In general, the thermal bulb for a thermal expansion valve used in a reciprocating air conditioning system is usually charged with what substance?

Correct Answer: Option A — the same refrigerant as the system

Thermal expansion valves (TXVs) rely on a thermal bulb to sense suction line temperature. To ensure accurate operation and prevent erratic valve response, the bulb is charged with the same refrigerant as the system. This ensures that the pressure-temperature relationship within the bulb matches the system's operating characteristics perfectly.