Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to DC Volts 
DHW Demand
| WARNING! - Mains voltage is expected during test follow TOPs P4 live testing procedure |
Measurement:
Measure voltage between the green wire pin 10 at connector X22 and a suitable earth connection, with the connector X22 attached to the PCB.
Expect 5 vdc.
Expect 5 vdc.
Isolate as per TOPs P4
and refit as necessary