ECOFIT Constant Airflow Fan

In comfort and tertiary HVAC installations, controlling airflow is of great importance in order to maintain the operating point defined during the system design phase. Some applications require a stable airflow rate.

The ECOFIT constant airflow fan, equipped with an EC (Electronically Commutated) motor, meets this requirement.

What is a constant airflow fan?

A constant airflow fan is a system capable of maintaining a stable airflow rate (m³/h) even when the conditions of the ventilation network change.

With a conventional fan, the air volume varies according to pressure drop. As soon as a filter becomes clogged or a damper closes, resistance to airflow increases, leading to a decrease in airflow.

With constant airflow control, the fan automatically adjusts its speed to compensate for these variations and guarantee the desired air volume.

Understanding pressure drop in a ventilation network

Pressure drop (ΔP) corresponds to the pressure decrease experienced by air as it flows through an installation.

It is generated by:

• duct lengths,
• duct cross-sections,
• bends and reductions,
• grilles and dampers,
• filters (whose pressure drop increases as they become clogged),
• equipment installed in the airstream (coils, heat exchangers, etc.).

The greater the pressure drop, the more pressure the fan must generate to maintain the same airflow.

Without regulation, this generally results in a gradual decrease in airflow.

How does EC technology enable constant airflow?

Modern fans equipped with EC (Electronically Commutated) motors are particularly well suited for maintaining constant airflow.

1. Precise speed control

The EC motor is a brushless motor with integrated electronics. Unlike traditional fixed-speed AC motors, it allows continuous and precise adjustment of rotational speed. Integrated software in our single-inlet and double-inlet forward-curved centrifugal fans enables speed control without the need for an additional control box. For our backward-curved centrifugal fans, speed control is achieved by adding a control box and a pressure tapping inlet cone.

This adjustment capability is essential to compensate for variations in pressure drop.

2. Automatic control loop (with control box for backward-curved centrifugal fans)

The system operates according to a control loop:

A sensor (differential pressure or airflow) measures the actual condition.

The controller compares the measured value with the setpoint.

If airflow decreases, the fan speed increases.

If resistance decreases, the fan slows down.

This regulation can be controlled via a 0–10 V or PWM signal.

3. Optimized energy efficiency

EC motors offer high efficiency. The fan never runs faster than necessary, making it possible to combine airflow stability with energy optimization.

In which applications is constant airflow recommended?

The constant airflow fan is particularly relevant when the required airflow is fixed, but pressure drop changes over time.

Ventilation with filtration

In air handling units or filter boxes, the progressive clogging of filters increases pressure drop. Constant airflow control maintains aerodynamic performance up to the filter replacement threshold.

Cleanrooms and laboratories

Sensitive environments require precise and constant air renewal (the constant pressure function is also suitable for this type of application).

Constant pressure networks

In some installations, the objective is to stabilize pressure rather than overall airflow. In such cases, constant pressure control may be preferable. This function is also available on our forward-curved and backward-curved fans.

The choice between constant airflow, constant pressure, and variable airflow depends on the primary objective of the installation.

To help you make the right choice, our team supports you in analyzing and sizing your ventilation system — feel free to contact us from the early project stage.