Set Appliance State:

Mains Power Off
Gas On; Pilot On
Turn Hot Water Tap On
Selector Switch OFF
Gas Control Knob in Main Burner position
WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure
Mains Power On

Measurement:

Is there a 35 degree C rise in the Hot Water temperature for a flow rate of 12 litres per minute?