Set Appliance State:
Set Multimeter to DC Volts 
Turn Hot Water Tap On
Isolate Mains Power to appliance as per TOPs P4
Gain access to PCB (use insulation mat as necessary)
Gain access to PCB (use insulation mat as necessary)
| WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure |
Measurement:
Measure the voltage between the white wire (pin 8) on X20 on the sequence board and neutral on X4 on the main driver board.
Voltage should be approximately 31V DC.
Voltage should be approximately 31V DC.
Isolate as per TOPs P4
and refit as necessary