Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Selector Switch to Hot Water and Heating
All heating controls calling
Remove diverter valve motor/actuator
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Wait at least 5 seconds after power On.
Is the actuator in the CH position, spindle fully extended?