Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to AC Volts 
Gain access to PCB (use Insulation Mat as required)
Selector switch to DHW position
CH temperature selector to minimum
DHW Preheat selector to OFF position
Selector switch to DHW position
CH temperature selector to minimum
DHW Preheat selector to OFF position
| WARNING! - Mains voltage is expected during test follow TOPs P4 live testing procedure |
Measurement:
Test 1.
Measure the voltage across connector A8 connection 3 (white wire) and a suitable earth.
Selector switch to CH position.
Apply CH Demand
Test 2.
Measure the voltage across connector A8 connection 5 (red wire) and a suitable earth.
Measure the voltage across connector A8 connection 3 (white wire) and a suitable earth.
Selector switch to CH position.
Apply CH Demand
Test 2.
Measure the voltage across connector A8 connection 5 (red wire) and a suitable earth.
Isolate as per TOPs P4
and refit as necessary