Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to AC Volts 
CH Demand
Integral programmer On
Gain access to appliance terminal strip
Gain access to appliance terminal strip
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 blue connection (SW live) at the controls terminal block, and the blue (neutral) connection on the mains input terminal block.
Expected voltage mains voltage (approx 240 VAC).
Expected voltage mains voltage (approx 240 VAC).
Isolate as per TOPs P4
and refit as necessary