Set Appliance State:

Mains Power Off
CH Demand
Selector switch to Water
Turn hot water flow rate down until water temperature is satisfied and burner switches off
Gas On
WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure
Mains Power On

Observation:

Allow CH to run and achieve a flow temperature of 75°C.
Remove CH demand.
Does fan continue to run after until flow temperature falls to approximately 65°C?