Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to AC Volts 
| WARNING! - Mains voltage is expected during test follow TOPs P4 live testing procedure |
Boiler On/Off switch ON
External controls calling
External controls calling
Measurement:
Measure voltage across connection L2 and the connection marked N in main terminal block.
Note:
If no external controls are fitted a link must be fitted between connections L1 and L2.
Note:
If no external controls are fitted a link must be fitted between connections L1 and L2.
Isolate as per TOPs P4
and refit as necessary