48V DC Centrifugal Fan for HVAC OEM: 798 Pa Case Study

What the OEM was matching

An HVAC OEM was qualifying a second source for a critical part, wanting steadier supply and lower cost. They needed a 48V DC centrifugal fan making at least 765 Pa of static pressure.

Usefully, they sent the full spec for the existing part rather than a vague note. Consequently that datasheet became the benchmark for output and for fit alike.

• A 48 VDC rail, since supply may wander from 36 to 57V.
• Maximum airflow of 1504 m3/h at the very least.
• A 250mm impeller on the existing M4 pattern, because the chassis cannot change.
• 0-10VDC or PWM control, matching the signal they already send.
• No more than 71 dB(A), measured as before.
• Lastly, a range from -25C to +60C, plus CE certification.

One phrase governs this project. No change to the chassis. Basically, a second source needing sheet metal work is not a second source, since the whole point is switching without a project behind it.

Finding an equivalent DC centrifugal fan

Our engineers began with an equivalency study, mapping the old fan performance curve, its drawings and its electrical interface.

Throughout, the aim was a standard product that meets or beats the requirement, without opening a custom NPI cycle.

Two better options we rejected

We looked at a smaller 225mm platform first. It cannot make 765 Pa at sensible efficiency, so it went no further.

More interestingly, we also modeled a stronger motor on the 250mm frame, then discarded it. It works, yet it draws 220W against a 192W budget.

That overage sounds trivial, and it is not. Going past the power budget forces a change to the supply in the end system. That is exactly the redesign the customer wanted to avoid. In short, being better is not the same as dropping in.

The fan that matched

The answer was the LWBD3G250-092NH-14-00 DC centrifugal fan.

Its 250mm impeller, die-cast aluminum housing and mounting points match the benchmark exactly. Consequently nothing about fitting it changes. Power draw is 192W at 48 VDC, right on budget, and the built-in SmartEC controller takes the same 0-10V and PWM signals.

Where it does better

Meanwhile it gives 1549 m3/h and 798 Pa. That is roughly 3% more air and 4% more pressure than the part it replaces.

Crucially, it does that at the same 71 dB(A). Extra output bought with extra noise would not pass. On a drop-in replacement, somebody notices immediately.

Technical Specifications

Compare the airflow and pressure rows against the benchmark in the text. The margin is small on purpose, since this DC centrifugal fan had to be an exact substitute.

Technical Documentation

Here the following documents were generated and approved during the project lifecycle. They represent the final deliverables confirmed by the customer.

Longwell Solution Spec Sheet: This is the final approved specification sheet for the Longwell fan, which an engineer would use for system integration.
View LWBD3G250-092NH-14-00 Spec Sheet (PDF)

Original Requirement Document: The original competitor technical specification submitted by the client, which served as the engineering baseline for this project.
View Competitor Benchmark Spec Sheet (PDF)

Source Document (DOCX): The editable source file for the Longwell spec sheet, useful for procurement teams who may need to copy data into their ERP systems.
Get LWBD3G250-092NH-14-00 Spec Sheet (DOCX)

Why the second source qualified here

While the customer qualified an alternative, three things counted.

• Equivalency analysis inside 48 hours. Given a competitor part number, our team returned a complete proposal with verified performance curves and dimensional drawings within two days. That is a standard service, and it lets procurement decide quickly.
• A performance upgrade with no redesign. This DC centrifugal fan drops in mechanically and electrically, so no re-tooling cost arises anywhere in the customer product. The extra performance was measured on a bench, not projected from a calculation.
• Samples from stock. With yearly output above 120,000 data center cooling units and 30,000 cold chain units, supply is not the limit. Evaluation samples went out from existing stock. Consequently their validation ran in weeks rather than months.

Browse our backward-curved centrifugal fan range, or the DC cooling fan section. Protection ratings are defined in IEC 60529.

Questions during qualification

Is it genuinely a drop-in replacement?

Yes. The mounting pattern of four M4 fixings on a 255mm circle, the 250mm impeller and the 99.5mm overall depth are mechanically identical. Electrically it matches too, with 48V, ground, 0-10V or PWM control and an FG signal on a standard connector. No mechanical or electrical change is required.

What is the lead time in production quantities?

Make-to-order runs of 100 to 500 units take 15 to 25 days. Sample and evaluation orders often ship in 1 to 5 days where stock allows. A frame agreement secures forecast-based delivery for larger annual volumes.

How is speed controlled and monitored?

Through our SmartEC electronics. Every DC centrifugal fan here takes either an analog 0-10V signal or PWM between 1 and 10 kHz on the control wire. A tachometer output on a separate wire returns four pulses per revolution, so your controller can track actual speed rather than assume it.

Why refuse the higher-power option that performed better?

Because a second source must fit the system that already exists. Drawing 220W against a 192W budget means changing the power supply, or else accepting a marginal design. Either way it costs more than the fan saves. Consequently the higher-performing option is the wrong answer here.