Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
CH Demand
CH Temperature Control set to MAX
Attach pressure gauge to gas valve pressure outlet test point
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Allow burner to ignite and establish.
Monitor the burner pressure. Once the CH flow temperature reaches
approx. 60°C does the burner pressure start to modulate down?
Note:
When pressure gauge is removed the pressure test point
should be tightened and checked for gas tightness.