Which control is used to monitor refrigerant liquid level?

• A. Float switch
• B. Thermostat
• C. Capillary tube
• D. Pressure relief valve

Answer: (A)

Monitoring refrigerant liquid level relies on a float switch. A buoyant float rises and falls with the liquid, and its movement opens or closes an electrical circuit to control a pump, valve, or other device to maintain the desired liquid height in a receiver, sump, or similar reservoir. Keeping the level correct prevents liquid from reaching the compressor (which can cause damage) and ensures there’s enough liquid for the metering device downstream.

The other components play different roles: a thermostat senses temperature to control heating or cooling, not liquid height; a capillary tube is a metering device that constrains refrigerant flow based on pressure and temperature, not level; a pressure relief valve protects against overpressure rather than monitoring liquid height.