Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to DC Volts Set meter to measure DC Volts
Gain access to PCB (use Insulation Mat as required)
Ensure NO demands
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Test 1:
Measure the DC voltage between pin 3 (green) on
connector X5 and a suitable earth point.
Expect 3.7V DC with no demand.
Test 2:
Turn the hot water tap ON, ensure a flow rate above 3 l/min.
Repeat Test 1 again.
Expect 3.2V DC with a hot water demand.