Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to AC Voltage 
Boiler On/Off Switch ON
CH Switch ON
DHW Switch in INSTANT position
CH Temperature Control in Maximum position
CH Switch ON
DHW Switch in INSTANT position
CH Temperature Control in Maximum position
| WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure |
Measurement:
Measure the voltage across terminal marked 3 and the neutral terminal (blue wire, marked 1Mp) on the main terminal block.
Isolate as per TOPs P4
and refit as necessary