What is the purpose of the equalizing line in a thermostatic expansion valve?

• A. Compensates for pressure loss in the evaporator
• B. Regulates refrigerant temperature in the suction line
• C. Prevents frost in the evaporator
• D. Controls flow through the purge valve

Answer: (A)

The equalizing line provides a pressure path from the evaporator to the valve so the TXV can see the evaporator pressure accurately. By equalizing the pressure across the evaporator, it compensates for pressure losses that occur as refrigerant flows through the coil. This lets the valve respond to the true evaporator pressure and maintain the desired superheat, rather than reacting to a higher pressure upstream. The other ideas don’t fit this role: it doesn’t directly regulate suction line temperature, prevent frost on the evaporator, or control flow through a purge valve.