Vaillant boiler has the following heating modes;
S0 No heat demand
S1 Fan running
S2 water pump running
S3 Ignition Seq
S4 Burner ignited
S5 Fan and pump running
S6 Fan over run
S7 Pump over run
S8 Anti cycling mode
Just had my central heating system;
1) Changed from open vent to sealed...
