Set Appliance State:
On/Off Switch OFF
Set Multimeter to AC Volts 
CH Demand
Isolate Mains Power to appliance as per TOPs P4
Ensure DHW storage cylinder is up to temperature
Gain access to PCB as necessary
Ensure DHW storage cylinder is up to temperature
Gain access to PCB as necessary
| WARNING! - Mains voltage is expected during test follow TOPs P4 live testing procedure |
Measurement:
Appliance On/Off switch On.
Reset lockout as necessary.
All heating controls calling.
Measure voltage across connection 2 (black wire) and
connection 3 (blue wire) at connector J7 at the PCB.
Reset lockout as necessary.
All heating controls calling.
Measure voltage across connection 2 (black wire) and
connection 3 (blue wire) at connector J7 at the PCB.
Isolate as per TOPs P4
and refit as necessary