Question 122Refrigeration & AC - Assistant Engineer

The correct answer is C) the insulation prevents air stream temperatures from influencing the bulb temperature. The reason for this is that the thermostatic expansion valve's sensing bulb needs to accurately measure the temperature of the refrigerant as it exits the evaporator coil. If the bulb is exposed to the temperature of the air stream passing over the evaporator, it can provide an inaccurate reading and cause the valve to malfunction. The insulation around the bulb helps isolate it from the air stream temperature so that it can properly sense the refrigerant temperature and allow the valve to operate as intended. The other answer choices are incorrect because they do not directly address the primary purpose of the insulation, which is to protect the sensing bulb from external temperature influences.