Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Remove diverter valve actuator, place in a safe position where the spindle can be observed
Use insulation Mat as required
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Apply a CH demand.
After 40 seconds
Isolate Mains Power to appliance as per TOP's P4

With the aid of a screwdriver confirm the actuator spindle
is in CH position and cannot be pushed down.