Where to vent kitchen extractor

[slicendice]

Has anyone had any experience of ducting kitchen extractors? I'm getting kitchen refitted next week (££ ouch ££!!!) and the current cooker hood apparently vents into the chimney (not good!) and I'd like to vent it outside. I've read that the max distance you should vent a kitchen extractor is 5m dropping by 1.2m for every 90 degree bend. Given that the extractor is located ~3m from an external wall and there would need to be one 90 degree bend, it should be OK but just wondering if anyone has ducted this kind of distance? Did it extract OK? Any pitfalls? 

[CWARD]

Previous house had a long 3m run like that but only along one wall to the external one. It was noisy! The cupboards that it ran along the top of seemed to magnify the sound. Pipe lagging reduced it bit but you couldn't put too much on without it becoming visible. When we originally moved in it was a flexible pipe that even louder, we changed to plastic oblong section which also helped.

[magic62]

Important, to silence the fan, is a diameter that is big enough to transport the air. 

If it is too small, the fan will start to flutter, because it cannot loose the air and will build up pressure. The pressure in the pipes will cause noise.

If it can run freely, it will become much more silent.

(my experience)

Edited 30 August, 2017 by magic62

[KenONeill]

Outside!!

 

Seriously, there isn't anywhere you can get a 30cm square of outside wall to vent through? Or did you actually mean the vent for an "extractor hood" over a cooker?

[slicendice]

36 minutes ago, CWARD said:

Previous house had a long 3m run like that but only along one wall to the external one. It was noisy! The cupboards that it ran along the top of seemed to magnify the sound. Pipe lagging reduced it bit but you couldn't put too much on without it becoming visible. When we originally moved in it was a flexible pipe that even louder, we changed to plastic oblong section which also helped.

 

There's a false ceiling in the kitchen and I'm hoping there's enough room to locate the trunking (smooth plastic, not ribbed) within the false ceiling so that might help reduce the noise a bit

[slicendice]

14 minutes ago, KenONeill said:

Outside!!

 

Seriously, there isn't anywhere you can get a 30cm square of outside wall to vent through? Or did you actually mean the vent for an "extractor hood" over a cooker?

 

Sorry, yes, I meant vent for an extractor hood over a cooker 

[S00perb]

Just make sure all the joins are 100% - I have seen the mess a leak makes up there (and what a waste of electric)

[Tilt]

The best thing you can do to keep noise to a minimum is to make sure the installers do not reduce the size of the outlet trunking..........

The extractor will probably come with a reducer 5" to 4" but this will make the extractor motor work harder, even more-so on a long run.

 

Ideally match the trunking diameter with the outlet diameter of the extractor. Probably 5" / 125mm (if it is a reasonable quality extractor). rather than the 4" stuff.

Also if you can make the bend more gradual, or use two 45° bends instead of one 90° piece. Smooth / ribbed will not make a noticeable difference if at all imo.

 

Look at screwfix ducting and ventilation if you need ideas for materials. Good luck with it all.

[Tilt]

2 hours ago, slicendice said:

 

Sorry, yes, I meant vent for an extractor hood over a cooker 

 

You mentioning that the "current cooker hood apparently vents into the chimney" left me in no doubt as to what you were asking about!

Kind of gave it away, Lol.

 

Some folk need to read........................ Ken .................................

Edited 30 August, 2017 by Tilt

[VWD]

Problem with venting outside ( unless outlet has a secure leakproof shutter ) is similar to what I used to have with my central heating vent , made worse by fact that wall with vent faced into prevailing coldest wind ,where temperature within kitchen was almost that of outside.

[Tilt]

^^^ Valid point.........

 

The other option is recirculating using Charcoal Filters (usually available if not provided) although this leads to extra load on the fan motor again therefore creating unnecessary extra noise - for those that it bothers.....

[SuperbTWM]

Make sure you use solid ducting where you can as the flexible stuff is horrid for airflow. I would say if the extractor is of good quality and has a good flow rate you will be totally fine. 

 

The filters that recirculate the air are ok but because your not getting rid of the moisture you can end up with a humid kitchen and a bit of condensation on the windows in winter (especially if your missus is a complete retard and never puts lids on pans when boiling and insists the max setting on the hob is the only way to cook)

[Tilt]

13 hours ago, SuperbTWM said:

especially if your missus is a complete retard 

 

. I hope your missus don't read this......................................Or has an excellent sense of humour, Lol.

[Bignij]

13 hours ago, SuperbTWM said:

(especially if your missus is a complete retard and never puts lids on pans when boiling and insists the max setting on the hob is the only way to cook)

Crikey. They must all learn to cook at the same place.