Set Appliance State:

Mains Power Off
Isolate Mains Power to appliance as per TOPs P4
Boiler Thermal Store must NOT be at maximum temperature.
Models with Programmer: Rocker Switch to Continuous.
Models without Programmer: Rocker Switch to ON.
Mains Power ON

Observation:

Allow the Boiler to run until the Thermal Store reaches maximum temperature.
Boiler should shut down and the Green Neon will extinguish.