Extractor hood and 130mm duct

Livingroom

Hi,

In my kitchen, I have a 130mm duct venting to the outside wall for the extractor hood. I am putting a new extractor hood in but all the ones that I've seen (like) require a 150mm duct. The length of ducting from the hood to the outside will be approx. 1.6 - 2m with one 90 degree bend. Would it cause a lot of damage to the extractor motor to use 130mm duct instead of 150mm? And at these measurements would the motor efficiency be dramatically reduced?

Thanks,
Aisling

jack of all

I'm no mechanical services engineer but a 130mm duct represents a 25% approx. reduction in cross sectional area, which is obviously very significant, that plus a 90 degree bend will reduce performance dramatically. I'd imagine that increased noise might be the biggest concern here though. Others more knowledgeable might be able to chime in....

Idioteque

Could you not just drill a bigger hole? It'd save worrying about efficiency loss etc.

See if a friend/neighbour might do it for a few beers or if not, advertise for someone to do it - prob cost around 70e but you might be able to bargain down to 50e

listermint

You won't get a 150 mm hole bored for that money.

Could have it shipped out and cemented in for by any hand man.

But a boring drill is expensive and a pain in the hole to use

Idioteque

From a quick look at Donedeal there's two different people (Cork & Limerick) charging €80 and €50...

Calahonda52

there are two issues here:
the ducting and the hole through the wall.
You need to use the proper rigid smooth wall ducting certainly up to the hole in the wall.
You may find that enlarging the existing hole may be an easy enough job so go have a good look.

You wont get the existing hole drilled out to 150, it wll have to be chipped out: not a hard job, just drill a circle of 6 or 8mm holes, close together around at 160mm diameter all the way through the wall and then up the bit size to say 16 mm and then chisel out the remainder