Question 184Refrigeration & AC - 1st Asst/Chief

The correct answer is A) the insulation prevents air stream temperatures from influencing the bulb temperature. The sensing bulb of a thermostatic expansion valve needs to accurately measure the temperature of the refrigerant leaving the evaporator. Without insulation, the temperature of the air flowing around the sensing bulb could influence the temperature reading, causing the valve to open or close at the wrong times. The insulation helps isolate the sensing bulb from the air stream temperature, ensuring it only responds to the actual refrigerant temperature, which is critical for proper refrigeration system control. The other answer choices are incorrect because they do not directly relate to the primary function of the sensing bulb insulation, which is to prevent external air temperatures from affecting the temperature measurement.