Which of the following is NOT a part of a hand-fired boiler?

In a hand-fired boiler, components are specifically designed to facilitate the operation and maintenance of the boiler system that relies on manual fuel feeding and combustion control. A thermostat is generally used in modern automated or controlled heating systems to regulate temperature; however, in traditional hand-fired boilers, managing temperature is done manually, typically through the adjustment of fuel input and airflow.

The lance is used to inject additional air or fuel into the combustion area, valves are present to control the flow of steam or water, and strainers help to filter out impurities within the water system. Therefore, acknowledging that the thermostat's role is not aligned with the manual operation of a hand-fired boiler allows us to identify it as not a part of this type of boiler system.