Extractor fan with a 90 degree angle in the ducting???

[Jenny559]

Hi,

We are installing an extractor fan in out downstairs cloakroom which is in the middle of the house.

The problem is that if we run the ducting along the only suitable wall it is a span of approximately four meters and then when it reaches the outside wall it will need to have a 90 degree bend and a further span of approximately one meter to avoid a window lintel!

Can anyone tell me how effective my extractor fan will be with this setup???

Kindest Regards

Jenny

 

[mointainwalker]

Well Jenny, you will have to tell us what type of fan you have . Radial, centrifugal, in-line or what.

If it is new, some packaging/instructions give max run recommended.

You would also be well-advised to use rigid PVC piping of the correct diameter and not the flimsy concertina stuff, as the former provides much less resistance to air-flow.

 

[Jenny559]

Hi,

Haven't bought the extractor fan yet but was looking at quite a decent one from the Xpelair range - I think they are all centrifugal fans.

Once I have purchased it though I am pretty well stuck with it, even if I then discover in the instructions that the ducting can't span the distance I need.

Any advice???

Kindest Regards
Jenny

 

[mointainwalker]

Xpelair make all kinds of fans. The link below is to their centrifugal fans which is the type I beleive you will need

http://www.applied-energy.com/en/xpelair/products/range/1615

I couldn't find any info on max duct length, so unless you get a more definite answer here, then I suggest a mail to them.

 

[Burnerman]

Most of the conventional bathroom fans shift around 85 cubic metres of air per hour, and the maximum duct length recommended is 3 metres.
However, in line fans - i.e within the ductwork itself, shift over 200 m3/hr
and can handle ductwork of 10m. Much more expensive though!
Check out Screwfix 53730.
Thing is, you don't want to over extract so the overrun timer should be set for a short span.
John

 

[Blagard]

In-line or centrifugal fans are the ones to consider when pushing air through longer ducting installations. Axial fans are OK for short distances like straight through the wall

As noted elsewhere, use rigid type ducting, round or square, as this is more effecient than "flexible" type ducting.

Your other consideration may be noise. If you have a choice of fans lined up, check out the sound levels they produce (dB) lower figures are better. You will hear one running at 45dB whilst one at around 25bB should be very quiet. Ratings are often shown as dBA at 3m. The distance should be the same when making comparisons

For a cloakroom you will not need a heavy duty fan. The Screwfix 53730 noted elsewhere in the thread is way over the top!

I did notice that screwfix seemed to have good supporting information on many of their extract fans. You can download their manual on the fan you are looking at. Some of their small bathroom/wc fans indicate in excess of 9m duct runs using flexible duct!

You should not have any problems with the length of your proposed setup if you simply select a fan from the ones that indicate that length is OK