Set Appliance State:
Mains Reset Switch OFF
Set Multimeter to AC Volts 
Isolate Mains Power to appliance as per TOPs P4
CH Demand
DHW switch to OFF
Remove control panel rear cover to expose main PCB
CH Demand
DHW switch to OFF
Remove control panel rear cover to expose main PCB
| WARNING! - Mains voltage is expected during test follow TOPs P4 live testing procedure |
Measurement:
Mains reset switch On.
CH selector switch to Max.
With all heating calling, measure voltage across terminal 3 (black wire) and terminal 1 (blue wire) at connector H5 on the main PCB.
Mains voltage expected.
CH selector switch to Max.
With all heating calling, measure voltage across terminal 3 (black wire) and terminal 1 (blue wire) at connector H5 on the main PCB.
Mains voltage expected.
Isolate as per TOPs P4
and refit as necessary