Set Appliance State:

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

Observation:

Allow boiler to run and heat CH system while monitoring the system pressure on the system pressure gauge.
Does the system pressure remain constant?
Notes:
1. System pressure should be approximately 1 bar.
2. If test passes do not turn off heating as the burner ramp up period is initiated on every heating demand and burner pressure above minimum is required for further tests.