Havac exhausting air with fan from laser engraving machines

[JohnyJon]

I have a question We have machines that need a fan and duct work to suck air and ventilate the air outside. We have a 2hp fan that is 1500 cfm. Couple of questions.
1: we have a roof stack with a cap on top. The duct is galvenized, it runs about 15 ft from fan to the exit. There are 2 45degree turns using 6in duct. Is there any chance we are over powering anything?

2: we want to connect to machines to this same fan. This will require connecting 3 ducts using splitters or what ever they are called that all funnel into one input of the fan. After that it follows the same rout stated above. - the machines are about 5ft and 15ft away from the input of the fan. And there will be one 90degree elbow.

Do you see any problems with this ?

Attached is a photo of the fan inside a box to isolate sound. From there the duct goes up then there is a stack in the roof.

with question number 2. There will be two machines connected to this one box (the fan) you see one big machine and there is a smaller machine to the right on the other wall.

ideally we would like the one fan to suckair out of both machines. We also want to make sure we are not possibly causing an issue with such a strong fan and 6in duct as shown. We also want to make sure the fan IS strong enough to pull air from both machine. One machine uses two ducts to be connected to fan. The other machine uses one duct. And the fan has one input. So we will have to connect all ducts together to funnel into the fan etc..

thanks I’m advance

 

[Sir Buck]

You are definitely on the correct path to ensuring that you preserve good IAQ (indoor air quality) in the living space.
Most building codes require outside make-up air if any exhaust is moving indoor air out of the living space and is more than 300 cfm. And there needs to be an interlock to open dampers and, if powered, to start fans to bring the outdoor air into the living space.
A 6-inch duct is not nearly large enough to move 1,500 cfm.
I have a 500 cfm range hood and that required an 8-inch duct.
And if you are moving 1,500 cfm out of the living space, that is going to disrupt the operation of the heating and/or cooling system by moving conditioned air out and bringing in unconditioned air. Typically if that much air is being exchanged, an air-to-air heat exchanger is used to keep your energy costs down. Depending on where you live in the USA, this would be an Energy Recovery Ventilation (ERV) or a Heat Recovery Ventilation (HRV) system.
I would suggest that your ventilation project is beyond a DIY project and you should consult with an HVAC contractor to give you some advice about how to go about this.
Best wishes.
J

 

[AC Power]

Is your exhaust fan a forward incline centrifugal, backward incline centrifugal fan, propeller, or axial fan? This is relevant as some of these fans will stall (in air flow) if the exhaust "head pressure" is too high.

The use a "splitter" is what you would need, yes. However, you would likely need to have this custom built at a pre-fab tin shop. It's not expensive to do this.

IMPORTANT: Lastly, you have to consider what kind of a room AND house/building are you putting this in? When your pulling 1500cfm of air out of a building, your going to create a negative static pressure. I can tell you what this means, and if it can be avoided easily. What kind of a room AND what kind a structure is this prospectively to be installed?