Large AHU Centrifugal Fan with RS485 Control: 963 Pa Case Study

What the integrator asked for

The request arrived with one technical requirement attached. An OEM needed a large backward-curved AHU centrifugal fan, and it had to speak RS485.

That single word tells you a great deal. Integrators ask for RS485 when the fan must sit on a network. Namely a building management system, or an industrial SCADA setup. There, somebody wants speed control, monitoring and fault data from a screen rather than a switch.

Here the frame size confirmed the scale. A 630mm impeller means large air handling units, data center CRAH arrays, or industrial process work. In all of them, moving over 21,000 cubic meters an hour is routine.

• Three-phase supply anywhere between 380 and 480 VAC.
• A maximum of 963 Pa from the AHU centrifugal fan, to push through duct, HEPA banks and coils.
• CE compliance, since the target market demands it.
• Finally, reliable running from -30C to +40C.

The pressure figure explains why this fan exists. A HEPA bank alone can absorb several hundred pascals, and it worsens as the filter loads. Without headroom, therefore, airflow collapses long before anyone changes the filter.

Configuring the AHU centrifugal fan

Meanwhile the RS485 requirement pointed straight at our LWBE3G series, the third generation of our backward-curved platform. That platform handles high pressure at good efficiency. Nobody needed to invent anything, so the question was purely how to configure it.

Why not an AC motor and a VFD

We briefly weighed a standard AC motor with an external variable frequency drive. Then we rejected it.

A separate drive is another part for the OEM to buy, mount and wire. Moreover it takes panel space, it needs commissioning, and it is one more thing to fail in a plant room nobody visits often.

Why the integrated route is better

Instead we specified the AHU centrifugal fan with our SmartEC intelligent motor. That platform carries 0-10V, PWM and RS485 Modbus RTU on the motor control board itself.

Consequently the LWRS485-01 V2 protocol was a configuration step rather than an engineering project. The customer receives a factory-validated fan instead of a fan plus a drive they have to make work together.

What shipped in the end

The final model, LWBE3G630-188PT-07, pairs a 630mm aluminum alloy impeller with the SmartEC drive. We balance that impeller to G6.3, which keeps vibration and noise down on a wheel this size.

Here the whole assembly sits in a plug-fan frame, so it mounts straight into an AHU plenum. Meanwhile IP54 protection on the motor suits the indoor plant rooms these units live in.

Technical Specifications

The speed control row is the one that matters here. Otherwise this AHU centrifugal fan is a standard 630mm plug fan.

Technical Documentation

For detailed engineering review, the following documents were produced and approved for this project.

Technical Datasheet (PDF)
This is the final technical datasheet for the LWBE3G630-188PT-07, containing performance curves, dimensional drawings, and electrical specifications needed by design engineers for system integration.

The image shows the assembled EC backward-curved plug fan with its mounting bracket, providing procurement managers and installers a clear visual reference of the delivered product.

Why the integrator specified our platform

On a project like this, four things mattered.

• An approved specification in days. The customer needed documentation for a fan with a named control protocol. Our internal workflow turned that around quickly, where European suppliers commonly quote 12 to 18 months even for configuration work.
• Control that is part of the motor. SmartEC is not a bolt-on. Consequently Modbus works out of the box, which shortens BMS integration and removes the compatibility problems third-party controllers introduce.
• European-level engineering at a lower price. This 630mm AHU centrifugal fan performs on a par with top European brands, backed by testing to ISO 5801 and AMCA 210/211. Manufacturing in Ningbo, however, puts it materially below them on price. That gap decides tenders.
• A form factor built for arrays. A plug fan has no scroll housing, so it drops into a plenum and combines readily into a FanWall. Together with native RS485, that makes it a sensible building block for redundant, properly controlled air handling systems.

Browse our EC plug fan range, or the AHU fan section for array applications. The Modbus Organization publishes the protocol itself.

Questions about RS485 and arrays

What is the lead time for this configuration?

We draw and approve documents for a standard model with a named protocol within days. Afterwards, once your purchase order lands, production for a fan this size runs 15 to 30 days.

Is the RS485 implementation Modbus RTU?

Yes. The LWRS485-01 V2 option implements Modbus RTU, the usual standard in building automation and industrial control. A master BMS or PLC reads RPM and current, then writes speed commands. Furthermore we supply the full register map, so integration never becomes guesswork.

Can it be used in a FanWall array?

Yes, and we designed it for exactly that. A plug fan has no scroll housing, which is what makes plenum mounting and N+1 redundant arrays practical. Native RS485 then simplifies synchronising speeds and balancing load across every fan in the array.

What L10 life and bearings does it use?

We specify 40,000 hours L10 for continuous running at a 40C ambient, on maintenance-free deep groove ball bearings. Those bearings suit the dynamic loads a 630mm impeller creates, which run considerably higher than a small fan imposes.