If a flame failure occurs during operation, the fuel feed shuts off immediately and the system tries a restart, with preventilation and retried ignition. If no flame results, the control box indicates a fault after the safety period expires. A restart takes place in all cases following a mains power failure. The control box shows a fault if the photoelectric cell detects a light source during the preventilation time, after the safety time.

The control device may only be plugged in or unplugged, if the main switch is in the “OFF” position or if the 7-pin plug connector is disconnected, because the bottom part of the control device carries 230 V.

External light on the photo-cell or flame detector must be prevented (e.g. red-hot fireclay lining). Only then is fault-free operation of the installation ensured.