In the heart of a high-capacity heating plant, the Weishaupt G7/1-D
To achieve optimal combustion, the burner must be tuned to a specific CO2 or O2 level in the flue gas.
The manual contains highly detailed isometric drawings. These are invaluable when you disassemble the burner head to clean carbon deposits or replace the ignition electrodes. You will see exactly how the flame tube, diffuser, and swirl plates interact.
Without the manual, you might replace the gas valve (expensive and wrong). With the manual, you clean a tube and turn a dial. That is the power of service documentation.