What is an example of a variable speed fan in HVAC systems?

In HVAC systems, a variable speed fan is one that can adjust its rotational speed based on the specific requirements of the system at any given time. This allows the fan to optimize airflow and energy efficiency by responding dynamically to cooling or heating demands.

By varying the speed, the fan can provide precise control over the indoor climate, ensuring comfort and reducing energy consumption compared to fans that run at a constant speed. When there is less need for cooling, the fan will slow down, saving energy and enhancing system efficiency. Conversely, when higher performance is required due to increased temperature or cooling load, the fan can ramp up its speed accordingly.

This ability to adjust to conditions directly correlates with effective energy management and system performance, enabling the HVAC system to work more efficiently while maintaining desired indoor temperatures. The other options describe fan behaviors that do not adjust based on the cooling needs, which is why they do not fit the definition of a variable speed fan.