Set Appliance State:

Mains Power Off
CH Demand
Heating temperature selector to maximum
Hot water temperature selector to OFF
Programmer or selector switch set to heating and hot water
Gas On
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Allow boiler to fire and start to heat system.
Does system start to heat and boiler remain quiet?