During a routine line inspection, the TXV bulb is found on the floor. Where should the bulb be attached for proper meter operation?

• A. The inlet end of the coil
• B. The outlet end of the coil
• C. The compressor discharge line
• D. The receiver inlet

Answer: (B)

The sensing bulb on a TXV must read the temperature of the evaporator outlet so the valve can meter refrigerant based on the evaporator’s actual cooling load. Attaching the bulb to the suction line at the evaporator outlet lets it sense the evaporator outlet temperature, which is what drives the TXV to maintain the proper superheat. If the bulb were placed at the inlet end of the coil, on the compressor discharge line, or at the receiver inlet, it would be reading temperatures that don’t reflect the evaporator’s conditions, causing improper metering, inefficient cooling, and potential compressor issues. Therefore, the bulb should be attached to the suction line at the evaporator outlet.