Set Appliance State:

Mains Power Off
Selector Switch to Hot Water and Heating
Ensure there are NO demands
Appliance DHW thermostat to MIN
(this will deactivate the intelligent preheat
function click here for more information)
Appliance CH thermostat to MAX
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Reset appliance if it is in lockout.
(make a note of code if you want to use fault code diagnostics)
The appliance should enter standby and the fan should not be running.
Neither of the demand LED's should be illuminated.