Servicing an ATAG boiler and reading its codes

Which ATAG boilers you’re likely to have

ATAG sells combi and solo boilers in a handful of series, each with a user manual on its documentation page: the A-Serie (A20 to A28), the E-Serie, the i-Serie (i20, i28 and i36 in C, EC, CZ and ECZ versions, plus the i32S solo), the Q-Serie with a built-in hot-water store, and the P-Serie for flats and VvEs.

What they share is a stainless steel (RVS) heat exchanger, which ATAG says doesn’t corrode or wear. ATAG offers up to 15 years’ warranty on it if the boiler was installed by an ATAG SelectDealer; your warranty card says whether that applies to yours.

How often ATAG says to service it

ATAG gives more than one answer:

• Its consumer FAQ says once a year by an experienced installer.
• The installation manuals for the i-Serie (2018 edition) and the A-Serie advise a yearly inspection or service, but at minimum an inspection every two years and a full service every four, depending on the running hours in the warranty conditions.
• The P-Serie brochure prescribes an inspection every two years and a full service every four.

An inspection is checks and measurements; a service is the boiler opened up and cleaned. The manual’s practical clue for which you need is how dirty the siphon is, which ATAG calls an important indication that maintenance is due.

What an ATAG service involves

I follow the manufacturer’s steps for the boiler in front of me. For an i-Serie the installation manual sets them out:

1. Casing off. On an ATAG it’s also the air box, so it gets wiped clean.
2. Siphon out, rinsed, O-ring checked and greased, refilled with 150 ml of water. A leaking siphon is replaced whole.
3. Fan and burner cassette out. The cassette is checked for wear, dirt and cracks and cleaned with a soft brush and a vacuum, unlike an Intergas, where the manual says to leave the burner alone.
4. New gaskets between burner and top box and between top box and heat exchanger, plus new sealing rings on the gas pipe. ATAG’s rule is to replace the gaskets of every part taken off, which I do on every make; boiler servicing explains why.
5. Venturi, fan and heat exchanger checked and cleaned with a soft brush and a vacuum; ATAG says the exchanger must not be flushed with water from above. The ignition electrode is replaced if its pins are worn.
6. Back together and checked, with leak-detection spray on the gas-carrying parts and a flue gas analysis.

Pressure and topping up on an ATAG

On an i-Serie the display shows the pressure by default; on an A or E-Serie you press the i-key until it shows A6. ATAG says it should be between 1.5 and 1.7 bar with the system cold, and the boiler tells you when it isn’t:

• 118 with a spanner: too low. Below 1.0 bar the output is cut by 20 percent; below 0.7 bar the boiler stops.
• 117 with a spanner: too high, above 3.0 bar. The boiler stops. Let some water out.
• 105 with a spanner: after topping up from below 0.7 bar, a de-aeration programme of about 7 minutes. Not a fault; reset does nothing.

Top up slowly through the fill-and-drain valve to 1.5 to 1.7 bar, bleed from the lowest point and check again; ATAG’s FAQ on topping up points to its YouTube channel. Needing to top up more than once after a fresh fill is a leak: see my guides to boiler pressure, the expansion vessel and a leaking boiler.

Reading an ATAG fault code

ATAG doesn’t publish a code list for consumers. Its help page for faults says your installer is the first point of contact and that ATAG doesn’t take fault reports from consumers. The codes are in the manual for your series: plain numbers on the i-Serie, while on the A and E-Serie the pressure codes appear as c1 05, c1 17 and c1 18.

A spanner next to the code means a blocking, a temporary condition that clears itself or, after several attempts, locks the boiler out. A bell means an error: the boiler has locked out and needs a reset and, if that doesn’t hold, an engineer. ATAG’s advice is to try a reset and, if the fault persists, call your installer with the number. My rule is one reset.

The i-Serie manual lists, in ATAG’s words:

• 10, 20, 40, 50: sensor fault on the outdoor, flow, return or hot-water sensor
• 105: de-aeration programme running
• 110 / 111: safety or maximum temperature exceeded
• 117 / 118: pressure too high or too low, or the pump’s pressure rise too high or too low
• 129: the fan doesn’t start
• 133: no flame after five ignition attempts

The E-Serie user manual (2015) lists only the pressure codes; for the rest, download your series’ manual from ATAG’s documentation page. Send me a photo of the display with the symbol visible; boiler repair explains how a visit works.

ATAG’s rules on water quality

ATAG is strict about what goes into the system, and the warranty depends on it. The i-Serie manual says to fill with drinking water, that groundwater, demineralised and distilled water are not allowed, and that the warranty lapses if the system wasn’t flushed or the fill water doesn’t meet ATAG’s specification. The E-Serie manual adds that antifreeze and corrosion inhibitors are not permitted. With water harder than 15°D the plate heat exchanger needs descaling more often, and a scaled-up one isn’t covered. So I add nothing to the water.

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. ATAG puts an average boiler’s life at 15 to 20 years; if yours is getting there, 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.