Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to AC Volts 
Function selector in 0 position
All CH controls calling
Gain access to PCB (use insulation mat as necessary)
All CH controls calling
Gain access to PCB (use insulation mat as necessary)
| WARNING! - Mains voltage is expected during test follow TOPs P4 live testing procedure |
Measurement:
Switch selector to the CH/DHW position, measure the voltage across the black lead (neutral) and red lead (live) in the middle of connector X3 on the PCB.
Expect Mains voltage (230 VAC).
Switch the selector back to HW position.
Run DHW tap
Measure voltage across the black lead (neutral) and white lead (live) in the middle of connector X3 on the PCB.
Expect Mains voltage (230 VAC).
Expect Mains voltage (230 VAC).
Switch the selector back to HW position.
Run DHW tap
Measure voltage across the black lead (neutral) and white lead (live) in the middle of connector X3 on the PCB.
Expect Mains voltage (230 VAC).
Isolate as per TOPs P4
and refit as necessary