Extractor fan ducting 125mm to 100mm

[Oliver Brearley]

Hi,

Can you help ? The overhead extractor fan that I've purchased to go over our hob has a plastic adapter on it. This attaches to the extractor hood and goes out on circular 125mm (~5"). Although there are parts an accessories for 125mm there are far more for 100mm (~4") to build the ducting to the outside world.

Do adapters exist that take 125mm circular to 100mm circular, or to push my luck :-P 125mm circular with 90 degree bend to rectangular

100mm x 55mm ?

-> If so where ?

I've already found my bodge solution and that is to use a 100mm threaded hose connector with plenty of ducting sealing tape ! But I thought we'd try and do the correct way first.

Cheers - Oliver.

[rrh]

Do you really want to do this? The kit will expect 125mm and by cutting that down to 100mm you will be severely restricting the airflow. I have just taken delivery of a new cooker hood with 125mm outlet and while I agree that it's more difficult to get 125mm ducting stuff than 100mm - especially with the ducting in aluminium which I wanted because it's going to be visible - it is possible. Try:

I found it astonishingly difficult to get hold of their stuff even when I had identified the exact part numbers from the catalogue - nearly all the stockists suggested by the manufacturer said they weren't (stockists that is) or had a few bits only in stock and couldn't/wouldn't order the less common stuff for me. Domus did eventually point me to Starkey Systems on

01905 611041 or and after a couple of failures the stuff arrived mail order.

[Ian Stirling]

It depends. IIRC, the restriction is about 2.5 times for 100mm pipe. So if you'r using 1m of 100mm pipe, it'll be similar to 2.5m of 125mm pipe.

[TheScullster]

Not too sure of your layout, but better to go up in duct size than down! That way you get 6" (150) stuff - readily available and (more importantly perhaps) you decrease rather than increase the velocity for a given air flow - therefore should be less noisy.

Phil

[Oliver Brearley]

Thanks to all that have replied, you've given me plenty to think about. I should have provided some details of the ducting run I'm thinking of doing. Some of the points made would be very valid on a larger run, but I'll be sure to consider them in this run that is just less than 2 meters. To give you an idea of where I up to on this 'do-er' up property, please see the URL below.

Thanks to all that took the time to reply.

- Oliver.

[John Armstrong]

Screwfix part 10684