Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to AC Volts 
Ensure there is no demand for either CH or DHW
Gain access to PCB (use insulation mat as necessary)
Gain access to PCB (use insulation mat as necessary)
| WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure |
Measurement:
Measure the voltage across the Blue and Brown leads on connector JP4 on the PCB.
Expect Mains Voltage.
Expect Mains Voltage.
Isolate as per TOPs P4
and refit as necessary