What is the role of a pressure switch in a noncondensing furnace?

The role of a pressure switch in a noncondensing furnace is fundamentally to ensure the safe and proper operation of the induced-draft blower. This component is critical because it acts as a safety device that verifies the functionality of the blower, which is responsible for venting combustion gases out of the furnace.

When the induced-draft blower operates, it creates a negative pressure in the flue or venting system. The pressure switch detects this negative pressure and confirms that the blower is working effectively. If the blower fails to operate or if there is an obstruction in the venting system, the pressure switch will not close, which prevents the furnace from lighting. This mechanism ensures that potentially hazardous combustion gases are not released into the living space, thus playing a crucial role in maintaining safety standards in furnace operation.

The other choices pertain to different functions that are either not associated with the pressure switch or are served by other components in the furnace system. For example, temperature control is typically managed by a thermostat, and gas levels are monitored by gas valves or regulators. Safety controls may also involve flame sensors or other safety mechanisms that are separate from the pressure switch's core function.