Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
CH Demand
Unscrew control box and fit it to the bottom lugs so access to the pipes can be gained
Use FGA temperature clamps on Flow and Return pipes as close to the combustion chamber as possible
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Allow the boiler to run and start to heat up to system, measure the differential temperature between the flow and return. The expected temperature difference should be between 11-20 degrees.