Extractor Fan Vent - Guidance?

  • Thread starter Thread starter Deleted User 298457
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Deleted User 298457

Deleted User 298457

Hi folks,

My new extractor fan arrived today. It has a diameter of 150mm which seems immense. I only have a core drill up to 110mm.

Is 150mm "recommended" dia and should I:
a) buy a new core drill and crack on

or

b) it is overkill and buy a reducer.

There is no guidance with the unit itself other than a diagram of it being vented.

Thanky ou
 
Yeah it was quite the surprise to see how chungus it was...

D6YC6Ne.png


I guess I buy a 150 to 125, and then a 125 to 100 and go with that.
 
Any bright ideas on reducers? I can only find 150 to 120 and 125 to 100, not sure I'd get away with it!
 
That’s right.

You’ll need to go for 150-120 then 125-100, the 125 slides over the 120 connection.

You need to (depending on brand you might not) get a 150-150 coupler that fits inside the pipe and fits inside the reducer as well. As the 150 pipe to 150-120 reducer are the exact same size.
 
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Reuben klang said:
That’s right.

You’ll need to go for 150-120 then 125-100, the 125 slides over the 120 connection.

You need to (depending on brand you might not) get a 150-150 coupler that fits inside the pipe and fits inside the reducer as well. As the 150 pipe to 150-120 reducer are the exact same size.
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Camping out in Screwfix parking lot it is!

Bug One said:
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Hmm yes maybe I should stop rushing it.

---

On the flip side, any religious reason not to do 150? Air flow will be same but at higher pressure with 100mm? (Is that physics?)
 
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Buffman said:
If you use rigid ducting 100 will be fine.

You will have an increased pressure loss using smaller diameter and consequently reduced flow but you will be fine either way.
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This ^

Basically by squeezing the pipe size die you're mostly restricting the fan from working at its best, there's not much flow <> pressure conversion. But I'm sure it will work fine and bigger fan = better IMO.
 
From your image it doesn't look like the external height of the extractor is a problem, but if it is or is in the future, get one of these:


I wish I'd know about them before I hired scaffolding to fit my extractor outlet!
 
I stepped down from 6" to 5" but the run was only stepdown ring, 90 elbow and out the wall, very very short, apparently the only issue comes in longer runs and increase in noise through the narrower ducting.
 
I think I may just go 150mm. I'll have to rent a core drill bit that size but just don't want to risk added noise.
 
Classic Blue Theme said:
I think I may just go 150mm. I'll have to rent a core drill bit that size but just don't want to risk added noise.
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If you're going straight out I wouldn't stress too much about the noise, certainly with mine there's nothing unpleasant over any other extractor I've previously had, biggest noise complaint for me is trying to weigh down the flappy door enough that it does bang around in a storm.
 
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