If a refrigerant saturation pressure gauge is used in a system with chilled water, the reading primarily indicates the temperature of which component?

• A. The refrigerant in the condenser
• B. The chilled water being pumped to the cooled spaces
• C. Room air temperature
• D. Outdoor air temperature

Answer: (B)

The reading on a refrigerant saturation pressure gauge on a system with chilled water reflects the temperature of the fluid being cooled—the chilled water in the evaporator loop. In the evaporator, the refrigerant is at its saturation temperature corresponding to its pressure, and heat transfer from the water to the refrigerant sets that temperature. Thus, the gauge’s saturation temperature essentially mirrors the water temperature as it is being cooled and circulated to the cooled spaces. It doesn’t indicate room air, outdoor air, or high-side condenser conditions.