UK & Europe
Vaillant error codes
Vaillant ecoTEC gas boilers show a fault as the letter F and a number, written with a dot: F.22 or F.28. The newest ecoTEC plus boilers add a zero, so F.28 becomes F.028. The codes and their meanings here come from Vaillant's UK fault code list and its ecoTEC manuals.
- 8 codes
- Boilers
- Checked against official pages
Boilers 8 codes
F22 Low water pressure
The water pressure in your heating system has dropped too low, so the boiler has shut down for now.
F28 No flame detected when lighting
The boiler tried to light but didn't detect a flame, so it has locked out.
F29 Flame went out and won't relight
The flame went out while the boiler was running, and it couldn't light again.
F75 No pressure rise when the pump starts
When the boiler's pump started, the pressure didn't change as much as it should.
F20 Overheat: safety cut-out tripped
The flow or return water temperature went over the maximum limit, so the safety cut-out has shut off the gas valve.
F23 Flow and return temperatures too far apart
The water leaving the boiler is much hotter than the water coming back to it.
F27 Flame detected with the burner off
The boiler sensed a flame when the burner should have been off.
F62 Flame went out too slowly
When the boiler shut off the gas, it detected the flame going out later than it should have.
No codes of that type for this brand.
Good to know
- Resetting: on older ecoTEC plus and ecoTEC pro boilers, press the fault clearance key for one second. The 2023 ecoTEC plus manual says to hold the reset button for more than three seconds. Vaillant's manuals allow three attempts at most.
- If the boiler doesn't come back on after a reset, or the code is still there, Vaillant says to call a Gas Safe registered engineer. Needing to reset it regularly isn't normal either.
- Pressure: Vaillant's ecoTEC plus and ecoTEC pro manuals ask for 1.0 to 2.0 bar with the system cold.
- If you smell gas, leave the property straight away and call the National Gas Emergency Service on 0800 111 999.
Official help pages
- Vaillant: boiler fault codes list
- Vaillant: understanding an F28 fault code
- Vaillant: how to thaw a frozen boiler condensate pipe
- Vaillant: what to do if your boiler has no pressure
Every code page links the exact pages it was checked against. Last reviewed September 2026.