Set Appliance State:

Gas Off
Isolate Mains Power to appliance as per TOPs P4
CH Demand
Attach U-gauge to burner pressure test point
Heating temperature selector to MAX
Programmer or selector switch set to heating and hot water
Hot water temperature selector to OFF
Gas On; Pilot On
WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure
Mains Power On

Measurement:

Observe the U-gauge.
Is the boiler correctly range rated for the size and design of the heating system?
Notes:
1. Refer to appliance data badge for specific values and manufacturer's instructions for how to adjust if necessary.
2. When pressure gauge is removed the pressure test point should be tightened and checked for gas tightness.