Remedy
No ionisation detected after ignition.
Check the main shut-off valve, open if necessary.
Check the appliance isolation valve, open if necessary.
Measure the gas supply pressure at the rated heat input. If necessary, shut down the appliance and check the gas line.
Check flame sense electrode and connecting lead, replace if required.
Check venturi/injector for potential blockage.
Measure the ionisation current.
Check the protective earth conductor connection (PE) in the control unit.
Check the ignition cable for damage, replace if necessary.
Check functionality of gas valve and replace if necessary.
Check CO2 and O2 settings at min and max output.
Check flue system.
Check combustion air supply.
Check the heat exchanger on the flue gas side for deposits, clean if necessary.