Set Appliance State:

Mains Power Off
Set Multimeter to mVolts DC Set meter to measure DC mVolts
Turn Hot Water Tap On
Selector Switch in HOT WATER position
WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure
Mains Power On

Measurement:

Depress the Gas Control Knob, allow the Boiler to execute its purge period and the Pilot to ignite. Keep the Gas Control Knob depressed and measure the millivoltage between the thermocouple interrupter at the Gas Valve and a suitable earth point.