What causes the burners to dim off after lighting, within 2-3 seconds?

The situation where the burners dim off shortly after lighting, typically within 2-3 seconds, is commonly due to bad flame rectification. In HVAC systems that utilize gas burners, flame rectification is a critical safety feature that ensures the flame is indeed present.

When the burners ignite, a flame sensor or rectification device is supposed to detect the flame. If the sensor is dirty, malfunctioning, or improperly located, it may fail to identify the flame, causing the safety system to shut off the gas flow. This action protects against potential gas leaks and maintains system safety.

If the flame rectification is not functioning correctly, it does not send a signal to the control system that the burner is operating safely, leading to the burners shutting off shortly after they light. This makes understanding flame rectification crucial for troubleshooting issues related to burner operation.

The other options refer to different underlying issues. Insufficient gas pressure can cause issues, such as a weak flame, but would not typically result in a burner lighting and then turning off quickly. A faulty igniter may prevent the burner from igniting in the first place. A blocked flue could lead to safety shutdowns as well, but the immediate reaction of the burners dimming after ignition is more