Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to AC Volts Set meter to measure AC Volts
Gain access to PCB (use Insulation Mat as required)
Programmer or selector switch set to hot water only
Hot water temperature selector to maximum
Heating temperature selector to OFF
Ensure heatbank is not up to temperature (this can be achieved by running the DHW with the mains power to the appliance on and the gas to the appliance turned off)
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Measure voltage across connection L (brown wire) and connection N (blue wire) at connector CN1 on the ignition PCB.