Which procedure best increases the furnace blower speed?

To increase the furnace blower speed effectively, adjusting the motor pulley is a key procedure. Specifically, closing up the motor pulley, which means decreasing its diameter, results in an increase in the speed of the blower fan. This is due to the principle of pulley systems, where a smaller driving pulley rotates faster than a larger driven pulley, thereby increasing the RPM (revolutions per minute) of the blower motor.

This adjustment is a common method in HVAC systems for optimizing airflow without needing additional systems or components, making it both a practical and efficient approach. It allows for better control of the air distribution in the heating system, which can lead to improved heating performance and comfort in the living space.

While changing the pulley size directly impacts blower speed, the other options focus on different aspects. Changing the return air duct size or installing a higher horsepower fan motor could also affect airflow but do not directly modify the speed of the blower in the same manner as adjusting the pulley does.