Simplified Constant Air Volume Solution — Seemtek Blower Fan

As a professional provider of fan solutions, Seemtek has introduced Blower Fans with constant air volume (CAV) control technology in residential heat recovery units. This fan solution effectively addresses the problem of decreasing airflow as the filter in the main unit becomes clogged, ensuring constant airflow from the main unit to meet the constant airflow requirements of the heat recovery unit, thereby optimizing indoor air quality.

Traditional industrial CAV control uses external pressure sensors or airspeed sensors and feedback circuits. As static pressure changes with different fan duct installations or duct dust accumulation, fan CAV control can continuously output constant airflow across a wide range of static pressures to maintain comfortable ventilation. Installing airflow detection sensors at the outlet or inside the duct measures airflow to control the fan system's constant airflow output. However, airflow detection sensors are expensive, complicated to install, and have high hardware costs. There is also the risk of measurement failure or inaccuracy due to sensor malfunction. Additionally, existing CAV control solutions without airflow sensors can only achieve one or a few constant airflow curves, each requiring detailed testing and complex calculations, resulting in highly complex designs, relatively low control precision, and high implementation costs. It is also challenging to achieve constant airflow control with multiple outlets, affecting environmental control efficiency.

For residential heat recovery units and low airflow delivery needs, Seemtek's Blower Fan analyzes the changes in the steady-state working point of the motor speed when the system output target airflow changes due to varying air resistance conditions, based on the relationship between static pressure, electrical power, airflow, and speed. This leads to a power feedback-based fan air resistance adaptive constant airflow control technology.

Seemtek's CAV control method for fans enhances the ability to output constant airflow by adjusting the speed under different air pressures, simplifying the testing and calculation methods of airflow characteristics, avoiding complex computations. It calculates the target speed range based on the fan's airflow, air pressure, and preset constant airflow mathematical model; determines the required current compensation value to achieve the target speed range, and compensates the fan's current to control the output airflow at the target constant airflow value. Compared to traditional external pressure sensor and feedback circuit methods, this approach represents a significant innovation. Utilizing the basic characteristics of forward-curved centrifugal fans and adopting EC motor PID closed-loop control technology, the motor intelligently adjusts speed and current to maintain constant airflow within a certain static pressure range.

This technology not only effectively addresses the issue of achieving constant airflow in all outlets in multi-outlet ventilation systems but also improves the operating level and quality of the ventilation fan. It is more reliable, economical, energy-saving, and maintains more consistent airflow.

By implementing Seemtek's CAV fan, the following can be achieved:

1. Ensures constant supply and exhaust airflow, maintaining fresh indoor air.

2. Maintains a positive indoor pressure differential, ensuring all air enters through the filters.

3. Monitors the filter, preventing clogs, facilitating timely maintenance and replacement, and improving fresh air quality.

Seemtek———Tailoring Solutions for Fan Industry