Set Appliance State:
Mains Power Off
Mode selector switch to Off/Reset position
Set Multimeter to DC Volts 
Turn Hot Water Tap On
Hot water temperature control set to maximum
| WARNING! - Mains voltage is expected during test follow TOPs P4 live testing procedure |
Measurement:
Mode selector switch to DHW position.
Allow burner to ignite and run for at least 1 minute while
measuring the voltage across the modulating solenoid terminals.
Voltage should be greater than 10 volts DC throughout operation.
Allow burner to ignite and run for at least 1 minute while
measuring the voltage across the modulating solenoid terminals.
Voltage should be greater than 10 volts DC throughout operation.
Isolate as per TOPs P4
and refit as necessary