Which switch actuates the ignition control during the startup of a high-efficiency noncondensing furnace?

The pressure switch is the component responsible for actuating the ignition control during the startup process of a high-efficiency noncondensing furnace. Its primary function is to monitor the pressure within the system, ensuring that there is adequate venting and that the combustion air supply is sufficient before allowing ignition to occur. This safety feature prevents the furnace from igniting if there is a failure in the venting system or if the proper airflow is not present, reducing the risk of hazardous conditions.

By detecting whether the pressures are within the specified range, the pressure switch ensures that the furnace operates safely and efficiently. If the conditions are not met, the ignition control will not be activated, thereby preventing unsafe operation and potential damage or hazardous situations.

Interlock switches generally serve to prevent equipment from being operated under unsafe conditions, but they do not directly interact with the ignition sequence. The thermostat is primarily responsible for setting the desired temperature and does not control the ignition directly. Flow switches are often used in systems to confirm fluid movement but are not involved in the ignition sequence for a furnace.

This understanding of how the pressure switch functions within the system highlights its critical role in safe and effective furnace operation.