Servicing a Vaillant and reading its F-codes

Which Vaillant boilers you’re likely to have

Vaillant’s current range on its Dutch site is two boilers. The ecoTEC plus, its best-seller, comes as a combi (VHR 20/26, 25/32, 30/36 and 35/40), a heating-only solo (VHR S 25 and 35) and the VHR I 36 with a built-in 25-litre hot-water store. The ecoTEC exclusive is the top model, in VHR 25/36CF and 34/43CF, both CW5, with ExtraCondens, which uses heat left in the flue gases to preheat tap water.

For servicing, two things matter. IoniDetect combustion control recognises different kinds of gas and adjusts the combustion itself. And the boiler is built to be opened: the ecoTEC plus has side panels that come off separately, and on the exclusive Vaillant says every part is reachable from the front.

How often Vaillant says to service it

Vaillant’s advice pages on the life of a boiler and a boiler with no hot water recommend a yearly service by a certified installer. Its maintenance contracts run on a two-year cycle: Essential Care covers a service every two years with consumables, and the Smart and Complete tiers add remote support, labour and parts. Both statements are Vaillant’s; your manual and warranty conditions decide.

Vaillant puts a boiler’s life at 12 to 15 years, depending on the type, the maintenance, how often it switches between heating and hot water, and the water, since hard water and chemical contamination damage components.

What a Vaillant service involves

Vaillant describes a maintenance visit as a visual and safety check, cleaning of the parts that have got dirty, checking and adjusting the settings, testing heating and hot water, checking the combustion, the flue and the air intake, and checking that thermostat and boiler work together.

I follow the service instructions in the manual for your model. The gaskets of every part I take off are replaced, as on every make; boiler servicing explains why. The pressure, the expansion vessel and the pressure relief valve are checked, and the combustion is measured at the flue so I know the boiler is burning cleanly, whatever IoniDetect has settled on.

Pressure and topping up on a Vaillant

Vaillant gives slightly different figures on different pages. Its guide to topping up says stop between 1.5 and 2.0 bar and never go above 2.5. Its page on pressure that’s too high calls 1 to 1.5 bar normal with the system off, a little higher when running but under 2.5. Your manual settles it.

Vaillant’s steps: let the boiler cool for 15 minutes, find the vulkraan (usually near the expansion vessel, with a red lever), connect the filling hose, open the tap slowly and then the lever, stop at 1.5 to 2.0 bar, close both and check again once warm. Once a year is normal, twice on an older boiler; monthly is a leak, and so is pressure that won’t rise. Pressure that’s too high points at overfilling, the pressure relief valve, the expansion vessel or sediment. My guides to boiler pressure, the expansion vessel and a leaking boiler cover where to look.

Reading a Vaillant F-code

Vaillant publishes an official list of its fault codes for consumers, with a page for the common ones. You’ll see a code written as F.22 or F22; Vaillant’s list uses the second. Its advice for every code is the same: don’t try to fix it yourself, because that can be dangerous, and contact a CO-certified installer. The codes, in Vaillant’s words:

• F.13: the cylinder temperature sensor is short-circuited
• F.20: the safety cut-out (SCO) has interrupted the control of the gas valve
• F.22: no or not enough water in the boiler, or the water pressure is too low
• F.23: the temperature difference between flow and return is too big
• F.25: the flue gas temperature is too high
• F.27: a flame signal was detected while the burner is off
• F.28: no flame signal was detected during ignition
• F.29: re-ignition after a flame loss during operation failed
• F.61: the ASIC or µControl isn’t working within its defined times
• F.62: the flame cut-off was detected late
• F.75: the pressure change is too low when the heating pump starts

Three are the ones I’m sent most:

• F.22 can be as simple as too little water, but Vaillant also lists the pressure sensor and its wiring, the pump, the filling solenoid and the internal expansion vessel. Top up; if the code stays, it needs an engineer.
• F.28 is an ignition failure. Vaillant’s causes range from a frozen condensate pipe to the ignition, the gas supply and the electronics, and it says plainly you can’t fix it yourself.
• F.75 points at the pressure sensor, the internal pump, low pressure, the internal expansion vessel or air. Vaillant says you can bleed and top up yourself; if it stays, call.

Send me a photo of the display and the pressure; boiler repair explains how a visit works.

Resetting a Vaillant, once

Vaillant’s page on re-igniting has you check first: no visible damage, radiators bled, no fault on the display and 1 to 1.5 bar cold. Then set the thermostat to 19 to 21°C and press the reset button, marked with a triangle, a crossed-out flame or a circular arrow. If it won’t ignite, Vaillant says call an installer. My rule is one reset: a boiler that locks out again has a fault inside, and resetting it ten times only hides it.

When to call me

A service is €145 incl. BTW plus materials. For a fault, it’s €114.95 incl. BTW per hour, with no call-out charge; a typical repair with a part comes to around €300-€400 incl. BTW. I agree the work and the cost with you before I start; all prices are on the prices page. I work by appointment, 08:00-16:00, seven days a week, not as a 24-hour service.

Message me on WhatsApp with a photo of the display, the model, the pressure and your postcode. If your ecoTEC is nearing the 12 to 15 years Vaillant gives it, what a new boiler costs sets out my guide bands, from €1,995-€2,495 incl. BTW, with a fixed quote after I’ve seen the installation.

If you smell gas, leave the property and call 0800 9009 from outside. If a CO alarm goes off or you suspect carbon monoxide, get everyone outside and call 112.