Set Appliance State:
Mains Power Off
Set Multimeter to AC Volts 
CH Demand
Integral programmer On
Selector Switch to Hot Water and Heating
| WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure |
Observation:
Measure voltage across the brown connection (live)
at the controls terminal block, and the blue (neutral) connection on the mains input terminal block.
Expected voltage mains voltage (approx 240 VAC).
at the controls terminal block, and the blue (neutral) connection on the mains input terminal block.
Expected voltage mains voltage (approx 240 VAC).
Isolate as per TOPs P4
and refit as necessary