In mechanical ventilation systems with heat recovery used in residential and small commercial buildings, key features include a compact design, energy efficiency, quiet operation, and stable airflow. That’s why centrifugal fans with forward-curved blades (F3P – forward curved) are more commonly used in these applications, proving to be a better choice in many aspects than fans with backward-curved blades (B3P – backward curved).
What distinguishes F3P fans from B3P fans?
F3P fans have a steep pressure-to-capacity curve, meaning they can generate high compression at low airflows. This makes them ideal for small heat recovery units, where overcoming filter, heat exchanger, and system resistance while keeping energy use low is essential. Although their overall efficiency might be lower than that of B3P fans, it still works well for low airflows, especially since the F3P meets the required parameters at much lower speeds.
A lower rotational speed also results in significantly quieter operation. Thanks to the larger number of smaller blades and gentle flow turbulence, F3P fans produce less noise and vibration, which is essential for systems installed in single-family homes and apartments. Compared to B3P fans, which can be louder at low flow rates, F3P fans offer a more acoustically comfortable solution.
Design and operational benefits
Another key advantage of the F3P forward-curved fans is their compact design, which allows for a more condensed arrangement of components within the unit. Although it requires a spiral housing to generate static pressure, it effectively enables the development of smaller, more space-efficient heat recovery units.
Constant flow
It’s also important to note that constant flow versions of the F3P models include built-in software that automatically adjusts the fan speed in response to changing system resistance. This allows the heat recovery unit to maintain a steady airflow without needing additional flow sensors or external controllers. It significantly simplifies the design, installation, and ongoing operation of the ventilation system.
Summary
F3P fans are perfect for small heat recovery units.
They provide:
– quiet operation,
– high static pressure at low flow rates,
– compact design,
– constant flow operation.
While B3P fans are ideal for larger, more efficient installations, F3P fans are the best option for residential and small commercial use, both regarding technical features and user comfort.
Author: Grzegorz Perestaj, Regional Sales Director, AFL MOTORS