Set Appliance State:

Mains Power Off
CH Demand
Gas On
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

All heating controls calling.
Allow appliance to ignite and run and system to heat.
Observe system pressure gauge.
Does the system pressure remain stable at its charged pressure?
System should be charged at approximately 1.5 bar.