Which instrument would a technician use to calculate return airflow to a furnace?

To calculate the return airflow to a furnace, a technician would use a velometer. A velometer measures the velocity of air moving through a duct system. By knowing the cross-sectional area of the duct and the velocity of the air, the technician can calculate the volumetric airflow rate, which is essential for determining how much air is being returned to the furnace.

This measurement is crucial for ensuring that the furnace operates efficiently and effectively, as proper airflow is necessary for optimal combustion and heat exchange. Understanding air velocity and volumetric flow allows technicians to make informed decisions about system performance and troubleshoot airflow issues.

Other instruments, such as manometers, thermometers, and anemometers, have different primary functions. Manometers measure pressure differences, which may indirectly relate to airflow but do not provide direct velocity measurements. Thermometers measure temperature and are important for assessing thermal conditions but do not measure airflow. Anemometers, while also measuring air velocity, are typically designed for higher precision in specific applications and may not be as relevant when utilizing a velometer specifically designed for duct airflow assessments.