The original ebm-papst fan is no longer available.The model number is discontinued.The nameplate is damaged.Or your supplier simply says: “No stock.”......

So you start looking for a replacement.You find a fan with the same diameter and similar airflow. It looks like a perfect match.

But is it?Not necessarily. A proper fan replacement is not a model-number match.It is a system-performance match.

Start With the Operating Point

The two most important parameters are:Airflow + Static Pressure

For example:10,000 m³/h @ 300 Pa is completely different from:10,000 m³/h @ 800 Pa.

Even though the airflow is identical.The replacement fan needs to operate at the required airflow and system pressure, not simply deliver a similar maximum airflow.

Pic.1 Air Flow - Static Pressure Characteristics

This is why the system resistance and actual operating point should be considered before selecting a replacement.

Check the Electrical Parameters

Before selecting a replacement, confirm:

For example, a 400 V / 50 Hz three-phase fan cannot automatically be replaced by a 230 V single-phase model just because the dimensions are similar.Electrical compatibility comes before installation.

Pic.2 You can check these on the fan nameplate

Don't Forget the Control Signal

For EC fans especially, check how the original fan is controlled:

A replacement may provide the required airflow but still fail to integrate with the existing BMS or controller.Performance compatibility ≠ control compatibility.

Pic.3 Differences between PWM/0-10V/Modbus speed control、

Then Check Mechanical Compatibility

Once the performance and electrical requirements are clear, check whether the fan can actually fit.Important details include:

A fan that performs perfectly on paper is useless if it cannot be installed without major modifications.

Pic.4 Fan installation dimension drawing

Consider the Application Environment

The same fan may perform very differently depending on where it is installed.

For example:

AHU retrofit:Airflow, static pressure, dimensions and control integration are critical.

Dry cooler / condenser:Airflow, pressure, outdoor temperature, corrosion protection and noise may be more important.

Data center cooling:Reliability, controllability, acoustic performance and continuous operation become key considerations.

So don't ask only:“Which fan has the same size?”Ask:“Which fan can deliver the required performance under the actual system conditions?”

What If You Don't Know the Original Model?

This is actually quite common.

You may not have the original data sheet or even a readable model number.That's not necessarily a problem.Start with what you can collect:

Fan nameplate + airflow + static pressure + voltage/frequency + control method + dimensions + application photos

With these parameters, a suitable replacement can often be evaluated even when the original model is unavailable.

A Simple Replacement Checklist

Before selecting a replacement fan, confirm:

① Airflow