|Heating mode active||– Permanently on: Heat demand, heating mode
– Flashing: Burner on in heating mode
In System boilers and open Vent boilers – Permanently on means there is a heat demand being requested by the radiators/ufh/zone heating or from hot water zone. This usually kicks in several seconds after the programmer is switched on the relay in the zone valve has activated and therefore a signal is sent for the boiler to begin to fire up. When flashing it means the burner is now on and sending heat down the pipes to where it is requested.
In Combi Boilers / Storage Combis – Permanently usually means there is a heat demand being requested by the radiators. Flashing means the burner is on and sending heat down the pipes.
Where the Combi is being used in a hybrid system setup, similar manner to a System boiler, the same principle applies as that of the System Boiler request, ie radiator symbols means any zone that is requesting heat.
If this symbol is not coming on. It means no control signal is being sent by the heating controls or by the zone valves.