Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Turn Hot Water Tap On
Gain access to PCB (use Insulation Mat as required)
Attach pressure gauge to gas valve pressure outlet test point
The graduated opening of the gas valve for ignition rate is governed by
the P4 potentiometer control, which is factory set to the mid position.
Confirm / adjust P4 potentiometer to the Mid-Position.
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Reset appliance if required (rotate selector switch to OFF position for 4 seconds, then rotate back to DHW/CH position).
With P4 at Mid-Position, allow appliance to commence its ignition sequence.
Measure the burner pressure ignition rate.
Burner pressure ignition rate should be seen to rise to approximately 3.0 mbar.
Note:
1. Burner pressure should be present approximately 4 to 5 seconds after fan has started to run and remain present for approximately 10 seconds.
2. Appliance may enter lockout during test, reset as required until test complete.
3. When pressure gauge is removed the pressure test point should be tightened and checked for gas tightness.