Where should the external equalizing line be installed in relation to the thermostatic expansion valve?

The external equalizing line should be installed downstream of the thermostatic expansion valve. This line allows for pressure equalization between the sensing bulb of the expansion valve and the evaporator, ensuring that the valve can operate effectively and maintain the desired superheat level.

By installing the equalizing line downstream, the expansion valve is able to respond accurately to changes in refrigerant pressure within the evaporator. This positioning helps in compensating for pressure drops that may occur as the refrigerant moves through the system, which is crucial for maintaining proper cooling efficiency and system performance.

If the equalizing line were placed upstream or at the inlet, it could lead to fluctuations in valve performance, causing inefficient operation and potential system issues. Placing it at the outlet would not provide the necessary information for proper control of the expansion valve in relation to the evaporator conditions. Therefore, the correct placement ensures optimal functionality of the HVAC system.