Retrofit a 450mm AC Centrifugal Fan for 70°C Heat

Thermal Limits on Industrial Exhaust Systems

The customer had a severe thermal problem. First, they needed a 450mm AC centrifugal fan to hit exactly 4500 m³/h at 200 Pa static pressure. Next, the equipment lived in an environment pushing 70°C ambient heat. At this extreme temperature, their original FLH450/90A-1860A2 unit failed quickly.

So, they needed a new fan that could last 20,000 hours in this heat. Also, the machine required a standard 230V 50Hz power supply. Space was very tight. The new rotor had to fit a 454mm mounting hole.

In addition, the maximum depth was only 251mm. Finally, the customer required CE compliance and performance tested to ISO 5801 methods. A 70°C operating limit is very harsh. Standard commercial blowers die quickly in these conditions.

Therefore, we had to change the internal materials to protect the 450mm AC centrifugal fan. The system was a high-heat industrial process. The old fan could not handle the thermal stress. As the internal cabinet heated up, the old motor windings degraded.

First, the grease would leak out. Then, the bearings would lock up. So, replacing it with the exact same model was useless. Instead, the customer asked us to engineer a drop-in replacement.

We had to match the physical size perfectly. But we needed to greatly improve the heat resistance. We tested all parameters to ISO 5801 methods.

Engineering the High-Temperature Assembly

We reviewed the original FLH450/90A-1860A2 performance data. We had to match the airflow while surviving extreme heat. Therefore, we tested several rotor setups for this project.

Choosing the 450mm AC centrifugal fan Technology

First, we looked at motor options for this 450mm AC centrifugal fan. We immediately rejected an EC motor retrofit. EC motors have great efficiency. However, their internal electronics break down rapidly above 60°C.

So, we chose a rugged 4-pole external rotor AC motor. It handles raw heat much better. Next, we focused on the electrical insulation. To protect the motor, we applied Class F insulation.

This keeps the stator windings from melting. Then, we fixed the bearing issue. Standard motor grease turns to liquid at 70°C. When grease leaks, bearings seize.

Therefore, we used SKF maintenance-free deep groove ball bearings. These use special high-temperature grease. This choice increased the unit cost materially. Even so, it was the only way to reach the lifespan goal.

We calculated a 30,000-hour L10 life at 40°C. This gave the customer their needed 20,000 hours at 70°C.

Selecting the Impeller Material

Next, we looked at the blade material. Plastic blades warp easily in 70°C heat. Warped blades ruin the fan balance and cause extreme vibration. Instead, we used a backward-curved aluminum alloy impeller.

Aluminum is heavy. It adds rotational mass to the fan. So, we balanced the rotor to G6.3 standards to keep vibration low. The heavier metal requires more electrical power to spin.

Our final LWBA4E450-138NS-14-00 model draws 860 W at full load. It pulls 3.5 A of current at 230V. Despite the higher power draw, it easily clears the target. In fact, it pushes up to 6549 m³/h and reaches 505 Pa.

The aerodynamic trade-off for this metal blade is noise. The peak noise level hits 78 dB(A). However, we accepted this trade-off for the thermal reliability.

Managing the Physical Space Constraints

We also had to fit the heavier motor into a small space. The cabinet depth was restricted to 251mm. First, we measured the old FLH450/90A-1860A2 frame. Then, we designed a custom backplate to hold the aluminum impeller.

This kept the new fan inside the 454mm envelope. Also, the heavier rotor meant the start-up torque was higher. We tested the start-up sequence to ensure the 230V supply could handle the 3.5 A load. Finally, the IP54 rating protects the hot motor from industrial dust. This keeps the SKF bearings clean and extends their operating life.

Technical Specifications

The extreme heat shaped this specific build. By contrast, the raw airflow gives a large safety margin above the 4500 m³/h requirement. Therefore, the Class F insulation and SKF bearings are the most vital parts here. They keep the system running smoothly. Also, the IP54 rating protects the motor from dust.

Reference: AMCA 210 covers the test method behind these figures.

Technical Documentation

Longwell Approved Technical Specification contains the finalized P-Q curve, dimensions, and wiring data.
Customer Original Specification shows the original FLH450/90A-1860A2 data we had to beat.
This chart shows the lifespan loss at extreme ambient temperatures.
This graph maps the L10 bearing life against the mounting angle.

Specifying Fans for Extreme Ambient Heat

If you need a 450mm AC centrifugal fan for high-temperature exhaust, review these details first.

• First, measure the true air temperature exactly at the fan inlet. Room temperature is not enough. Internal cabinet pockets easily hit 70°C under load.
• Next, check the bearing grease specs. Standard bearings lock up completely above 60°C. You must ask for high-temperature hardware like SKF bearings.
• Also, avoid plastic impellers if the air exceeds 55°C. Metal blades cost more and weigh more. Even so, they stop sudden failures from melted plastic.
• Finally, send your exact hole dimensions to the factory. Because we manufacture the impeller, we can adjust the backplate. This ensures the fan fits your machine perfectly.

Related: Centrifugal Fans.

Common Questions on 450mm AC Centrifugal Fan Retrofits

Browse our centrifugal fans range, the backward-curved fans section, or forward-curved fans.