In HVAC systems, how is manifold gas pressure expressed?

Manifold gas pressure in HVAC systems is expressed in inches of water column, which is a unit of measurement used to gauge low pressures, particularly in gas applications. This unit is suitable for measuring pressures within the operating range of HVAC systems, capturing the subtle pressure differentials that can significantly affect performance and efficiency.

Inches of water column provides a precise measurement for small pressure changes, which is especially critical in applications such as gas furnaces and burners. This detail is vital in ensuring that these systems operate within the specifications set by manufacturers and codes.

Other units like Pascals, inches of mercury, and PSI are typically used for different applications or ranges of pressures. Pascals can be used for general pressure measurements but are less common in HVAC contexts. Inches of mercury is often reserved for measuring atmospheric pressure or vacuum systems, while PSI (pounds per square inch) is more suited to measuring higher pressures, such as those found in refrigerant systems rather than gas pressure in HVAC systems.