How to Reset a Vaillant Boiler

Where is the reset button on a Vaillant boiler?

On Vaillant ecoTEC boilers the reset button sits on the control panel beside the display. On many older models it carries a flame with a line through it rather than the word reset, and many Vaillant panels have no text on the buttons at all, so look for the symbol.

How long to hold it depends on the generation. Older ecoTEC plus instructions say to hold the reset button for about one second. On the current ecoTEC plus, reset shares a button with standby: a press of under three seconds switches standby on or off, and only a hold of more than three seconds resets. Holding for four or five seconds works on either. If you are unsure which button it is, the operating instructions for your model show the panel layout.

The reset button is on the outside of the boiler. You never need to remove the casing to reset a Vaillant, and you should not.

Check these before you press reset

A reset only clears the lockout. It does not fix whatever caused it, so a reset done without a check usually ends with the same code ten minutes later. Read the code on the display first, then work through the checks that match it; if the display is blank, a Vaillant that will not turn on at all is a power problem rather than a lockout.

• F28 or F29 (the burner will not light, or lit and went out): check the gas. Try the hob. If you are on a prepayment meter, check the credit and top up. Make sure the gas cock on the pipe under the boiler is open, with its handle in line with the pipe.
• F22 (low water pressure): top up the pressure through the filling loop first. Vaillant recommends at least 1 bar, and 1.5 bar is a good cold reading. The boiler usually clears F22 by itself once the pressure is back, with no reset needed.
• Condensate pipe: in freezing weather, check the plastic pipe running outside for ice. A frozen pipe is one of the most common reasons for an F28 in January.
• Power: if the display is blank, check the fused spur switch next to the boiler and the fuse box before anything else.

How to reset a Vaillant boiler step by step

With the likely cause dealt with, the reset itself takes a few seconds. The steps below are for the ecoTEC pro and ecoTEC plus, two of the most widely fitted Vaillant ranges.

• Note the fault code on the display. If you need to call someone later, they will ask for it.
• Press and hold the reset button, for about a second on older models or more than three seconds on current ones, then let go.
• The display should clear the code and show the pressure or the flow temperature again.
• Turn on a hot tap, or turn the thermostat up, so the boiler has a reason to fire; if the radiators heat but the tap stays cold, see Vaillant heating works, no hot water.
• Give it two minutes. The fan runs first, then you should hear the burner light with a soft whoosh.
• If the code comes straight back, stop and read the section below before you reset again.

Vaillant F28: why you get three resets, not ten

F28 means the flame signal was not detected during the ignition phase. By the time you see it, the boiler has already tried to light on its own and failed: three attempts on the 2015-era ecoTEC plus, five on the current model, according to the operating instructions. Those instructions put a hard limit on what you should do next: check the gas stopcock is open, press reset, and repeat that at most three times. If the fault is still there, the instruction is to contact a competent person.

The limit exists for a reason. Every failed ignition puts wear on the ignition electrode and the gas valve, and a boiler that keeps failing to light has a fault that needs finding, not clearing. Resetting again and again can turn a cheap repair into a more expensive one. Our page on the Vaillant F28 code explains the causes in more detail, and Vaillant F29 covers the related fault where the flame lights and then goes out.

If you can smell gas at any point, do not press reset. Open windows, turn off the gas at the meter if you can reach it safely, do not touch any switch, then leave the property and call the National Gas Emergency Service on 0800 111 999.

Codes you should not keep resetting

Some Vaillant codes point to faults that a reset can hide for a while but never fix. If you see any of these more than once, leave the boiler off and book an engineer.

• F20: the overheat thermostat has tripped. Often a pump or a blockage, and running the boiler again risks damage to the heat exchanger.
• F61 and F62: faults on the gas valve or its control. These are not household checks.
• F75: the boiler cannot detect the pressure rise when the pump starts, a pump or pressure sensor fault once low pressure and air are ruled out.
• Any code that returns within an hour of a successful reset, whatever it is.

What an engineer does after a failed reset

For an F28 that will not clear, a good engineer checks the gas first: the working pressure at the boiler’s gas valve under load, which shows whether the meter, the pipe run or the valve is the bottleneck. Then they look at the ignition electrode and its gap, the lead and the earth, the condensate trap and the fan. The fix for an F28 is commonly one of four things: an electrode, a gas valve, a blocked condensate trap or a board.

As a guide to what these parts typically cost in the UK market with fitting, an electrode is often £80 to £200, a gas valve often £200 to £400 and a printed circuit board often £350 to £700. These are typical market ranges, not our prices. When you book a Vaillant boiler repair with us you pay the £60 call-out, and the repair price is agreed with you on site before any work starts. Gas work is carried out by Gas Safe registered engineers.