What must a TXV have when used with a compressor driven by a PSC motor to reduce the required torque on startup?

When a thermal expansion valve (TXV) is used with a compressor that is driven by a permanent split capacitor (PSC) motor, having an internal bleed port is essential to help manage the startup torque requirements. The internal bleed port allows refrigerant to flow through the valve even when the compressor is not running. This continuous flow helps to ensure that the suction line does not become too low in pressure, which could otherwise demand higher torque from the motor upon startup.

The presence of the bleed port allows the evaporator to maintain a certain level of refrigerant pressure, preventing the compressor from having to work excessively hard to start up against a high differential pressure. This design feature helps improve reliability and efficiency, making it particularly important in applications where starting torque could be a concern.

The other options, while they may have benefits in different contexts, do not specifically address the requirement for reducing startup torque in a scenario involving a PSC motor with a TXV.