What happens to a low pressure control wired in series with a thermostat and motor if the TXV is stuck in the closed position?

When a thermal expansion valve (TXV) is stuck in a closed position, it prevents refrigerant flow through the system. This results in a drop in pressure within the evaporator coil and affects the functionality of the entire HVAC system.

In this scenario, a low pressure control (which is designed to monitor and maintain the pressure in the system) wired in series with a thermostat and motor will respond to the loss of pressure. As the pressure decreases and falls below the setpoint of the low pressure control, the control will cut out to protect the system from potential damage, such as a loss of lubrication or overheating. Since the low pressure control effectively interrupts the power supply to the motor when the conditions are not met, the motor remains inoperative, thereby preventing unwanted operation and further stress on the system.

This safeguard ensures that the system does not try to run under conditions that could lead to further complications or failures, highlighting the important role of controls in refrigeration and air conditioning mechanics.