How should fan speed be set in an HVAC system?

Setting the fan speed in an HVAC system is critically important for ensuring efficient operation and comfort within the conditioned space. The correct choice emphasizes the importance of referring to the temperature rise specified on the data plate. This temperature rise is the difference in temperature of the air entering and exiting the heat exchanger or furnace when the system is running at optimum conditions.

By setting the fan speed according to the temperature rise called for on the data plate, the system can effectively deliver the proper amount of heated air to achieve the desired indoor temperature. This ensures that the system operates within its design parameters, leading to improved efficiency, comfort, and longevity of the HVAC equipment.

Additionally, relying on the temperature rise provides a more precise method of adjustment based on the specific intended performance of the heating system, rather than more subjective methods such as noise level or ambient temperature, which can lead to improper system performance or inefficiencies.