Cooker in chinmey breast - can I duct up the chimney?

[Gossamer]

Evening,
I have opened up the chimney breast in my ~100yr old house kitchen to put in a oven and hob. The plan is to install a canopy extractor.
Ducting through the kitchen is proving a nightmare due to it being on the party wall and various other constraints, some structural.
Anyway, several kitchen companies have said just vent into the chimney, other opinions say definitely don't. An extractor manufacturer said today just buy a powerful extractor, install a duct into the chimney and use that, it will reach the top (!).
Confused - is there a definitive approach?

 

[Doggit]

If you duct directly up the chimney, it'll just collect moisture residues etc inside it, plus the fan won't be powerfull enough to push the fumes that far. If you used ducting, then as anything hot from the pans condenses on the cold ducting, it would run back down to the extractor, and eventually ruin it. In addition, the rain would come down the ducting if left open, and restrick the outflow if you have a chimney cowl fitted.

I cut a hole in the side of the chimney, used a curcular tubing to get out into a flat channel ducting, and then took that along the ceiling on top of the kitchen cupboards, and out through the wall.

Post some pictures.

 

[Gossamer]

Ok here’s the situation. Some photos showing the layout. The joists are working with me but the chimney breast is on the party wall and there are constraints such as lecky, CH pipes and the two kitchen windows, doorway etc. Thinking two options if not ducting up the chimney but its tight in the ceiling and I really need 5'' min ducting, round or rectangular.
1. Core drill through the chimney into the ceiling void and duct along the ceiling using 5-6’’ rectangular flexible ducting to dodge the lecky and CH. Emerges close to the existing windows which I gather is a no no (???).
core drilling through the chimney worries me but surely a 5-6'' core wouldn't affect the chimneys integrity..???
2. Core drill through the side then route along the top of wall units (to be fitted) then hop into the ceiling before the doorway and out the wall. Same window issue again I believe.

 

[Doggit]

Looks as though you need flat channel ducting for that, but metal would be better as no joints. What's the outlet size of the extractor, and do you know the distance it will push the exhaust fumes.

 

[Gossamer]

Looks as though you need flat channel ducting for that, but metal would be better as no joints. What's the outlet size of the extractor, and do you know the distance it will push the exhaust fumes.

the smeg unit I'm looking at is 6'' but comes with a 5'' adaptor. not sure about the distance, its 250m3h but that's the volume I think.

 

[Doggit]

You don't want to reduce the size of the throat, as that'll just make the motor work harder, and increase the noise. You'll need to see if you can get an adaptor, but have a look at https://www.naplesuk.com/ducting to see your options.

 

[Gossamer]

You don't want to reduce the size of the throat, as that'll just make the motor work harder, and increase the noise. You'll need to see if you can get an adaptor, but have a look at https://www.naplesuk.com/ducting to see your options.

If using the 220x90 flexible hose (6'' duct capacity) does it matter if there is contact with CH pipes etc?

https://www.naplesuk.com/3-metre-rectangular-flexible-pvc-hose-220mm-x-90mm.html

 

[Doggit]

The ducting could expand and contract a bit with the heat, so you'd need to try and fit a bit of insulation between them if possible. You want a slight fall if you can get it, and putting some sealant round the joints and then taping them with duct tape wouldn't go amiss either. Once this is in and plasterboarded, you've got no access to it, so do the job carefully. If you've got a bit more space, I'd even go as far to glue or Duct tape a couple of 1x1 battens to it to make it as rigid as possible.