Noise at exhaust vent, upsize from 4" to 5" or 6" good idea?

[Tompo]

I have a problem with my exhaust vent being quite noisy, my fan is 5" 235cfm (400m3/h) and running 5" ducting to a 4" exhaust vent.

I have a muffler just before the vent and that did a pretty good job but the noise from the airflow is still quite bad. Would upsizing the vent to 5" make a big or any significant difference? 6" is possible too but don't have the tools for that.

Opinions or experiences? Thanks!

 

[Andyo]

6 in"

6 in"

yes 6 inch would be better less air speed same volume.
If your going through brick work you could hire a 6inch diamond core bit i have a set of core bits makes a perfect smooth hole but youll need hire a big drill with a clutch.
The other way would be 6 inch fan on half speed about the same amount of air,thats the best trick.A

 

[Tompo]

Thanks for the info! Luckily the wall is wood and insulation between.

If I would go with the 6" hole and having my ducting (the muffler too) 5", how long should the widening of ductwork be? The wall is about 25cm / 10", will that be enough to avoid air getting turbulent from the widening of the duct? Edit: (english not my first language as you might have noticed) I mean, having these duct adapters that are a few inch long cannot be optimal, is there a rule of thumb to measure the length for the duct upsizing?

I would not want to replace the fan & ductings to 6" but I understand that would do good too. I guess the 6" opening would be the biggest thing, am I close? The fan itself is not close to the opening so the airflow has a good time to get from turbulent to nice flow so is there a big difference having larger ducts and fan too in this case?

 

[Tompo]

Decided to go with 6" (or 160mm that is, a little larger than 6"). Should drop the airflow speed to about 1/3 of the current with 100mm (4"). I'm now wondering if the muffler, ducting and fan should be upsized to 160mm too as Andyo said it would reduce the noise even more.

Anyone have experience on this? Should I go straight away and do the job of replacing everything (money issue, but if its worth it, then yeah) or just widen the exhaust from 100mm to 160mm?

 

[Jnugg]

To reduce noise of the air wooshing around in the ducting,buy oversized ducting,also use insulated ducting.

 

[willyweed]

hiya tompo,have a look at this thread for all the information you should ever need to do with fans ,airflow etc. good luck willyweed https://www.icmag.com/ic/showthread.php?t=112862

 

[willyweed]

peace

 

[Andyo]

double size half speed

double size half speed

Normally i go double size half speed that helps loads and leaves options for increase in hot weather,.A