AHU Centrifugal Blower for a 5000 m3/h Duty Point: Case Study

What the AHU integrator needed

A system integrator building commercial air handlers needed a centrifugal blower giving 5,000 m3/h at 270 Pa.

Notably they were specific about the type. Double inlet, forward curved, on an AC motor fed by 380V three-phase.

That AC preference is a choice rather than an oversight. It points at proven, low-cost technology, most likely paired with an external VFD for speed control.

• An impeller between 250mm and 280mm across.
• A formal spec sheet, backed by test data compliant with ISO 5801.
• Then a single-speed build, rather than a switchable one.
• Lastly, a fast turnaround, since the timeline was tight.

The underlying need is simple. They have a target, and they want to get from concept to a tested, production-ready part without a long wait.

Matching the centrifugal blower to the duty point

Five thousand cubic meters an hour at 270 Pa is a common duty point in mid-size commercial HVAC. Consequently the work was matching rather than inventing.

Respecting the AC request

An EC version with SmartEC controls gives better efficiency and built-in speed control. However, the customer asked for AC explicitly.

Read properly, that signals a design built for cost and paired with an external drive. Consequently the search moved to our DD and DDM series of direct-drive centrifugal blowers.

Forward-curved, for size and noise

Secondly, blade shape came next. At middling pressure and high volume, forward-curved blades win on size and on noise.

They move plenty of air from a smaller, quieter and cheaper unit than a backward-curved wheel needs. Backward-curved earns its place once pressure climbs. At 270 Pa, though, it has not.

The model that matched

Meanwhile, checking the duty point against our database pointed at the DDM 10-10 size class, a double-inlet forward-curved fan with a 10-inch wheel.

So we proposed the DD10-10I-014. Its measured P-Q data, from our AMCA 210/211 compliant lab, shows 4,988 m3/h at 264.78 Pa on 1,745.8W. Against a 5,000 m3/h and 270 Pa target, that is about as close as selection gets.

Single speed from a multi-tap motor

Finally, the customer wanted one fixed speed. Our standard motor is multi-tap, which sounds like a mismatch. In fact it is not.

We simply sent wiring instructions to connect the high-speed winding alone. That meets the need with a standard part, so no NPI delay and no development cost follow.

Technical Specifications

Here the maximum figures below sit above the duty point this centrifugal blower was picked for. That gap is the margin an AHU designer needs as filters load.

Technical Documentation

The following documents were generated to support the customer’s design-in process.

DD10-10I-014 Specification Sheet
This is the final approved specification sheet, providing comprehensive performance data, P-Q curves, and compliance information needed by both procurement and engineering.

DD10-10I-014 Engineering Drawing
This is the master engineering drawing with critical dimensions, wiring, and initial specifications, used by design engineers for fitment checks.


The image shows the initial technical exchange, capturing the customer’s core performance requirements and the internal engineering recommendation.

Why the integrator qualified us

On a tight timeline, four things counted.

• A documented answer inside 48 hours. The job ran from first query to a fully documented, tested answer in under two days. That speed applies even to standard product picks, where larger European rivals often take weeks.
• The right technology, not the newest. Hearing the AC request, and picking a solid AC answer, met the target well below an over-specified EC fan. In turn that feeds straight into the OEM bill of materials.
• Data you can design against. Full P-Q, power and current tables come from testing to AMCA 210/211 and ISO 5801. Consequently their engineers designed the fan in without padding for doubt.
• A second source with no redesign. Our DD and DDM centrifugal blower series matches widely used European models on both dimensions and output. Consequently an OEM qualifies us as a second source with no mechanical or electrical rework.

Browse our centrifugal blower range, or the AHU fan section. Fan testing is defined in ISO 5801.

Questions during selection

Can the speed be controlled?

Yes, with an external variable frequency drive, which is what this AC centrifugal blower expects. The standard motor also has multiple winding taps for step-speed control, though a VFD gives better energy savings and finer tuning. For integrated control instead, look at our SmartEC series.

What certifications does it hold?

Full CE marking, confirming compliance with the European LVD and EMC directives including EN 60335-1, plus RoHS and REACH. That suits equipment bound for the EU. UL certification is available on other models for North America.

What is the lead time?

Engineering samples of a standard configuration are usually available within 7 to 10 days. Production orders up to 500 units follow a make-to-order lead time of 15 to 25 days from purchase order confirmation.

Why does a double-inlet fan suit an AHU?

Because it draws air from both sides of the wheel, which roughly doubles the capacity of a given diameter. In an AHU the cabinet usually has width to spare and very little height. Consequently gaining capacity along the axis, rather than the diameter, is exactly the trade you want.