Commercial Box Fans

Frequently asked questions

What is a commercial box fan?

A centrifugal or mixed flow impeller in a rectangular steel casing, usually acoustically lined, with round duct spigots on the inlet and outlet so it fits straight into the duct run. Box fans deliver good airflow against the resistance of ducts, grilles and filters in a compact footprint that fits in ceiling voids, risers and plant rooms.

Is this the same as a domestic box fan?

No. A domestic box fan is a portable fan that stands on the floor or in a window to cool a room. A commercial box fan is fixed into ductwork and drives a whole ventilation system. If you are looking for a portable cooling fan, this is not the right range.

Centrifugal or mixed flow box fan?

Centrifugal box fans, such as the Systemair KVK, Elta Singleflow, Twinflow and Qube, cope well with higher system resistance from long duct runs, filters and attenuators. Mixed flow box fans, such as the Elta Multiflow SMB, move more air for their size on lower resistance systems. If the system has a lot of ductwork or filtration, start with a centrifugal fan. For a straight inline mixed flow duct fan, see our in-line fans.

Which box fans fit a shallow ceiling void?

Low profile ranges are built for this: the Systemair KVK Slim, the Vent-Axia Slimpak and the Elta Hideaway. Each product page lists the casing height, so check it against the void depth, and allow room for the duct connections and access to the terminal box.

What is a twin box fan?

A twin fan, such as the Systemair KVK Duo or KV DUO, has two fans in one casing set up as run and standby. If the duty fan fails, the standby fan takes over, so ventilation keeps running. It suits systems that must not stop, such as commercial toilets and plant rooms. See our twin fans.

AC or EC box fan?

AC fans are the lower cost option and are speed controlled with a stepped or electronic controller. EC fans use less energy, especially at reduced speed, run quieter when turned down and are fully variable through a 0-10V signal, which makes them easy to link to a BMS, timer or sensor. Use the buttons below to filter by motor.

Single phase or three phase?

Most small and mid size box fans run from a standard 230V single phase supply. The larger sizes and higher duty models are often three phase. Use the buttons below to filter by supply, and check what is available at the fan position before choosing.

Can box fans be used for kitchen extract?

Standard box fans are for clean or lightly contaminated air. For hot or greasy kitchen extract, use a fan rated for it, such as the Elta Qube SQUHT, rated for extract air up to 120°C, with grease filtration at the canopy. See our high temperature fans and commercial kitchen extractor fans.

How do I size a commercial box fan?

Work out the airflow the space needs, in m³/h or l/s, then add up the resistance of the system: ductwork, bends, grilles, filters and any attenuators or heat recovery. The fan needs to deliver that airflow at that pressure, which you can check against the fan curve in the datasheet linked from each product page. Send us the airflow and a sketch of the duct run and we will select a fan.

Are box fans speed controllable?

Yes. AC fans need a controller rated for the fan's full load current, and EC fans take a 0-10V signal or a potentiometer. See our speed controllers, or tell us the fan and we will match one.