Extractor cooker hood efficiency

[Will2]

I am about to fit a cooker hood with extractor. The vent is some 12 feet from the hood; one bend only. Can someone tell me what capacity (cubic metres per hour) of fan would be required to "blow" that distance?

Thanks in anticipation

Will2

 

[ian]

The last cooker hood i fitted, the pipe had not to run further than 3 meters. does it not mention in the instructions.

 

[Marvo]

Usually you would work this out the other way around. You calculate the volume of air you need to extract either by referring to council regswhich will give you min requirements in room changes/hour or you look at the face area of the hood and the velocity required and get you volume from there.

Once you have your required volume you need to work out your system static pressure at that volume and specify a fan that is on-curve for those figures. The other considerations that might affect your choice of fan are the noise figures, the physical size, the energy consumption, whether it's speed controllable, does it need 'ex' rating or special high ambient temperature requirements etc.

If you're unsure about specifying fans then approach a respectable wholesaler with the specs of your system and they'll be happy to offer you some options.