ESCO Air Conditioning Practice Exam

A decrease in superheat causes the thermostatic expansion valve to begin to

1. Close

2. Open

3. Remain constant

4. Malfunction

The correct answer is: Close

A decrease in superheat causes the thermostatic expansion valve to begin to close. Superheat is the temperature of the refrigerant vapor above its saturation temperature. When superheat decreases, it indicates that more refrigerant is entering the evaporator coil than needed for the heat load. In response to this, the thermostatic expansion valve starts to close to regulate the flow of refrigerant into the evaporator coil, maintaining the optimal amount for efficient cooling. This adjustment helps in preventing the evaporator from getting flooded with excess refrigerant, which can lead to decreased system efficiency and performance issues.