Set Appliance State:

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

Observation:

Allow boiler to fire and heat system.
Remove demand by turning selector switch to CH - MIN position, allow burner to go out.
Turn selector switch to CH - MAX position.
Is there approximately a 3 minute delay before the burner relights?
Note:
It may be necessary to reduce heating load by turning off some radiators to reduce time taken for this test.