Vent/Hood Installation Questions
 

I have a 800 CFM squirrel cage fan with speed controller .
My room is 6' x 9' .
The fan will vent straight up through the roof -
There is an fresh air intake on the wall in back of me on the floor about 14x18".
I am on a HH ( for now and a while)
I will be putting acrylic baffels on either side of the hood4
• How high above my torch should the hood begin?,
• How deep does the hood need to be ( it will be 24" x around 36-40")
• Is it possible to put some kind of filter somewhere so glass particles don't get forced out with the fumes?
• How do you get the intake air to come up through the bench - •just cut a hole in the bench and maybe fill with screen?
•Does it need to be physically ducted there or will it find its way?

Thank you for endlessly helping on these frequently asked questions - everyones set up is so different! [-o<
Sally

1) Don't use the speed controller. Get rid of it, return it, sell it, whatever. A speed controller will only slow down the fan, reducing its CFM so some level that you do not know. Ventilation depends on known numbers. You have to know exactly what CFM you are moving.

The fan is properly sized for a 24" x 36" hood (calculates to 750 CFM, using 125 CFM per square foot). If by "depth" you mean the inside height of the hood from edge to flat mounting top, usually 12" deep is more than sufficient. All you need is an area to trap the fumes to prevent them from spreading throughout the room.

I'd put the hood anywhere from 24" to 30" above the top of the torch. If you think this is too low, you can raise it to no more than 42" above the torch. Any higher and you won't be drawing from the general torch area, you will be drawing from the general room, which isn't a good idea.

You don't need to worry about putting a filter on the hood. Large glass particles will not be drawn up into the ducting or into the fan itself. Even small particles will be exhausted normally through the duct system. Nothing would lodge in bearings or other areas that could cause damage. Additionally, filters reduce the efficiency of the air flow, which is something you absolutely do not want.

If you are going to use a surface mount fresh air source on your bench, it does have to be ducted from the source (the window) to the bench. Simply cutting a hole in the bench top will not bring the air up that way. It does have to be ducted. I'd recommend using the same diameter or larger than the exhaust ducting you will be using. Keep bends to a minimum, and use a standard floor register adapter to go through the bench top. That way you can then use a standard floor register to cover the hole, plus you have a way to close off the fresh air when the system is not in use.

Hope this answered some of your very good questions! If you need anything more described, please let me or Dale know! Good luck to you!

Thanks so much Mike!