome.Nobody moves nobody gets hurt(safety first)millematic passportmiller 375 plasmacutterScott,  What kind of fan did you use?  Is that a Dayton unit?  I am trying to source a fan right now to build a similar setup and am curious as to what others ended up using?Thanks