Smarter Heating & Hot Water

Vaillant Boiler Symbols

Complete guide to the symbols and display icons found on newer generation Vaillant boilers, including the ecotec series. Use this reference to understand what each symbol means on your Vaillant boiler display.

No Symbol Description and Explanation Models Applicable to
0 Current Flow temperature of heated water leaving the boiler heat exchanger All
1 Flame: Permanently on: Correct burner operation; Burner on New Ecotec
2 Display of the current burner modulation rate (bar graph display)
The bar graph will go up and down depending on the power level the boiler is firing at.		 New Ecotec
3 Flame: Permanently on: Correct burner operation; Burner on Older Ecotec
4 Flame with cross: Boiler is at lock out and will display fault code Older Ecotec
5 Display of the current filling pressure of the heating system (bar graph display)
The filling pressure must be in the mid range between the two dotted lines.
– Permanently on: The filling pressure is within the permitted range.
– Flashing: The filling pressure is outside of the permitted range
6 Heating mode active
– Permanently on: Heat demand, heating mode
6.1 Heating mode active
– Flashing: Burner on in heating mode
7 Hot water generation active
– Permanently on: In draw-off mode before burner is on
– Flashing: Burner on in draw-off mode
7.1 Hot water generation active
– Flashing: Burner on in draw-off mode
8 Hot water generation active
For VUI (Storage Combination) / VUW (Combination) boilers:
– Permanently on, burner is on: In draw-off mode
8.1 Hot water generation active
– Flashing: Burner on in draw-off mode
9 Hot water generation active
On VU (System / OpenVent) boilers:
– Permanently on: time slot activated for hot water generation
9.1 Hot water generation active
– Flashing: Domestic hot water cylinder is being heated, burner on
10 Maintenance / Service required
In the "Live monitor", you can read further information about the reason for the service
11 Summer mode active
Heating mode is switched off
Decrease the heating flow temp until it says off. Increase the flow temp to original value to turn heating back on.
12 Boiler anti-cycling time is active
This function is used to prevent frequent on/off operations, and therefore contributes to prolonging the life of your boiler. The symbol also appears if the boiler is in a waiting period.
13 Internal pump is running
14 Gas valve is activated
15 F.XX Fault in the boiler
Appears instead of the basic display. A plain text display explains the displayed fault code.
Example: F.10 Flow NTC short circuit.