The external equalizer line used with a thermostatic expansion valve is to compensate for which phenomenon?

The external equalizer line used with a thermostatic expansion valve is to compensate for which phenomenon?

• A. Air friction over the evaporator
• B. Refrigerant pressure drop across the valve orifice
• C. Refrigerant friction through the evaporator
• D. Superheat

Answer: (C)

The external equalizer line is used to account for pressure losses inside the evaporator caused by refrigerant flowing through it. As the refrigerant moves along the evaporator coils, friction creates a pressure drop from the inlet to the outlet. If the valve sensed pressure upstream, it would meter refrigerant based on a higher pressure than actually present at the evaporator outlet, leading to improper flow and unstable superheat. By delivering the evaporator outlet pressure through the external equalizer, the TXV responds to the true evaporating pressure where the refrigerant exits the coil, allowing it to meter more accurately and maintain the desired superheat.

The external equalizer line is used to account for pressure losses inside the evaporator caused by refrigerant flowing through it. As the refrigerant moves along the evaporator coils, friction creates a pressure drop from the inlet to the outlet. If the valve sensed pressure upstream, it would meter refrigerant based on a higher pressure than actually present at the evaporator outlet, leading to improper flow and unstable superheat. By delivering the evaporator outlet pressure through the external equalizer, the TXV responds to the true evaporating pressure where the refrigerant exits the coil, allowing it to meter more accurately and maintain the desired superheat.