What units are typically used to measure vacuum?

In the context of HVAC refrigeration, vacuum is commonly measured in inches of mercury (inHg). This measurement indicates the pressure exerted by a column of mercury in a barometric tube. In practical applications, when a refrigeration system is evacuated to remove air and moisture, technicians often monitor the vacuum levels using gauges calibrated in inches of mercury.

This unit is particularly useful because it provides a clear reference point for determining how much vacuum has been achieved, which is critical for preventing contamination and ensuring efficient operation of the cooling system. For example, a reading of 30 inches of mercury indicates a near-perfect vacuum, which is essential for effective refrigeration processes.

Other options such as PSI (pounds per square inch), Pascals, and Bar are more commonly associated with pressures above atmospheric levels or are used in different contexts of pressure measurement rather than vacuum. Therefore, when measuring vacuum in refrigeration systems, inches of mercury is the standard unit of choice.