Set Appliance State:
Set Boiler Control Thermostat to MAX position
Set Multimeter to AC Volts 
DHW Demand
Isolate Mains Power to appliance as per TOPs P4
Ensure external controls are calling for heat
Use insulation mat as required
Ensure external controls are calling for heat
Use insulation mat as required
| WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure |
Measurement:
Measure the voltage across the switched live connection (marked SwL, red wire) and the neutral connection (marked N, blue wire) at the terminal block.
Mains voltage expected.
Mains voltage expected.
Isolate as per TOPs P4
and refit as necessary