24V DC Centrifugal Fan for a Compact OEM Cooling Product

What the customer asked for

An OEM came to us already knowing what they wanted. Their enquiry named the model: our LWFD3G120-072SM-02 DC centrifugal fan.

They asked for the full specification sheet and a sample. In other words they had pre-qualified the DC centrifugal fan from published data, and were moving from paper to prototype.

One instruction stood out

The brief said plainly that no speed control was wanted. That is an unusual thing to write down, yet it was deliberate. A fixed-speed fan keeps integration simple. Moreover it strips out PWM or 0-10V hardware the product would never use.

The constraints

• A 24 VDC nominal rail, with the fan working anywhere from 16 to 28 VDC.
• Next, a fixed envelope of 188 by 99.5 by 188 mm, confirmed by the 3D STEP file they sent.
• Finally, both CE and ETL certification, so the end product could sell in Europe and North America.

That voltage window points at telecoms equipment, specialist vehicle HVAC or cabinet cooling. All three run off batteries that sag and chargers that surge. Consequently all three punish a fan that cannot cope.

Why this DC centrifugal fan fits

Because the customer named the model, our first job was documentation rather than design. So the approved specification sheet went out the same day the enquiry arrived.

Even so, the engineering interest lies in why that model suits the job.

No AC option, and no argument

A 24 VDC bus rules out an AC motor at once. Furthermore, adding an inverter would introduce a failure point, cost money and dump heat into an enclosure already being cooled.

Simple beat clever

We did look at a controllable fan from our SmartEC range. However, it was overkill here. The two-wire brushless motor in this DC centrifugal fan connects with a positive and a negative, and nothing else.

For a customer who explicitly does not want speed control, that is not a compromise. It is the correct answer, and it costs less.

Forward-curved, on purpose

Here the DC centrifugal fan uses a forward-curved impeller, which is a genuine trade-off rather than a default.

Forward-curved blades move more air from a small housing at low to moderate pressure. A backward-curved impeller is more efficient, yet it needs a larger diameter for the same volume. So when the envelope is fixed at 188mm, that difference decides the choice.

The impeller is PA66, so it stays light and quiet. Underneath it, a continuous duty motor on two ball bearings carries an L10 life of 40,000 hours.

Technical Specifications

Note the voltage range rather than the nominal figure. That window is what makes the fan usable on a real battery-backed rail.

Technical Documentation

LWFD3G120-072SM-02-14.pdf

Here the specification sheet contains the complete electrical and mechanical data, performance P-Q curve, and dimensional drawings an HVAC engineer needs to validate the fan’s integration into their system.

This product image provides a clear visual reference of the fan assembly, including its galvanized steel housing and forward-curved impeller, for use by procurement and assembly personnel.

Why the OEM stayed with us

Sometimes the value is not in the engineering at all. Instead it sits in how fast a supplier answers.

• Same-day response on standard products. This request arrived, was processed and was approved on one day. Design cycles stall waiting for datasheets, so removing that wait is worth more to an OEM than it sounds.
• Certification already done. The fan carries ETL for North America and CE for Europe. Consequently the customer avoided a validation program and the market access risk that comes with it.
• Component cost at volume. This DC centrifugal fan carries its performance and life ratings into a product that is built repeatedly. Where a component ships in volume its cost compounds, which is why in-house production matters more here than on a one-off.
• A route to customization later. Today they use a standard model. If a future version needs a different connector or bracket, our 90-day NPI cycle handles it, against the 12 to 18 months European makers typically quote.

Browse the centrifugal fan range, or the DC fan section. Safety testing follows UL 507.

Questions about this fan

What are the lead times for samples and production?

Samples of a standard DC centrifugal fan like this usually ship in 5 to 7 working days. Meanwhile make-to-order production of 100 to 500 units runs about 15 to 25 days. For larger volumes a frame agreement is worth setting up, since a forecast lets us hold stock against your schedule.

What happens outside the 16 to 28 VDC range?

Meanwhile the integrated controller protects the fan. Below 16V it shuts down rather than run unstably. Above 28V the over-voltage circuit cuts power to the electronics. Both are protective actions rather than failures. However, the 40,000-hour life rating only applies inside the stated range.

Does the ETL mark cover Canada as well as the USA?

Yes. The ETL Listed Mark on this model covers both national standards: UL 507 for electric fans and CSA C22.2 No. 113 for fans and ventilators. Consequently the fan can go into equipment for the whole North American market without separate approvals.

Why choose a forward-curved impeller when backward-curved is more efficient?

Because efficiency is not the only constraint. Backward-curved wins on power draw, though it needs more diameter for the same airflow. Where the housing size is fixed and pressures are moderate, forward-curved gives more air per millimetre of frame. Change the envelope and the answer changes with it.