creekbeater Posted February 13, 2012 Report Share Posted February 13, 2012 I finally decided to set up a workshop in my basement to pour soft plastics. I read a number of posts on this site and others about the requirements to vent the fumes when pouring soft plastics. I started with a kitchen fume hood as I've seen many people use after a neighbor was doing a kitchen remodel. After reading a number of conflicting posts, searching the web, calculating serveral different measures for CFM, including considerations on duct lenght/width, static pressure etc, I learned about the limitations of the kitchen hood set up and decided to build my own custom hood based on designs I've seen. Below is a picture of the current state of my project, a 36" x24" x 6" fume hood,. The bottom of the hood is 24" off the surface of the bench with 8" duct pipe converting to 6" after an 8" in-line duct fan (500 cfm) I found at Lowes for $32. The 500 cfm turned out to be a bust as it was designed to move air in a vent at 0 static pressure and doesn't pull the air up any better than the kitchen hood I started with. I'm looking for a fan that pulls around 500 cfm but I'm not sure what kind of fan is needed fo finish the project. I believe a squirrel cage type fan may be the right way to go. The hood space is 36" x 24" x 24" and I would like to consider using without sides, just the sheet metal in the back if posisble. any recommendations on what type of fan to get and where? I'd like to get one for around $100 if possible. Here is another photo showing the underside of the hood. Quote Link to comment Share on other sites More sharing options...
Kajan Posted February 13, 2012 Report Share Posted February 13, 2012 Looks nice, but you should of went with larger dia pipe and larger fan. Quote Link to comment Share on other sites More sharing options...
creekbeater Posted February 13, 2012 Author Report Share Posted February 13, 2012 (edited) Thanks Kajan. Any reco on the pipe diameter or fan? I wanted to keep the end of the pipe to 6 inch to limit the size of the hole I cut into the rafter as the pipe exits the house. Also the availbe outside vents only went to six inch. Edited February 13, 2012 by creekbeater Quote Link to comment Share on other sites More sharing options...
smallmouthaholic Posted February 13, 2012 Report Share Posted February 13, 2012 Mike - This will do the job but requires a 10" exhaust duct. Then you 'll need a roof mounted exhaust stack for 10" diameter duct. Close in the two sides of your booth if you want it to pull fumes properly http://www.grainger.com/Grainger/BROAN-Exhaust-Fan-5C057?Pid=search Quote Link to comment Share on other sites More sharing options...
mark poulson Posted February 13, 2012 Report Share Posted February 13, 2012 Just make sure whichever fan you pick is explosion proof. Kitchen hood fans are, to prevent grease fires, but others may not be. Don't put a fan in that isn't explosion proof, or you're courting disaster. Quote Link to comment Share on other sites More sharing options...
creekbeater Posted February 14, 2012 Author Report Share Posted February 14, 2012 Thanks Al. I appreciate the feedback and the recommendation on the fan. I definetly hear you on closing the sides of the hood to get the most out of the unit and ensure that no toxic vapors escape. the 10" pipe to the roof is not going to be an option for me and I'm going to have to find something else to work. The rise from the top of the hood is 3' and the horizontal distance to wall and side of house through the rafters is about 6 feet. Is there any reason that I can't vent out through the wall/rafter vs. go to the roof? Would the side vent option requier a different type of fan. One other thing I read is that you will need to return air to the area for the air that is vented out. Is this something you do. Look forward to seeing you a Calvery again this year. Mike Quote Link to comment Share on other sites More sharing options...
smallmouthaholic Posted February 14, 2012 Report Share Posted February 14, 2012 (edited) Thanks Al. I appreciate the feedback and the recommendation on the fan. I definetly hear you on closing the sides of the hood to get the most out of the unit and ensure that no toxic vapors escape. the 10" pipe to the roof is not going to be an option for me and I'm going to have to find something else to work. The rise from the top of the hood is 3' and the horizontal distance to wall and side of house through the rafters is about 6 feet. Is there any reason that I can't vent out through the wall/rafter vs. go to the roof? Would the side vent option requier a different type of fan. One other thing I read is that you will need to return air to the area for the air that is vented out. Is this something you do. Look forward to seeing you a Calvery again this year. Mike You'll have to use an expensive section of 10" flexible duct (Grainger carries it ) Not sure on the side of the building exhaust- google it and see if an appropriate one is available. Not everyone carries 10" vents. Edited to add-here ya go Mike- http://stores.hvacexpress.com/-strse-Z.-Products-by-Size-cln-10-Inch/Categories.bok?_kk=c14c19c2-6b75-4677-b72f-6d279f687afb&_kt=4377943475&gclid=CMDByIO3nK4CFULd4AodVX5qew Edited February 14, 2012 by smallmouthaholic Quote Link to comment Share on other sites More sharing options...
creekbeater Posted February 14, 2012 Author Report Share Posted February 14, 2012 Thanks again Al. so this is what it's like on the "dark side" of pouring plastics. I have a few decsions to make, including considering cutting my losses now before I get in too deep! LOL. Mike Quote Link to comment Share on other sites More sharing options...
bass100 Posted February 14, 2012 Report Share Posted February 14, 2012 A squirrel cage fan will be plenty. That is what I use and it is bigger than the one that supplies heat to my 3 bedroom house. If you buy one new it will cost you a couple hundred but if you go to your local HVAC contractor you can get a used one for about $25. The nice thing about this fan is that when you expand you can keep pulling extra lines off of the fan and still have plenty of suction. I have 5 lines coming off of one fan and if you get your head to close to one of the suction lines it will pull the hat off of your head. I also have extra lines that come down and attach on to the motors on my presto pots, I don't mean over them I mean on them. I take the fan blade off of the motor and attach a metal coffee can to a 4" flexhose and it slips right over the motor. The motors on the presto pots have a thermal cut off switch on them and if they get to hot they will shut off. It keeps the motor plenty cool and there is no fumes at all and there is still plenty of room for injectors to go in. I average 8 to 12 hours a day 6 days a week pouring and my motors never cut off. I also do not have a hood at all. All of my suction is coming from flex lines hanging down over a 12 foot length of bench. I can pull a line down to whatever height I want off of my bench and point it in any direction I want. That way I am not confined to a hood or a small area. Quote Link to comment Share on other sites More sharing options...
mark poulson Posted February 14, 2012 Report Share Posted February 14, 2012 bass100, It sounds like you have a great setup. Any chance you could post some pictures? Quote Link to comment Share on other sites More sharing options...
bass100 Posted February 14, 2012 Report Share Posted February 14, 2012 Sorry Mark, no pics. Almost all of my equipment from the plastics side, lead side, and painting side is all custom built by me. All my equipment is my secret to how one guy can do the job of 3 guys. But I will say the ventilation was the easiest of them all. Quote Link to comment Share on other sites More sharing options...
ROWINGADUBAY Posted February 14, 2012 Report Share Posted February 14, 2012 What about adding two more six inch pipes? Quote Link to comment Share on other sites More sharing options...
creekbeater Posted February 14, 2012 Author Report Share Posted February 14, 2012 Bass 100. Thanks for the info. I'll have to call around to see if I can find a fan on the cheap. Your set up sounds impressive. What kind of vent pipe do you run post fan? Do you vent out a wall or run it to the roof? Quote Link to comment Share on other sites More sharing options...
FishAction Posted February 14, 2012 Report Share Posted February 14, 2012 It's not always the size of the pipe but the volume pulled through. I use a sealed fan driven by a 3/4hp motor that was designed for pulling sawdust for woodworking shops. It has pipe in and out outlets built into the fan housing and moves 450 cfm through a 4" pipe providing enough volume to easily vent out a 160 lb furnace plus plastic pouring. Pipe at several stations is capped off when not in use, making air available as needed by removing the cap at the area you're at next. Hoods are easy to make yourself using 1/4" plywood and use vents/pipe from Lowe's/Home Depot. Spray booth also but had to put damper in the pipe to slow the volume down for airbushing. Harbor Freight has some of these fans in smaller sizes. Quote Link to comment Share on other sites More sharing options...
bass100 Posted February 15, 2012 Report Share Posted February 15, 2012 All of my vent pipe is solid 4" until I need it to be movable then it is 4" flex hose. I vent to a window. I built a box to put the fan inside of and the box is mounted in front of a small window. I built an extension that slides into the front of the box (the exhaust) and that allows me to remove it when I want to close the window. The extension also allows me to not worry about wind blowing the smoke back through the window. Quote Link to comment Share on other sites More sharing options...
mark poulson Posted February 16, 2012 Report Share Posted February 16, 2012 I pour with an open garage door, and a 20" box fan blowing out from the rear of the garage. Most of the time, I pour on the driveway, so the fumes aren't as bad, but they are there. Years ago, I made a sawdust collection system for my garage, starting with two VR1000 exterior side wall mount fans which are both 10" diameter intake. They are explosion proof fans meant for remote Kitchen hood venting, and I salvaged them off a job I was doing. I made a collection box with a 35 gallon plastic trash can mounted below it. The sawdust is carried from which ever machine I'm using, up through 4" solid piping verticals into a 6" solid horizontal pipe that passed across the ceiling of the garage and dumps into the collection box. The 6" pipe actually dumps down into the trash can, which lets the heavier stuff precipitate out, and the finer stuff is pulled up into the collection box, through a screen and then a washable AC filter, and out through the side wall fans. In all the years I've been using this system, it has worked fine, with a teeny amount of fine dust collecting on the exterior wall below the fans. Not even enough to clean off. I put a plexiglass face on the collection box, so I could monitor the AC filter and know when I needed to clean it. Since I've used the system for sawdust for so long, I decided against trying to modify it for my plastic pouring. I was afraid I would mix sawdust and plastic fumes, and that might not be good. But I'm fortunate to live in SoCal, where I can pour outside most of the time. Quote Link to comment Share on other sites More sharing options...
creekbeater Posted February 17, 2012 Author Report Share Posted February 17, 2012 Thanks everyone for the feedback. After spending a few days and countless hours online looking at literally thousands of fans, talking to several hvac places etc, i just ordered a 6 in in line centrifugal duct fan the pulls 440 cfm under a load. It is a fan used for hydroponics and was $80 while other fans may be better suted for the task, all of them were nearly double or more in price. I should get it in a few days and will post picks of the completed job and let you know how it works. Quote Link to comment Share on other sites More sharing options...
Kajan Posted February 17, 2012 Report Share Posted February 17, 2012 I don't think you will have enough, you will need 2 of those 6" fans at min. Try it with the one, you can add side partition walls to help your draw. Make sure you have equal ammount of intake air coming into your room. Quote Link to comment Share on other sites More sharing options...
Smallie Posted February 18, 2012 Report Share Posted February 18, 2012 This is the fan I use. It moves any visible smoke away from my seat immediately and I don't smell any fumes. It is about 15 inches in diameter and I discharge directly through the wall. You may be able to adapt this style of fan by building a box above your hood and increasing the discharge pipe side. As Kajan commented, side walls will help concentrate the draw. 1 Quote Link to comment Share on other sites More sharing options...
