Home Inspection State Practice Exam

What component is involved in controlling when a hot water boiler activates?

1. A thermostat

2. An aquastat

3. A circulator pump

4. A pressure relief valve

The correct answer is: An aquastat

The component that controls when a hot water boiler activates is the aquastat. This device monitors the temperature of the water in the boiler and signals the burner to start or stop based on the water's temperature relative to a setpoint. When the water temperature falls below the desired level, the aquastat activates the boiler to heat the water. Once the appropriate temperature is reached, it will shut the boiler off to maintain energy efficiency and prevent overheating. While a thermostat is commonly associated with controlling temperature in heating systems, it generally pertains to regulating air temperature in living spaces rather than the water temperature in a boiler system. The circulator pump, on the other hand, is responsible for moving the heated water through the system but does not control boiler activation. Lastly, the pressure relief valve ensures safety by alleviating excessive pressure within the boiler but is not involved in turning the boiler on or off. Thus, the aquastat is the correct component tied directly to the control of the boiler's operational cycles.