Hob Extractor Fan height

GreeBo

Hey all,

I put in an extractor fan a few months ago (nice job drilling through porcelain tiles!) but I now think its too high as some smoke etc seems to get out past it.
Does anyone know what the "recommended" height is?
The measurements in the booklet are purely to avoid it getting damaged from heat (so a min height) but Im wondering whats normal?

Right now its 85cm above the hob and 176 from the ground.

cheers

10-10-20

What type of extractor is it and what type of cowling is surrounding it?

GreeBo

Thats her, externally vented.

10-10-20

I'll measure mine at home as it's a similar design buut is island based, but I know mine 'leaks' smoke also...
You may need a stronger pull from the fan... does it function better with the filters off? As to whether the height has much of an effect depends on a lot...

GreeBo

cool thanks
right now I have the basic wire mesh filters with charcoal and grease a catcher inside that.
Its probably overkill and killing some of my suction but otherwise I find that the motor gets manky with the grease
I might ditch the charcoal and see what that does

cheers

fm

650 to 750 mm is standard height above hob,also extractors dont have any suction (like a hoover),it pushs out any air externaly(or back into the room if using charcoal filters) that goes through the mesh.

GreeBo

fm wrote:

extractors dont have any suction (like a hoover),it pushs out any air externaly

surely if its pushing air out at one end its sucking it in at the other?
You can see/feel the suction inside the hood.
Obviously the pressure is not so strong as its over a large area but I think its incorrect to say it has no suction...

northdublin

GreeBo wrote:

surely if its pushing air out at one end its sucking it in at the other?
You can see/feel the suction inside the hood.
Obviously the pressure is not so strong as its over a large area but I think its incorrect to say it has no suction...

i think what he means is that the hoods are designed to collect the rising steam and then push it out the vent as opposed to drawing it via strong suction. if they did have massive suction they wouldnt need to be so wide.

10-10-20

Mine is 80cm from the cooking surface, and in my opinion, not high enough. As we have a 'cooking island' I continually twack my head off it.
It pulls in most of the smoke on the third setting.

GreeBo wrote:

right now I have the basic wire mesh filters with charcoal and grease a catcher inside that.
.....

I might ditch the charcoal and see what that does

Do dump it. It's externally vented so no need for all that malarkey other than to keep you on good terms with your charcoal/grease filter supplier... The manufacturers recommend that the charcoal filters are replaced every 6 mths... money making exercise!

ircoha

fm wrote:

650 to 750 mm is standard height above hob,also extractors dont have any suction (like a hoover),it pushs out any air externaly(or back into the room if using charcoal filters) that goes through the mesh.

yes they do, what is at issue here is the size of the intake surface.
The hoover, with a diameter of 2 inches will have an area of c 3.14 sq inches
the X fan with a surface area of 10 by 10 sq inches or 100 sq inches so about 32 times bigger, will not have the same suction per sq inch as the hoover, so there is sucking and blowing, which on reflection makes one wonder how u know what got its name, given that there is sucking without any reciprocal blowing:p .

OP: heightwise ours in 79cm over a gas hob:what I have done before is get a little apron or skirt about 25mm deep fitted along the two sides, it hold the stale air in long enough for it to be extracted

fm

northdublin wrote:

i think what he means is that the hoods are designed to collect the rising steam and then push it out the vent as opposed to drawing it via strong suction. if they did have massive suction they wouldnt need to be so wide.

yeah if the rising steam does not hit the extractor mesh it will not get extracted so on the outside there is no suction.the correct height is between 650 and 750 according to the manufacturers. maybe the problem greebo is having is when you use the filters you have to install a extra y shaped pipe to recirculate the air through the vents on the chimney pipe.

GreeBo

fm wrote:

greebo is having is when you use the filters you have to install a extra y shaped pipe to recirculate the air through the vents on the chimney pipe.

Im not sure I follow what you mean here?

ahernjohn

If your extractor is ducted out there is no need to use charcoal filters as these are only used to recirculate and clean the air when putting it back in the room.
If you are using proper grease filters and cleaning them regularly (most of them can be washed in a dishwasher) you should not have a problem with it clogging up your motor.
I have been fitting kitchens for 25 years and can tell you that raising or lowering the extractor will not make any difference as long as it has decent extraction and is working properly.