Set Appliance State:

Mains Power Off
Boiler Switch in ON position
Central Heating switch in OFF (central) position
DHW thermostat to MAX
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Turn on hot water tap.
When hot water temperature reaches 38 - 40°C
flow rate will increase to approximately 11.9 litres per min.
Overall there should be 35°C rise in temp at a flow rate of 11.9 litres / min.
From very cold conditions this may take up to 40 seconds.
Temperature rise = 35°C at 11.9 litres per minute.