Ducting set up - when to reduce from 10" to 6" ?

[rtyuiop]

Hi folks,

Trying to work out a ducting design. My shop is roughly L shaped, and my plan is to put the DE (a second hand 5HP twin bag unit with an impeller of unknown efficiency) outside the shop, roughly on the outside corner of the L. Something like this:

      
         _________________________
         |                        |
       DE|                        |
         |                        |
         |          ______________|
         |         |
         |         |
 	 |         |
	 |         |
 	 |         | 		 
  	 |_________|

The DE has a 10" inlet, and I am planning to run 6" duct down each leg of the L, with assorted drops along the way. My question is: am I better off running 10" ducting into the shop and trying to split it into two 6" trunks there, or should I reduce to 6" as soon as possible after the inlet, and enter the shop and split all at 6" ?

Running 10" seems like it's going to be painful and expensive even for that short distance, but if it should give me a reasonable gain in airflow if might just be worth it.

Regards,

Danny

[shedman]

Hi folks,

Trying to work out a ducting design. My shop is roughly L shaped, and my plan is to put the DE (a second hand 5HP twin bag unit with an impeller of unknown efficiency) outside the shop, roughly on the outside corner of the L. Something like this:

      
         _________________________
         |                        |
       DE|                        |
         |                        |
         |          ______________|
         |         |
         |         |
      |         |
     |         |
      |         |          
       |_________|

The DE has a 10" inlet, and I am planning to run 6" duct down each leg of the L, with assorted drops along the way. My question is: am I better off running 10" ducting into the shop and trying to split it into two 6" trunks there, or should I reduce to 6" as soon as possible after the inlet, and enter the shop and split all at 6" ?

Running 10" seems like it's going to be painful and expensive even for that short distance, but if it should give me a reasonable gain in airflow if might just be worth it.

Regards,

Danny

My advice would be to keep the larger run as long as possible so long as the impeller has the power to keep the dust moving and not let it settle.

[BobL]

Unless you run more than 1 machine t the same time, or will be using lots of long (10m) runs, or you want to be able to rapidly vent the shed, then even 8" is a waste of money
AND
There is a risk that sawdust will fall out of suspension in the larger ducting when one machine on 6" ducting is used.

For single machine and DIY use you might as well go from 10" to 6" right next to the DC.

For efficient air flow the transition from 10 to 6" should be over a distance ~10x the difference in the diameter of the larger ducting i.e. (10-6)x10 = 40"
But that is going to be hard to find or make and will take up a lot of room.
Just get as long a tapered tube as you can find - I used a plastic flower pot.
The Polycarbonate window is so I can get in and clear the impeller if needed.

[rtyuiop]

Makes sense - I think given I don't know how much air the impeller will move I will take it down to 6" straight away and avoid possible issues with not having enough velocity.

Thank you guys!

[rtyuiop]

I've cobbled together a BobL-esque flowerpot reducer - thanks for the idea, Bob! Will post pictures of the ducting when I get everything installed.