Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to AC Volts 
Gain access to PCB (use Insulation Mat as required)
| WARNING! - Mains voltage is expected during test follow TOPs P4 live testing procedure |
Measurement:
Measure (high) voltage between connector PL6 connection 5 (orange) and good earth point on boiler case.
Isolate as per TOPs P4
and refit as necessary