What unit is used to measure the normal supply air volume for furnaces?

The unit used to measure the normal supply air volume for furnaces is cubic feet per minute (cfm). This unit indicates the amount of air that can be supplied or moved by a furnace in one minute, which is crucial for understanding the efficiency and performance of heating systems.

Typically, the airflow requirements for residential heating applications are expressed in cfm, making it a standard metric in the HVAC industry. Adequate airflow is essential for effective heat distribution, ensuring comfort, and maintaining proper system operation.

The other units mentioned have different applications:

• Acfm (actual cubic feet per minute) takes into account actual operating conditions and is often used in industrial contexts where air density might vary.

• L/s (liters per second) is a metric unit often used in Europe and other regions, but it's less common in the North American context for measuring air volume in furnaces.

• Btuh (British thermal units per hour) measures thermal energy, not airflow, and is commonly used to express heating capacity rather than the volume of air supplied.

In HVAC applications, cfm remains the standard unit of measurement for normal supply air volume in furnaces, emphasizing its essential role in heating system specifications and performance evaluations.