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What electro-mechanical control would you use on a cap tube or automatic expansion valve system to maintain the space temperature?

  1. A dual pressure control

  2. A low pressure control

  3. A thermostatic control

  4. A high pressure control

The correct answer is: A thermostatic control

In the context of maintaining space temperature in a system utilizing a capillary tube or automatic expansion valve, a thermostatic control is the most suitable option. This type of control responds directly to the temperature of the space, making it ideal for regulating the cooling effect and ensuring that the desired temperature is achieved and maintained. Thermostatic control works by using a sensing element, typically a bulb filled with a refrigerant, that expands or contracts based on the temperature changes in the environment. When the space temperature rises above the setpoint, the control signals the system to adjust the flow of refrigerant, thereby modulating the cooling process. This capability allows for precise control over the temperature and enhances the energy efficiency of the system. In contrast, other control options—like dual pressure, low pressure, or high-pressure controls—are typically designed for safety or operational parameters rather than direct temperature control. They focus on ensuring that the system operates within specific pressure ranges, preventing issues such as overpressure or low pressure conditions, rather than managing the temperature of the conditioned space directly.