Set Appliance State:

Mains Power Off
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?
Note: If CH burner pressure has been set at its minimum rate, then modulation will not take place.
When the U-gauge is removed, ensure the pressure test point is checked for soundness.