Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Turn Hot Water Tap On
ON/OFF switch in ON position
DHW temp selector to MAX
Attach temperature clamps to primary flow and return pipes as indicated
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Allow fan to run and the boiler to ignite.
Run the hot water for at least 2 minutes while observing the temperature differential between the flow and return.
The differential should remain below 20°C throughout the test.
Note:
If another fault with the hot water is present (e.g. CH heats on DHW operation) click HERE to investigate.