Set Appliance State:

Mains Power Off
Boiler mains switch On
Ensure secondary heat exchanger is cool and there is a demand for Preheat
Gas On
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Reset lockout as necessary
Allow fan to run and ignition sequence to commence.
Can sparking be heard and does the burner ignite?