Question 362Motor Plants - Assistant Engineer

The correct answer is B) 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 expansion of the bellows. Increasing the spring compression raises the temperature setpoint, while decreasing the compression lowers the setpoint. This allows the operator to adjust the valve's temperature response as needed. The other answer choices are incorrect because they do not directly influence the valve's temperature setpoint in the same way as adjusting the spring compression.