Minnesota Special Engineer Boiler License Practice Exam

Why does the safety relief valve open every time the burner operates on a hot water boiler?

1. The relief valve is malfunctioning

2. The expansion tank is water logged

3. The boiler is overfilled with water

4. The pressure gauge is faulty

The correct answer is: The expansion tank is water logged

The safety relief valve opening every time the burner operates on a hot water boiler is primarily a sign that the expansion tank is water logged. In a hydronic heating system, the expansion tank serves to accommodate the thermal expansion of water as it heats up. When water is heated, it expands and needs a space to occupy; the expansion tank provides that space. If the expansion tank becomes water logged, it loses its ability to cushion the expansion of the heated water. Consequently, as the water temperature rises and pressure increases beyond the safety threshold, the safety relief valve opens to release the excess pressure and prevent possible damage to the boiler or piping. This function is crucial as it helps maintain safe operating conditions within the system. The other options relate to issues that can cause malfunctions but wouldn't systematically lead to the relief valve operating with every burner cycle like a water logged expansion tank would. For example, a malfunctioning relief valve may incorrectly open due to defects, but that would not regularly occur each time the burner operates. Similarly, an overfilled boiler could cause pressure problems, but this is not a guaranteed frequency of occurrence. A faulty pressure gauge may inaccurately display readings but wouldn't necessarily prompt the valve to open repeatedly with each burner cycle. Therefore, recognizing the state