Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to AC Volts 
Selector Switch to Hot Water and Heating
Gain access to PCB (use insulation mat as necessary)
Ensure NO CH demand
Gain access to PCB (use insulation mat as necessary)
Ensure NO CH demand
| WARNING! - Mains voltage is expected during test follow TOPs P4 live testing procedure |
Measurement:
Test for mains voltage between the black wire (top) on connector X9 and earth.
Isolate as per TOPs P4
and refit as necessary