Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
NOT CURRENTLY USED
NOT CURRENTLY USED
NOT CURRENTLY USED
NOT CURRENTLY USED
Gain access to lower PCB panel
If it has been removed, refit the link between Lr for HW and L
External controls (if fitted) calling for preheat
Ensure there is a demand for preheat,
this can be achieved by running the HW tap with the
gas off and the appliance turned on
Gas On
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Reset appliance as necessary.
Allow the boiler to complete its self check.
Does the appliance fire for preheat?
If the appliance does NOT fire for preheat:
Hold the ECO button down for 10 seconds.
Does the appliance now fire for preheat?
Appliance fires for preheat
Appliance does not fire for preheat