Set Appliance State:

Mains Power Off
CH Demand
CH Temp control set to 60°C
Gas On
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

As the system temperature gets near the set temperature (60°C), does the fan speed start to reduce?
Note.
To speed up the heating time of the system, reduce the heating circuit by shutting off some of the radiators.