Set Appliance State:

Mains Power Off
Turn Hot Water Tap On
Selector switch set to CH/DHW
DHW temperature control set to MAX
Preheat switched OFF
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

With a flow rate between 8.0 - 9.0 l/min allow the boiler to run for hot water for approx. 5 minutes.
Does overheat lockout (L1 fault code) occur?
Note.
If a fault code other than L1 appears CLICK HERE.