Question 71Motor Plants - QMED

The correct answer is D) changing the spring compression opposing the bellows. In an adjustable bellows type thermostatic valve, the temperature at which the valve operates is determined by the compression of the spring that opposes the bellows. Increasing the spring compression raises the temperature at which the valve opens, while decreasing the spring compression lowers the operating temperature. This allows the user to adjust the valve to the desired temperature setpoint. The other options are incorrect because they do not directly affect the operating temperature of the valve. Changing the position of the actuating bulb (A) or varying the air loading pressure (B) do not impact the spring compression, while replacing the bellows with a heavier spring (C) would change the valve's characteristics rather than allowing adjustment.