What type of signal operates the solenoid valve in a refrigeration system?

The correct answer is electrical because solenoid valves are designed to be actuated by an electromagnet. In a refrigeration system, when an electric current flows through the solenoid coil, it generates a magnetic field that moves a plunger within the valve. This movement either opens or closes the valve, controlling the flow of refrigerant through the system.

Solenoid valves are favored in refrigeration systems due to their quick response time and reliability, allowing for precise control of the refrigerant's flow. This control is crucial for maintaining system efficiency and performance.

Mechanical, pneumatic, and hydraulic signals are not applicable in the context of solenoid valves because they rely on different principles for actuation. Mechanical signals involve physical movement or mechanical parts, pneumatic relies on compressed air, and hydraulic uses liquids under pressure—all of which do not align with the way solenoid valves function in electrically controlled applications.