Where should the bulb of the thermal expansion valve be attached during inspection?

When inspecting a thermal expansion valve, the bulb should be attached at the outlet end of the coil. This placement is crucial because the thermal expansion valve regulates refrigerant flow based on the temperature of the refrigerant vapor leaving the evaporator coil. By sensing the temperature at the outlet, the bulb can accurately control the valve position to ensure that the system maintains the desired superheat. This helps prevent liquid refrigerant from returning to the compressor, which can cause damage or inefficiency in the cooling system.

Attaching the bulb at the inlet end of the coil or at the compressor side would not provide an accurate reading of the refrigerant temperature immediately after it has evaporated, leading to improper control of refrigerant flow. Similarly, placing the bulb close to the refrigerant tank would not reflect the conditions in the evaporator coil, where the thermal expansion valve needs to respond to changes in refrigerant temperature.