What commercial extractor fan installation involves
The fan is the engine of an extraction system, and choosing one is not a matter of diameter or of fitting the biggest unit the space allows. A fan is selected against a duty point: a volume of air delivered against the resistance of the canopy, filters, ductwork and discharge. A fan picked without that calculation either under-delivers or runs noisily and inefficiently, a long way from its best operating point.
We supply the main kitchen-rated types. Centrifugal box fans with backward-curved impellers develop high pressure quietly and suit long duct runs and systems with odour control. Bifurcated axial fans keep the motor in a separate compartment, out of the airstream, for hot and grease-laden air. Mixed-flow in-line fans are compact where space is tight. We also supply roof-mounted vertical-discharge units and supply-air fans. For kitchen extract we specify fans with the motor out of the airstream, or rated for it, as DW/172 recommends.
Installation matters as much as selection. Fans are fitted on anti-vibration mounts with flexible duct connections so vibration does not travel into the ductwork or the building. They are positioned for maintenance access, weatherproofed where external, and wired through a local isolator in line with BS 7671.
Speed control is where the running-cost savings are. EC motors with integral speed control, or inverter drives on AC motors, let the fan turn down in quiet periods. Because fan power falls with the cube of speed, running at 80% speed uses roughly half the energy.
Choosing the right commercial kitchen extractor fan
Six things decide it: the airflow required, the system resistance, the air temperature, the noise limit at the nearest window, the space available, and whether the supply is single-phase or three-phase. We do the calculation and present options with their fan curves, so you can see where each one operates rather than taking a catalogue guess on trust.
If you already have a fan that has failed or is no longer adequate, see extractor fan repairs and extractor fan replacements.