What symptoms would indicate an open cad cell?

An open cad cell typically indicates a lack of continuity in the photocell that monitors the flame in an oil burner system. When the cad cell does not detect the presence of a flame due to being open, it triggers a safety mechanism that prevents the burner from starting. This is a crucial safety feature; without a flame to monitor, the system will not operate to avoid potential hazards such as unburned oil accumulation or a fire risk.

In summary, the burner not starting reflects the role of the cad cell in the safe operation of the heating system. The cad cell is designed to ensure that ignitions only occur when there is a flame detected, maintaining safety and proper functioning of the oil burner.