Set Appliance State:
Set Multimeter to AC Voltage 
CH Demand
Isolate Mains Power to appliance as per TOPs P4
CH/HW Switch in CH position
Ensure boiler is not in Pre-Heat mode
Gain access to PCB (use insulation mat as required)
Ensure the base of PCB 27 is insulated and not in contact with the boiler
CH/HW Switch in CH position
Ensure boiler is not in Pre-Heat mode
Gain access to PCB (use insulation mat as required)
Ensure the base of PCB 27 is insulated and not in contact with the boiler
| WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure |
Measurement:
Measure mains voltage across the plug-on connector marked DIV L (brown) and DIV N (blue) on PCB 27.
Isolate as per TOPs P4
and refit as necessary