What is the normal sequence of operation for a relay module on a forced air furnace?

The normal sequence of operation for a relay module on a forced air furnace follows specific steps to ensure safe and efficient operation. The correct sequence, which is highlighted in the chosen answer, includes pre-purge, trial for ignition, run, and post-purge.

During the pre-purge phase, the system clears out any unburned fuel or gases that may have built up in the combustion chamber before ignition occurs. This step is crucial for safety, as it helps to prevent explosions or backfires. Following pre-purge, the trial for ignition phase begins, where the system initiates the ignition process. This can involve a spark ignition or a hot surface ignition to light the burner.

Once ignition is confirmed, the furnace enters the run phase, in which the burners operate and heat is generated to warm the air that is circulated throughout the space. After the heating cycle is complete, the post-purge phase activates. This involves running the blower to exhaust any remaining combustion gases from the furnace, ensuring that no harmful fumes are released into the living area.

This sequence is designed not only for operational efficiency but also to maximize safety during the heating cycle. The other choices represent various sequences or processes that do not accurately reflect the standard operation of a forced air