What type of pressure do HVACR technicians use that compares pressure to atmospheric pressure?

Gauge pressure is the type of pressure that compares the pressure of a system to atmospheric pressure. When technicians use a gauge to read pressure, they are typically looking at how much pressure is present relative to the surrounding atmosphere, which is why gauge pressure is an effective measurement for practical applications in HVACR systems.

For example, if a system's gauge reads 30 psi, it indicates that the pressure inside the system is 30 psi higher than the atmospheric pressure. This is particularly useful because it gives technicians an understanding of how well the system is performing compared to the pressure exerted by the atmosphere surrounding it, which can influence how refrigerants behave and how efficiently a system runs.

Other types of pressure such as absolute pressure, which measures pressure relative to a perfect vacuum, may be used in specific contexts but do not provide the same practical applicability as gauge pressure when it comes to most HVACR scenarios. Similarly, vacuum pressure refers to measurements made below atmospheric pressure, and barometric pressure pertains specifically to atmospheric conditions without reference to a specific system's operational status.