Custom 230V AC Forward Centrifugal Fan Replacement: 250 m³/h

What the customer asked for

250 m³/h at 2450 RPM was the baseline airflow requirement presented by an OEM needing a direct drop-in replacement for a legacy forward-curved centrifugal blower. The original unit, a BVN BDRS 125-50 I, was failing to meet supply chain reliability standards, prompting the client to seek a localized manufacturing partner capable of matching exact flange and housing dimensions. We received the technical brief under project code LW2607272110, outlining a rigid set of mechanical constraints. The installation envelope was strictly capped at 170 mm in total depth and 180 mm in height, with a 72 mm by 77 mm exhaust flange interface. Mounting hole spacing required a precise 86 mm by 88 mm pattern using 5 mm diameter holes to align with the customer’s existing sheet metal bulkheads.

Electrically, the system operates on a standard European 230V, 50Hz AC grid, drawing 0.35 A with an 80 W input power limit. The motor required Class B insulation and an IP44 protection rating to survive the environmental conditions of the target application. The client projected a pilot annual demand of 150 units. They required a complete quotation covering per-unit cost and custom tooling fees to stamp the exact sheet metal housing. Any deviation in the physical dimensions, such as the 128 mm inlet ring diameter or the 94 mm motor protrusion, would cause interference in their assembly line.

How we answered it: choosing the ac forward centrifugal fan

Designing a custom AC forward-curved centrifugal fan to match an existing competitor’s footprint required tight mechanical tolerances and precise motor matching. We initially considered migrating the client to a highly efficient EC motor to reduce the 80 W power draw. That approach was rejected. An EC motor would require modifications to the customer’s existing AC control circuitry and negate the core objective of a fast, zero-modification mechanical and electrical replacement. We proceeded with a single-phase AC external rotor motor matched directly to the 230V/50Hz supply.

The engineering team focused heavily on the scroll housing geometry. Because the customer required a bespoke stamping die to replicate the exact 170 x 180 x 94 mm envelope, our mechanical engineers digitized the competitor’s 2D drawings into 3D CAD to evaluate the airflow path. We matched the 125 mm impeller diameter and 50 mm blade width to hit the 250 m³/h airflow target at 2450 RPM. The impeller was constructed from galvanized sheet steel for durability. The scroll housing was stamped from cold-rolled steel and treated with a black powder-coated finish to prevent corrosion. To meet the IP44 protection requirement specified on the original nameplate, we specified sealed ball bearings and enclosed the electrical connections, upgrading from the IP X0 base rating shown on some legacy technical drawings. Insulation Class B materials were selected for the motor windings to safely handle internal temperatures during continuous duty cycles. We absorbed the 90-day custom NPI cycle to design, tool, and stamp the exact flange dimensions. Specifically, we replicated the 62 mm by 66 mm internal exhaust opening, ensuring the new Longwell fan would bolt directly onto the customer’s existing equipment without a single millimeter of offset.

Delivered specification

Matching the 80 W input power and 0.35 A current draw ensures the customer’s existing relay and fuse sizing remains perfectly valid. The IP44 rating combined with Class B insulation provides sufficient thermal and environmental headroom for continuous commercial ventilation duty.

Every figure above comes from our own test chamber, measured using AMCA 210/211 and ISO 5801 methods. The published procedures behind those numbers are available from AMCA. As always, confirm the duty point against the finished unit before release, since installation conditions move it.

Drawings and datasheets

Dimensions table detailing the required flange and housing mounting measurements for the custom tooling process.

Reference photo of the target forward-curved centrifugal blower showing the required black metal scroll housing and wire mesh inlet guard.

Mechanical drawing specifying the precise physical layout, including the 170 mm by 180 mm overall footprint necessary for direct OEM integration.

Original motor nameplate confirming the 230V, 50Hz, 80W electrical parameters and the critical 250 m³/h airflow performance target.

Why this one came to Longwell

• Custom Tooling Cost Efficiency: For pilot batches of 150 units annually, European manufacturers frequently reject custom stamping requests or charge prohibitive non-recurring engineering fees. Longwell’s integrated tooling capabilities allowed us to quote an accessible molding fee for the bespoke sheet metal housing.
• Aggressive NPI Timeline: We completed this custom design cycle in our standard 90-day window, preventing OEM assembly line downtime and significantly outpacing the 12 to 18-month timelines typical of imported European brands.
• Price Point Advantage: By manufacturing locally in Ningbo under strict ISO 9001 controls, we delivered a unit cost materially lower than the incumbent brand while maintaining mechanical parity.
• In-House Aerodynamic Verification: Airflow characteristics were validated in our AMCA 210/211 and ISO 5801 verified independent laboratory, guaranteeing the final unit hit the strict 250 m³/h requirement before shipping.

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Questions the customer asked

Q: Can Longwell reverse-engineer and match existing competitor flanges exactly?

A: Yes. For project LW2607272110, we designed a custom stamping die to precisely replicate an 86 x 88 mm mounting hole pattern and a 62 x 66 mm exhaust opening. This ensured a zero-modification drop-in mechanical replacement for the OEM assembly line.

Q: What is the minimum annual volume required to justify custom sheet metal tooling for an AC centrifugal fan?

A: While higher volumes amortize tooling costs faster, our internal die-making capabilities allow us to support pilot production runs. We successfully executed this project based on a forecasted annual demand of just 150 units while maintaining highly competitive custom NPI molding fees.

Q: Does matching a legacy AC fan design affect delivery times compared to local European suppliers?

A: No. Our localized Ningbo supply chain allows us to complete custom new product introductions within 90 days. We maintain full internal control over metal stamping, motor winding, and assembly processes to prevent delays.