Question 353Motor Plants - Assistant Engineer

The correct answer is A) "21". The device labeled "21" in the illustration MO-0111 removes air and non-condensable gases from the unit. This is typically an air vent or air release valve, which serves to eliminate air pockets and prevent air from building up in the system. This is an essential function to maintain the proper operation and efficiency of the equipment. The other answer choices are incorrect because they do not represent the component responsible for removing air and non-condensable gases from the unit. Devices labeled "22", "25", and "27" likely serve other functions, such as regulating pressure, controlling flow, or providing access for maintenance, but they do not specifically remove air and non-condensable gases.