Axial Fans

Frequently asked questions

What is an axial fan?

An axial fan uses a motor to spin an impeller inside a frame or case. The blades draw air in and discharge it along the same parallel axis as the shaft, in a straight line through the fan. That straight-through path is what gives axial fans their high airflow and low power draw, and it is also why they lose performance quickly once system resistance climbs.

Which type of axial fan do I need?

Plate axial fans mount on a square steel plate and sit in a wall or partition, discharging straight through. They are the standard answer for through-wall extract in workshops, plant rooms and warehouses. Cased axial fans sit inside a cylindrical case that connects to ductwork on both sides, so they fit into a duct run rather than a wall. Short cased suits general extract; long cased handles higher pressure and takes accessories like silencers and guards. Duct mounted axial fans are the smaller in-line units that sit within round ducting to boost airflow along a run. Roof fans mount on a kerb or upstand and discharge at roof level, used where there is no suitable external wall. Bifurcated fans house the motor outside the airstream, for hot or contaminated air.

Axial fan or centrifugal fan?

Pick an axial fan when you need volume and the system resistance is low to moderate: short duct runs, through-wall extract, general ventilation. Pick a centrifugal or mixed flow fan when the ductwork is long or complex, or where filters, silencers and bends push the static pressure up. Axial fans lose airflow steeply as pressure rises, so a fan that looks right on free-air figures can badly underperform once it is in a real system. If you are unsure, send us the duct layout and we will check the duty point.

What size axial fan do I need?

Size from two numbers: the airflow you need, and the resistance the system puts in the way. Airflow comes from the room volume and the air change rate the application calls for. Resistance comes from duct length, diameter, bends, grilles, louvres and any filters or silencers. Match the fan to the duty point where those two meet, not to the headline free-air figure on the datasheet. Where the calculation is marginal, size up and run the fan through a speed controller rather than running a smaller fan flat out.

Are axial fans speed controllable?

Yes. AC models run on electronic or transformer speed controllers, and three phase units generally need a transformer controller or an inverter. EC models have speed control built in and take a 0 to 10V signal or a potentiometer, which is why they are usually the better choice where the fan runs continuously. Running an oversized fan at reduced speed is quieter and cheaper than running a smaller fan at full duty. See our fan speed controllers, and check the controller matches the motor type, because AC and EC need different control.

Single phase or three phase?

Smaller axial fans are single phase 230V. Larger cased and plate axials from roughly 450mm upward are commonly available in three phase 400V, which is more efficient and easier to control at higher powers. Check what supply is available at the fan position before ordering, since converting later is expensive and it is one of the most common reasons an order gets changed after delivery.

Can axial fans handle high temperature or grease?

Not a standard one. Standard axial fans are rated for normal ambient air, and running one on a hot or grease-laden duty will shorten its life or fail it outright. For hot air streams see our high temperature fans, rated to run continuously at 120°C. Where the motor must stay out of the airstream entirely, a bifurcated fan is the correct design: we stock the Elta Biflow range from 250mm to 630mm in conical and cylindrical cases, listed on this page and on our commercial kitchen extractor fans page. Do not run a standard axial fan on a commercial kitchen grease extract duty.

What is the difference between AC and EC axial fans?

An AC fan runs at a fixed speed unless you add an external controller. An EC fan has the speed control electronics built into the motor, so it takes a 0 to 10V signal directly and runs at any speed you set without a separate controller. EC is typically 30% or more efficient across the operating range, soft starts, and is the usual specification on new commercial projects where energy performance is assessed. AC remains cheaper up front and is fine where the fan runs at one speed or only occasionally.

Do you supply axial fans for trade and project work?

Yes. We supply M&E contractors, installers, facilities teams and specifiers, and we hold stock across the main plate and cased ranges for next day delivery. If you have a schedule, a drawing or a duty list, send it over and we will price the lot, confirm phase and handing where it matters, and quote any controllers, guards or silencers alongside. Call 0161 399 3825 or email hello@efans.co.uk.