• I want to thank all the members that have upgraded your accounts. I truly appreciate your support of the site monetarily. Supporting the site keeps this site up and running as a lot of work daily goes on behind the scenes. Click to Support Signs101 ...

Exhaust Fan Question

C

CanuckSigns

Active Member
I'm hoping someone here can shed some light on a question I have. i currently have an exhaust fan in my print room, I will be adding another piece of equipment that needs venting. The current fan is a 6" duct fan, outputting around 430 CFM. would I be able to replace the fan with an 8" one and add a 8"->6" reducer for the final 4' run out the back wall?
the setup would be"
8" pipe for about 15 feet, into an 8" inline fan, then a 6" reducer then 4 feet of 6" pipe out the back wall.
Cutting a larger hole in the back wall is not an option, landlord won't allow it.

i know the reducer will create a bit of a choke point, but if the 8" fan is rated for 900CFM, would it still pump out more air than a 6" rated for 430CFM?
 
C

CanuckSigns

Active Member
Gino said:
What's the size of the room itself, including the ceiling height ??
Click to expand...
the current print room is about 15'x20' with 8 foot ceilings. the current fan just helps to get the ink smell out on long print runs. I will be adding a laser cutter and am hoping to tie into the existing duct work that runs out the back of the building, I'm wondering if swapping the 6" fan @ 430CFM to an 8" fan @ 900 CFM will have any benefit if the last 4' of ductwork is still 6" or am I going to create a bottleneck?
 
Gino

Gino

Premium Subscriber
I agree with wey. 400 is barely enough for a vent roof to get the smells of a small kitchen out. You have quite a bit more space and wanna add a second machine.

Our shop has two large exhaust fans which both do around 5,500 cfm. We're exhausting about 8,000 sq ft. Also have 2 smallr ones we can use, but it's like a mouse p!ssing in the ocean.
 
W

weyandsign

New Member
They make 10 to 6 reducers. As far as causing issues, not sure what you mean. I would think more air being sucked out the better.
 
Gino

Gino

Premium Subscriber
By law, down here..... many exhaust fans are to be inspected to make sure they are passing allowable amounts of whatever they are passing to the outside. Some inks, paints and even laser engraving odors can produce harmful air outside. Just simply passing it outside just means you are making it easier on your employees, but not giving people outside any protection. Just because it helps your people does not translate to the environment. Just food for thought.
 
C

CanuckSigns

Active Member
weyandsign said:
They make 10 to 6 reducers. As far as causing issues, not sure what you mean. I would think more air being sucked out the better.
Click to expand...
the issue i'm asking about is if a 10" fan blowing into a 6" pipe is going to create a bottleneck and cause less air to flow through than if I just stuck with a 6" fan in a 6" pipe
 
N

netsol

Premium Subscriber
Gino said:
By law, down here..... many exhaust fans are to be inspected to make sure they are passing allowable amounts of whatever they are passing to the outside. Some inks, paints and even laser engraving odors can produce harmful air outside. Just simply passing it outside just means you are making it easier on your employees, but not giving people outside any protection. Just because it helps your people does not translate to the environment. Just food for thought.
Click to expand...
gino,
i wouldn't let passersby stand by my exhaust fan "huffing" the fumes from my printers

to increase the efficiency of the fan, you should have a small damper that can be opened on heavy printing days

when we use the exhaust fan in the kitchen i crack a kitchen window open 1"
the effect is dramatic.

you can read on the internet what they discovered when we started over insulating buildings.
i think they call it "sick house syndrome" you can make the fan as large as you want if there is no fresh air intake.

hvac people have baffles that open when the 24v fan relay is activated & closes when the fan stops
 
W

weyandsign

New Member
CanuckSigns said:
the issue i'm asking about is if a 10" fan blowing into a 6" pipe is going to create a bottleneck and cause less air to flow through than if I just stuck with a 6" fan in a 6" pipe
Click to expand...
I don't think. But even if it did bottleneck it, a 10" fan would still put a 6 inch fan to shame. The CFM is just so much greater it's a huge difference. And yes like netsol said, fresh air intake from somewhere is a good idea.
 
J

JSIGN

New Member
Not anything I've studied, but experience tells me that the air flow will just be faster while pushing through the 6" exit point ( like pinching a garden hose to get water shooting out farther ) - but the overall system upgraded to an 8" fan would certainly be evacuating more air.
Only downside I see is that the 8" fan will work a bit harder since it does not have the optimal exhaust port, but hopefully the fan can manage the 25% reduction - if you had to push through a 50 ft long exhaust pipe it would probably add comparable strain ).
 
Johnny Best

Johnny Best

Active Member
You need a air scrubber, Canadian company named Allen Air makes them.
VOC from ink is heavier than air and hangs low to the floo.
 

Attachments

  • IMG_9786.jpeg
    IMG_9786.jpeg
    1.6 MB · Views: 20
Last edited:
N

netsol

Premium Subscriber
weyandsign said:
I don't think. But even if it did bottleneck it, a 10" fan would still put a 6 inch fan to shame. The CFM is just so much greater it's a huge difference. And yes like netsol said, fresh air intake from somewhere is a good idea.
Click to expand...
it will raise pressure in the pipe.
STILL vastly better off with bigger fan even with a smaller pipe
 
Gino

Gino

Premium Subscriber
Even though you don't stand at the cow's a$$ or breathe these delightful aerosol cans, it still effects everyone. It's entirely up to the individual just how responsible you wanna be...... until some complains, then it's a matter of law VS. What you're doing
 
White Haus

White Haus

Not a Newbie
Gene@mpls said:
The fan should be as close to the machines as possible- learned my lesson on a 130w Laser burning plastics.
Click to expand...

We just installed a 130W a couple of months ago and have one of the 8" AC Infinity fans CanuckSigns is looking at. Man that thing moves a lot of air!! It's mounted half way between the laser and the hole in the wall - I would think you want more pull than push, assuming everything between the laser and the exhaust outside is air-tight? (Seems to be lots of conflicting opinions on this, from what I've seen)

We did recently realize that we had quite a bit of fumes leaking out between laser and exhaust - paid a good chunk of change for a HVAC company to set up some nice ductwork for us but they still didn't seal all the seams, and the flex tube going from unit to rigid tube had enough slack that the AC Infinity fan would just about suck it shut. We cleaned things up a bit yesterday and I think we've improved the airflow and reduced the amount of fumes leaking into the shop, it was getting pretty bad after a full day of running lamacoids.

CanuckSigns : You could always just run your theory by an HVAC guy - they'll know the answer. Assuming you just want to do the work yourself, it might be worth getting someone down to have a quick look/consultation even if you have to pay them for an hour. Otherwise just build it and test it out, can't hurt.

I'm not expert but I think you will choke some of the airflow, but it will still work. Those AC Infinity fans are insane, I've never seen anything like it.

Is there any way to plumb this setup into your laser exhaust ducts or different area of the shop? I've seen that, were people have multiple units all connected into one central exhaust.

Ah, the joys of adding new equipment and all the modifications that came along with it!
 
W

weyandsign

New Member
White Haus said:
We just installed a 130W a couple of months ago and have one of the 8" AC Infinity fans CanuckSigns is looking at. Man that thing moves a lot of air!! It's mounted half way between the laser and the hole in the wall - I would think you want more pull than push, assuming everything between the laser and the exhaust outside is air-tight? (Seems to be lots of conflicting opinions on this, from what I've seen)

We did recently realize that we had quite a bit of fumes leaking out between laser and exhaust - paid a good chunk of change for a HVAC company to set up some nice ductwork for us but they still didn't seal all the seams, and the flex tube going from unit to rigid tube had enough slack that the AC Infinity fan would just about suck it shut. We cleaned things up a bit yesterday and I think we've improved the airflow and reduced the amount of fumes leaking into the shop, it was getting pretty bad after a full day of running lamacoids.

CanuckSigns : You could always just run your theory by an HVAC guy - they'll know the answer. Assuming you just want to do the work yourself, it might be worth getting someone down to have a quick look/consultation even if you have to pay them for an hour. Otherwise just build it and test it out, can't hurt.

I'm not expert but I think you will choke some of the airflow, but it will still work. Those AC Infinity fans are insane, I've never seen anything like it.

Is there any way to plumb this setup into your laser exhaust ducts or different area of the shop? I've seen that, were people have multiple units all connected into one central exhaust.

Ah, the joys of adding new equipment and all the modifications that came along with it!
Click to expand...
I started with the AC Infinity 6 inch. It was ok nothing special, but I felt like I needed more power. I upgraded to the 10 inch and it's like a mini jet engine.
 
You must log in or register to reply here.
Top