REFRIGERANT FLOW CONTROLS IN HVACR SYSTEMS Understanding Metering Devices, Applications, Advantages, and System Protection Every vapor-compression HVACR system requires a method of controlling refrigerant flow between the high-pressure and low-pressure sides of the system. This component is commonly called a: Refrigerant control Metering device Expansion device Refrigerant flow-control device The metering device performs two essential functions: It creates the pressure drop that allows high-pressure liquid refrigerant to enter the lower-pressure evaporator. It regulates the quantity of refrigerant entering the evaporator so that the coil can absorb heat without starving, flooding, or returning excessive liquid refrigerant to the compressor. Historically, six major types of refrigerant controls have been associated with HVACR system design: Thermostatic Expansion Valve Capillary Tube Automatic Expansion Valve High-Pressure-Side Float Valve Low-Pressure-Side Float Valve Electronic ...