vent going from 6 inch to 3 inch?

[Arbe0]

I installed a exhaust hood a long time ago, was wondering if it would work better if the duckting didn't go from 6 inch to 3 inch outlet. I can take off the 3 inch and just extend the 6 inch if that would help out.

 

[NTBeer]

There are better qualified people around here to answer this, but in a nutshell, yes. A 3 inch outlet can only handle 1/4 of the flow the 6 inch section is carrying.

 

[day_trippr]

Of course it would help - and why would one have done that?
The cross section area difference between 3" and 6" diameter ducting is 4X...

Cheers!

 

[Vale71]

There are better qualified people around here to answer this, but in a nutshell, yes. A 3 inch outlet can only handle 1/4 of the flow the 6 inch section is carrying.

That's not correct. Air is a gas and will just accelerate when going from 6 inch section to 3 inch section but there is indeed an increase in resistance which will reduce flow although not as dramatically. So in a nutshell if it's not too complicated to extend the 6 inch section then it's best to do so even if the benefit might not be as large as expected.

 

[BBBF]

I installed a exhaust hood a long time ago, was wondering if it would work better if the duckting didn't go from 6 inch to 3 inch outlet. I can take off the 3 inch and just extend the 6 inch if that would help out.

It would work better, but have you had any issues since "a long time ago?"