Extractor fans over cookers

N

nev

Guest
Hello, we are building at the moment and want to have the cooker and extractror on an inside wall.. It is 16 feet to the ouside wall ..... does anybody know if this is too far a draw for an extractor fan.... or is there a make of extractor fan to do this length.. I hear the charcoal extractor fans are not much good... moving the cooker is not an option..
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nev said:
Hello, we are building at the moment and want to have the cooker and extractror on an inside wall.. It is 16 feet to the ouside wall ..... does anybody know if this is too far a draw for an extractor fan.... or is there a make of extractor fan to do this length.. I hear the charcoal extractor fans are not much good... moving the cooker is not an option..

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Hi'

My wife and I baught a house builders finish and wanted the cooker and extractor fan in the middle of the room on an island.
Its about 15ft away from the external wall and I piped it out.
it works fine and is the usual 4" extractor hose.
No problems after 3 years.
Hope this helps.
 
Hi Adrian.... had you to get a particular make or model or get a more powerful fan ... thanks for your help
 
This is done all the time in apartments and should not prove a problem with most fans; the real problem for fans "pumping" this distance is the friction offered by the actual ductwork/ pipe and any bends. You can minimise this by using a proper rigid pipe for the ductwork as opposed to fexi pipe (restrict the use of this to the start or end of the run where possible) as the smooth internal bore offers the least resistance to airflow. 3 and 4 metre duct runs are not uncommon in apartments (for kitchen and bathroom extracts) so I wouldn't worry too much about it. Make sure to seal any joins in the ductwork with silicone and/ or duct tape as appropriate. It's a good idea to lay the duct with a small fall (1: 100) towards the outside as this ensures any condensate will not lodge in the pipe.
 
Also look at the specs of the extractor fans, there is a massive difference between cheap & cheerful and a decent fan. I did a rework on our kitchen a few years ago & spent a fair bit on a fan to do the job. I selected the fan based on it's throughput, I forget the specification but if you ask, it will become apparent which are the good ones. Unfortunately you will pay a lot for design also. Well worth having a fan that will take ALL of the steam from a few boiling pots, as this moisture is not good for your house.
 
All fans should come with information on their performance, wattage and m3 are the two figures to look for, but even the best fan will perform poorly if the ducting is badly designed or executed.
 
Carpenter said:
This is done all the time in apartments and should not prove a problem with most fans; the real problem for fans "pumping" this distance is the friction offered by the actual ductwork/ pipe and any bends. You can minimise this by using a proper rigid pipe for the ductwork as opposed to fexi pipe (restrict the use of this to the start or end of the run where possible) as the smooth internal bore offers the least resistance to airflow. 3 and 4 metre duct runs are not uncommon in apartments (for kitchen and bathroom extracts) so I wouldn't worry too much about it. Make sure to seal any joins in the ductwork with silicone and/ or duct tape as appropriate. It's a good idea to lay the duct with a small fall (1: 100) towards the outside as this ensures any condensate will not lodge in the pipe.
Click to expand...

Thanks for the advice just one thing, we have precast concrete floors upstairs so we are limited to how much we can drop the celling, i'm after coming across a flexi pipe 120 x 60 and I can get the fixings to suit. Would any know if it is possible to a rigid pipe in those dimensions to suit the extractor.
 
we had the same issue recently with an island hood

extractor fans have a 4"(100mm), 5"(125mm) or 6"(150mm) extract - you have to use the correct size ducting to get the published performance from the fan (it's usually forbidden under the terms of the guarantee to reduce the size of the ducting on the exit from the fan)

Elica, Neff, Siemens are usually 150mm
DeDietrich, Baumatic are usually 125mm
Miele are usually either 125mm or 150mm, with a higher m3 t/put for 150mm

best to check with the vendors

you can get rigid round ducting in these sizes, plus the equivalent flat ducting and converters - the 5inch equivalent being 205x60mm, so it fits under a standard batten.

I have an email reply from the Elica distributor in the UK that it is usually acceptable to have a total of up to 15m of ducting for a 150mm extract with:
* 1m of rigid ducting counting as 1m
* 1m of concertina ducting counting as 2m
* each turn counting as 1m

the main problem is condensation inside the ducting so it's a good idea to run the fan on full blast every so often and NOT increase the size on the way out

another option is to have an external motor and a motorless fan - but these are expensive and the motor is usually quite large and AFAIK must have 6inch ducting

for the record we bought a DeDeitrich tube fan as we already have 5inch flat ducting fitted in the ceiling

another thing to watch is that, if you have higher-then-normal ceilings is that the fan can extend down to an appropriate height - as luck would have it this only rules out the cheaper ones!
 
Where can you get the rigid flat ducting and converters.. I have tried a few places but had no luck....
 
B&Q stock it, as I'd imagine most of the proper builders providers do.
Leo
 
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