What pressures operate a thermostatic expansion valve?

The correct choice highlights the three key pressures that influence the functioning of a thermostatic expansion valve: evaporator pressure, spring pressure, and bulb pressure.

The evaporator pressure is critical because it represents the pressure present in the evaporator, which is pivotal for determining the amount of refrigerant that can flow into the evaporator coil. The thermostatic expansion valve modulates the refrigerant flow to maintain the desired temperature and pressure conditions necessary for efficient cooling.

Spring pressure plays a fundamental role in the valve operation, as it provides a balancing force against the bulb pressure. The spring can be adjusted to set the desired superheat level, which helps in controlling how much refrigerant is release based on the load requirements.

Bulb pressure arises from the sensing bulb that is typically located on the outlet of the evaporator. This bulb contains a refrigerant that responds to temperature changes by creating pressure. When the temperature rises, so does the pressure, causing the expansion valve to open further, allowing more refrigerant to pass through and ensuring optimal system performance.

Together, these pressures ensure the thermostatic expansion valve operates efficiently to maintain the cooling cycle's balance, affecting not only comfort but also the energy efficiency of the system. Other pressures mentioned in the remaining options do