Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to AC Volts 
DHW Demand
CH Demand
Locate the Orange wires in the wiring centre
| WARNING! - Mains voltage is expected during test follow TOPs P4 live testing procedure |
Measurement:
Measure voltage to earth on the Orange wire(s).
The Orange wire takes the voltage from the valves end switch to supply the power to run the pump and boiler.
Is mains voltage present on the Orange wire(s)?
Note: The colour and position of the wires will vary between systems and components.
The Orange wire takes the voltage from the valves end switch to supply the power to run the pump and boiler.
Is mains voltage present on the Orange wire(s)?
Note: The colour and position of the wires will vary between systems and components.
Isolate as per TOPs P4
and refit as necessary