Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to AC Volts 
CH Demand
Gain access to PCB (use insulation mat as necessary)
| WARNING! - Mains voltage is expected during test follow TOPs P4 live testing procedure |
Measurement:
Ensure external controls are calling for ch demand.
Measure for ac voltage across connections 4 (black) and 5 (black) of connector CN1 on the PCB.
Expected voltage should be approx. 0 volts.
Measure for ac voltage across connections 4 (black) and 5 (black) of connector CN1 on the PCB.
Expected voltage should be approx. 0 volts.
Isolate as per TOPs P4
and refit as necessary