493mm Axial Fan Impeller for an HVAC OEM: Case Study

What the OEM sent us

An established HVAC OEM wanted a replacement axial fan impeller. Initially the enquiry was about as lean as they come. Namely a photo of a rival part, a 12mm bore, and clockwise rotation.

Notably their aim was not a redesign. They wanted a second supplier, to cut parts cost and spread risk, without touching the product they already build.

However, the unstated constraints mattered as much as the stated ones.

• A 493mm outer diameter, since the housing fixes it.
• An overall depth of 144mm, likewise fixed.
• The same airflow as the current part, on their standard motor.
• Lastly, a full drawing rather than a spec sheet, for CAD fit checks.

That third point carries real weight. Blade pitch, curve and surface finish all change airflow and pressure. Consequently a part that measures the same can still behave differently. If the finished condenser runs hotter, the swap has failed.

Matching the axial fan impeller from stock tooling

The request was for one part rather than a whole fan. Consequently the work was matching shape and material, not designing a machine.

A match already in tooling

Our team checked the 493mm diameter, the 12mm bore and the rotation against our library of existing tooling. A direct match came back. Namely the LWF-ø493×143-03.

That is the best possible outcome here. Existing tooling means no NRE charge, and no wait for development.

Why three blades suit a condenser

Here the axial fan impeller has three blades, which is worth explaining.

A condenser moves a lot of air across a coil with little in the way, so pressure stays low. A three-blade wheel is very efficient there. It gives more airflow with less noise and less power than a five or seven-blade design.

More blades make more pressure. Here, though, that ability goes unused. Consequently it would be an over-built and dearer answer to a question nobody asked.

Choosing the polymer

Secondly, material was the other half of the review, since this model comes in several polymers.

We proposed reinforced AS, which balances UV resistance, stiffness and cost well outdoors. Meanwhile reinforced polypropylene was offered as an alternative, since it stands up better to chemical attack.

The deliverable itself was certainty. A dimensioned drawing from a proven mold removes every tooling doubt. Furthermore, it gives the customer exactly what their own checks need.

Technical Specifications

Note the material options row. One axial fan impeller shape comes in several polymers. The questions at the end explain when each earns its place.

Technical Documentation

Meanwhile the following documents were generated and approved as the final deliverables for this engineering project phase. They provide all necessary geometric and visual data for OEM integration.

LWF-ø493×143-03.pdf
This is the primary engineering deliverable, a dimensionally complete 2D manufacturing drawing required by the customer’s design engineers to verify fit and clearance within their product assembly.

Here the product image shows the final impeller geometry and finish, used by procurement and quality teams for visual confirmation and component identification.

Why component sourcing came here

When an OEM sources a single part, four things count.

• A production drawing in days. Meanwhile the customer needed a fast, accurate answer to a sparse enquiry. Our process returned an approved, production-ready manufacturing drawing quickly, which is what lets a sourcing decision happen.
• Tooling that already exists. Finding the LWF-ø493×143-03 mold removed tooling cost and wait time alike. Since we make impellers, motors and controllers, we bring part-level depth a distributor cannot.
• A measurable cost cut. Across thousands of units, buying direct from us rather than a European source saves real money on the parts list. Nothing is given up on engineering quality either.
• Material advice, not just part matching. The conversation covered polymer choice as well as dimensions. Recommending reinforced AS for UV stability, or PP for chemical exposure, is what optimises a component for its whole service life.

Browse our impeller and fan blade range, or the axial fan section for complete assemblies. Plastics testing methods are published by ASTM.

Questions about component supply

Can it be adapted for a different shaft or material?

Yes. The standard bore is 12mm. Other shaft sizes need either a different hub insert, or a small mold change. For a new material, such as glass-filled polypropylene for higher temperature or strength, we run a 90-day NPI to validate the material and produce samples.

What is the lead time on 1,000 units?

For an existing make-to-order axial fan impeller, 15 to 25 days from order confirmation to ex-works Ningbo. That is considerably faster than the 30 to 45 days a complex assembly such as an ATEX-certified fan requires.

Will this impeller give me 1200 m3/h at 45 Pa?

An axial fan impeller alone cannot answer that. Performance depends on the whole system. Namely this wheel, a specific motor at a specific speed, and the housing around it. For qualified OEM projects we run a system CFD simulation to predict the duty point accurately before anybody builds a prototype.

Why does surface finish matter on a molded impeller?

Because a rough blade trips the airflow into turbulence sooner than a smooth one. That costs efficiency, and it adds noise. On a second-source part it is a difference no caliper finds. Consequently it is a good reason to work from a drawing rather than from measurements.