The external static pressure (ESP) of a system is measured in __________.

The measurement of external static pressure (ESP) in a heating, ventilation, and air conditioning (HVAC) system is primarily expressed in inches of water gauge (in. w.g.). This unit is specifically suited for measuring low-pressure differentials, which is common in HVAC applications.

Inches of water gauge is practical in this context because it allows for a precise understanding of pressure changes that can affect airflow and system efficiency. It reflects how much pressure the system can exert on the air within the ducts, which is crucial for diagnosing performance issues and ensuring that the system is operating efficiently.

Other units mentioned, such as pascals (Pa), pounds per square inch (psi), and millimeters of mercury (mmHg), are used in various contexts but are less common for measuring the low pressures typically encountered in ductwork and air distribution systems. In HVAC applications, utilizing inches of water gauge allows professionals to communicate about and troubleshoot air pressure concerns effectively, making it the standard unit for this purpose.