Set Appliance State:

Turn Hot Water Tap On
Isolate Mains Power to appliance as per TOPs P4
Connect a U-Gauge to the Gas Valve outlet pressure point
On/Off Switch in ON position
Mode Selector Switch to Summer
DHW Thermostat to MAX
WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure
Mains Power On

Measurement:

Does the U-Gauge indicate high gas rate pressure (approximately 10 mbars) and the burner light to a high flame?
Note:
The boiler must not be at its full operating temperature.
Note:
When pressure gauge is removed the pressure test point should be tightened and checked for gas tightness.