Set Appliance State:

Gas On; Pilot On
CH Demand
Isolate Mains Power to appliance as per TOPs P4
On/Off Switch in ON position
Mode selector switch to Constant
Connect a U-Gauge to the Gas Valve outlet pressure point
WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure
Mains Power On

Measurement:

Measure the burner pressure at the Gas Valve, this should lie between 1.2 mbar (low rate) and 9.5 mbar (high rate).
Note:
When pressure gauge is removed the pressure test point should be tightened and checked for gas tightness.