12V DC Cross-Flow Fan Uprated to 125 m3/h with PWM Control

What the OEM needed changed

An OEM asked us for a 12V DC cross-flow fan for new equipment, working inside a 475mm installation length.

They had found a close match in our catalog already. However, the published datasheet showed 95 m3/h, and they needed 125 m3/h. It also used 0-10V analog control, whereas their board sends PWM.

Three changes, one envelope

• First, airflow had to rise by more than 30%, from 95 to 125 m3/h.
• Second, control had to change from 0-10V analog to PWM.
• Third, a protective grille had to be added, since operators can reach the outlet.
• Meanwhile none of that could alter the 474 by 50 by 53.3 mm body.

That last line is the hard one. Extra airflow usually costs space, and here there was none to spend.

Uprating the DC cross-flow fan without new hardware

We confirmed the platform first. This DC cross-flow fan already fitted the envelope on its 30mm impeller and 420mm length, so the frame was never in question.

Where the missing 30 m3/h was hiding

A new motor or a redesigned impeller would have solved it. Both were rejected, because either one triggers a full 90-day NPI cycle and adds cost the customer did not need to carry.

So the team looked at the 3725-series motor instead, and found headroom. The 95 m3/h figure on the baseline model was not a mechanical ceiling at all. It came from a software-limited speed profile.

Our engineers wrote a new control profile that runs the fan at its full rated 2400 RPM, which delivers the 125 m3/h target. All of that happened inside the SmartEC platform, with no new parts.

Changing the control interface

The 0-10V to PWM change was a straight swap of the control logic board. Because the platform is modular, that counts as a standard modification rather than a redesign.

The grille

Here the only genuine hardware work was the guard. We designed an aluminum protective grille, cut the tooling for it, and modified the iron side plates to carry the mounting points.

The finished DC cross-flow fan was validated at 125 m3/h with PWM control and the grille fitted. Consequently the whole job stayed inside a light development framework.

Technical Specifications

Meanwhile the current draw below is worth noting. In practice, running the same motor at full speed costs very little extra power.

Technical Documentation

The mechanical drawing provides the final approved dimensions, specifications, and bill of materials for the LWCD-30420LG-06-14. It is the primary document for system integrators and quality assurance teams.
Download Final Specification: LWCD-30420LG-06-14

For engineering reference, this document shows the baseline model LWCD-30420LN-06-00. It is useful for procurement managers comparing the final solution against the original component.
Download Baseline Specification: LWCD-30420LN-06-00

Product image shows the final assembly with the custom-fitted aluminum protective grille, confirming fulfillment of the safety requirement for design engineers.

Why the change took days, not months

This was a small project. Even so, it shows what happens to a modification when the supplier owns the platform.

• Platform changes move quickly. This DC cross-flow fan went from enquiry to an approved, documented solution in a fraction of the 12 to 18 months imported European brands typically need for a scope change of this kind.
• Firmware is cheaper than hardware. Delivering a 31% airflow increase through control logic rather than a new motor kept hardware cost flat. That is why the price landed materially below a new custom design from a European supplier.
• The grille was made here. Designing, tooling and manufacturing it in-house avoided the delays and quality arguments that come with an outside supplier for a one-off custom part.
• Control options are pre-validated. Because the SmartEC drive is modular, moving from 0-10V to PWM carried very little risk. The same platform also offers Modbus, so an OEM can vary control method across a product line without redesigning fans.

Browse the cross flow fan range, or the DC cross flow fan section. Airflow figures follow AMCA 210.

Questions about this modification

Can the airflow go higher than 125 m3/h?

Not on this combination. The 125 m3/h figure is the validated maximum for a 30mm impeller with the 3725 motor at 2400 RPM. Going further needs a bigger motor or a larger impeller, and both change the footprint. Consequently that becomes a full NPI project rather than a modification.

What is the lead time for a modified fan like this?

Production quantities of 100 to 500 units run 15 to 25 days once the final drawing and quotation are approved. Meanwhile the modification itself adds no time to the build, since the changes live in firmware, a control board and one tooled part.

Which other control inputs are available?

Several. The baseline used 0-10V analog and this build uses PWM. Meanwhile the same SmartEC platform supports RS485 for Modbus, simple on/off voltage control, or a custom scheme where an OEM system needs one.

Why was the standard model limited to 95 m3/h in the first place?

Because a published rating is a promise, not a maximum. The baseline profile leaves margin for noise, temperature rise and long-term life at the rated conditions. Running at full speed is entirely within the motor capability, though it does trade some of that quiet margin for airflow. Here the customer wanted the airflow.