replace 4-inch bathroom extractor fan with 6-inch

[IanJ]

I'd like to replace my current 4-inch / 100mm bathroom extractor with a 6-inch / 150mm version - current one just isn't doing the job.

Current fan is ceiling-mounted and vents via flexible ducting through the loft and out via a soffit vent.

Screwfix sell a ceiling-mountable Manrose 6-inch fan, but I'm not sure (a) how to connect this to the existing 4-inch ducting (can't find a reducer anywhere) and (b) whether standard flexible ducting will be strong enough to take the pressure from the new fan (should be around 230m3/hr, rather than 85m3/hr from the 4-inch fan).

Thanks

 

[nstreet]

Why not get a 4in fan with a higher extract rate

 

[ChrisR]

Normal axial fans are pants in anything of a duct - like over about 1 metre. Centrigugal fans are made for the job. Trouble is they're usually in boxes which look pants.
If it has never to your knowledge worked, check there's a way for new air to get INTO the room. (Try with door open). It's amazing how many people expect steam to be sucked out of a closed box. Solution is to trim the door bottom, or put a vent in it.

 

[slippyr4]

Chris,

I'm about to choose a fan for my bathroom, which I want to duct. But i'm not sure I appreciate the difference between axial and centrifugal fans - can you shed some light

cheers

slip

 

[IanJ]

Thanks for the replies

nstreet - the only 4-inch fans I can find have a standard extract rate of around 85m3/hr - can you suggest higher-rated alternatives?

ChrisR - it is a bit better with the door (or the window) slightly open, to get some air into the room ... but it's still pretty rubbish. I've never yet lived in (or visited) a place where a 4 inch bathroom extractor fan does much good

I'd like to know the difference between axial and centrifugal fans, too!

 

[nstreet]

This may help with the techie bits;

http://www.vent-axia.com/sharing/whatisafan.asp

Slightly higher rateExpelair 92/m3 p.h. http://www.plumbworld.co.uk/666-2704

or convert to one of these if you have the clearance in the ceiling: http://www.tlc-direct.co.uk/Products/SLTD250.html more here http://www.tlc-direct.co.uk/Main_Index/Ventilation_Index/4_Inch_Fans_Duct/index.html

 

[IanJ]

That's great nstreet - thanks very much. I'll be going for the inline fan kit - plenty of space up in the loft.
Cheers