🔍 Key Concepts

• Behavior of a chilled water loop under varying cooling loads • Relationship between supply vs. return temperature in hydronic (water) systems • How compressor suction and discharge conditions respond to load changes

💭 Think About

• In a chilled water air conditioning system, which variable is normally controlled by the plant so that the rest of the system (valves, flow rates) can modulate to match changing load? • Between supply temperature, return temperature, and compressor conditions, which one do designers try to keep steady so the air handling units can accurately control room air temperature? • Think about which parameter would naturally change as the building/space gets warmer or cooler, and which parameter is set as a fixed target by the chiller controls.

✅ Before You Answer

• Identify which temperature (supply or return) is typically used as the control setpoint on a chilled water plant. • Consider whether compressor suction pressure or discharge temperature are stable in real operation when cooling load rises or falls. • Ask: If this one parameter drifts up and down with load, would it still allow consistent air temperature control at the coils? If not, it’s probably not the one that should remain constant.