Which three instruments are essential for checking the calibration of an enthalpy control on an economizer of a rooftop air conditioning unit?

The essential instruments for checking the calibration of an enthalpy control on an economizer of a rooftop air conditioning unit include a sling psychrometer, thermometer, and multimeter.

The sling psychrometer is crucial for measuring the wet-bulb and dry-bulb temperatures, which are needed to determine humidity and enthalpy levels. Understanding the humidity conditions is vital for the effective operation of an economizer, as it helps in assessing when it is appropriate to use outside air for cooling to optimize energy use while maintaining comfort.

The thermometer is also fundamental, as it provides accurate temperature readings essential for assessing the performance of the HVAC system and ensuring it operates within the designed temperature parameters.

Additionally, the multimeter is used for electrical measurements, which are important when verifying the functionality and calibration of the electrical components of the economizer control system. This includes checking for proper voltage and current in the control circuits to ensure they are functioning correctly.

Together, these instruments enable a comprehensive evaluation of the economizer's operation, helping to ensure it is calibrated properly for efficient air conditioning system performance.