Question 251General Subjects - Assistant Engineer

The correct answer is B. If there is an increase in demand for fuel by the boiler, the fuel oil heater fuel outlet temperature would decrease, causing the remote bulb pressure to decrease. This would make the control diaphragm flex upward, and through lever action, further open the pilot valve. This allows more heated fuel oil to flow to the boiler, increasing the fuel oil heater fuel outlet temperature back to the desired setpoint. The other options are incorrect because they do not accurately describe how the temperature control valve would initially respond to an increase in fuel demand by the boiler. Options A and D describe the opposite response, where the valve would close instead of open. Option C describes the valve closing instead of opening in response to a decrease in fuel oil heater fuel outlet temperature.