Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
CH Demand
DHW Demand
Attach temperature clamps to flow and return pipes underneath boiler as close to isolation valves as possible
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Skip self-check as necessary.
Set boiler into service mode (hold + and - buttons until display changes - approx. 3 seconds).
Allow boiler to run for approximately 2 minutes or until return pipe begins to heat.
Measure the temperature differential between the flow and return pipes.
The differential should be approximately 25°C or less.
Note:
Temperature differential may be higher on initial start-up.