Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
CH Demand
CH temperature control to maximum
DHW temperature control to minimum
Loosen the outlet test point screw (P2) and attach U-gauge to the test point.
WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure
Mains Power On

Measurement:

Allow boiler to fire and run.
After approximately 90 seconds, burner pressure should increase to its set pressure.
Slowly turn the CH temperature selector anti-clockwise.
As the temperature demand is satisfied, does the burner pressure reduce to its minimum setting?
Notes:
1. If CH burner pressure has been set at its minimum rate, then modulation will not take place.
2. When pressure gauge is removed the pressure test point should be tightened and checked for gas tightness.