Set Appliance State:

Mains Power Off
On/Off Switch OFF
Set Multimeter to AC Volts Set meter to measure AC Volts
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Appliance On/Off switch On.
All heating controls calling.
Measure voltage across terminal marked CHR and terminal marked N on the main 12 terminal connector block below the control panel.