Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to DC Volts Set meter to measure DC Volts
Turn Hot Water Tap On
Adjust DHW flow rate to approx. 6 litres/min
DHW Temperature Control set to MIN
Ensure boiler is cool, this can be achieved by turning the gas off
and running a hot tap with the power on to the appliance
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Allow burner to ignite and establish.
Monitor the DC voltage between the white wires
(30 & 31) at the right hand plug on the PCB.
The voltage should initially reach approximately 20V DC
then as the appliance starts to reach temperature (after
approximately 45 seconds) the voltage should decrease.