Cooker hood extraction up Rayburn flue

[Jo the boat]

I've posted the same question on the electricians forum too.
I'm a general all-rounder. Renovating a 150-year-old cottage.
I've just removed an old Rayburn and want to vent the fan-assist cooker hood up the flue which is cast iron and looks to go all the way up to the chimney from ground floor through the roof (2 storey house - 4-meter run?). It's approx 150 mm diameter.
I'll install a suitable cowl on the chimney.
Is this possible?
Thanks, Joe

 

[Darren Jackson]

Providing that no fuel burning appliance is been served by the flue, & it is effectivley redundant, then yes you can use it to vent the extractor to atmosphere. Much better than recirculation. You may want to carry out a flue flow test just to make sure it is not blocked and it's integrity is intact and not spilling into other rooms or the loft space higher up.

 

[Jo the boat]

Providing that no fuel burning appliance is been served by the flue, & it is effectivley redundant, then yes you can use it to vent the extractor to atmosphere. Much better than recirculation. You may want to carry out a flue flow test just to make sure it is not blocked and it's integrity is intact and not spilling into other rooms or the loft space higher up.

Thanks Darren. I can see straight up the disconnected flue to the sky! It is either cast or clay of some sort. It's round anyway and looks pretty clear from below. Really just worried about condensation running back down. There will be an 'S' between top of extractor and the bottom of the flue so maybe I could put in a moisture trap?

 

[Darren Jackson]

Yes but make sure you can get to it to clean it out occasionally.

 

[johnduffell]

No you can't do that unless you put a condensation trap in, every time you vent some steam it will run bbac down the walls. Horizontal and as short as possible, and insulated if in a cold space.

 

[Jo the boat]

No you can't do that unless you put a condensation trap in, every time you vent some steam it will run bbac down the walls. Horizontal and as short as possible, and insulated if in a cold space.

Thanks John
Using the flue WILL cause problems at some stage so I've had a re-think and will vent horizontally through an exterior wall (3m away). My thinking is that vertical flues are for things that burn continually (solid fuel appliances / AGAs etc.) and use the warmth of the flue to draw. A cooker hood is not in this category.
Thanks all for your input.