Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to AC Voltage 
CH Demand
Control Thermostat in high position
| WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure |
Measurement:
Allow the Boiler to purge itself and the Burner to ignite.
Measure the voltage across the connector (marked C1) connection 7 (purple wire) on the Main PCB and the Neutral wire (Blue) identified as N on the main connector block on the Interconnection Board.
Measure the voltage across the connector (marked C1) connection 7 (purple wire) on the Main PCB and the Neutral wire (Blue) identified as N on the main connector block on the Interconnection Board.
Isolate as per TOPs P4
and refit as necessary