ATAG fault code 40
Fault code 40 on an ATAG boiler (including I-series) means: Temperature exceeded at the burner flow temperature sensor. Reset the appliance once. If the code comes back, a part is usually faulty, often a temperature sensor. You can check the water pressure and settings yourself; leave work on gas-carrying parts to a certified gas engineer.
After a safety alert (gas, flue gas, combustion), reset no more than once and call in a certified gas engineer. If you smell gas, call your national gas emergency number or 112 immediately.
Cause
Fault code 40 on an ATAG boiler indicates: Temperature exceeded at the burner flow temperature sensor.
Applies to
ATAG I-series, i20EC CW3.
Fault code 40 on other ATAG series
The same code does not mean the same thing on every series. Check the rating plate to see which series you have:
- 40 on I-series, i20EC CW3: Open circuit or short circuit of the burner flow temperature sensor.
- 40 on I-series, i32S: Internal fault.
- 40 on I-series, i36C CW5: Internal data fault.
- 40 on I-series, i28C CW4: Boiler block temperature limiter has been activated.
- 40 on I-series, i36EC CW5 with economiser: Flame is detected although the appliance is switched off.
- 40 on I-series, i28EC CW4 with economiser: Flame is not detected.
Matching parts
ATAG parts are available from Instalpunt; shipping to EU countries from €12.95 (€16.95 for more distant countries), usually 3–5 working days.
Parts per Atag-series: A Series · i Series (iCon) · Q Series · E Series · P-series (iCon) · Blauwe Engel · XL-series.
For fault code 40, the part involved is usually in the category: burner.
Based on the cause, these original ATAG parts fit (always check the type number of your appliance):
- Atag flue gas sensor € 62.95
- Atag flow sensor € 59.95
- Atag water trap pressure sensor € 34.95
Further reading on this cause
Other ATAG codes with the same cause
- 10 — Outdoor sensor fault (e.g. open, short-circuited, out of range)
- 102 — Pressure sensor defective
- 110 — Flow sensor fault (e.g. open, short-circuited, out of range)
- 112 — Return sensor fault (e.g. open, short-circuited, out of range)
- 114 — Outdoor sensor fault (e.g. open, short-circuited, out of range)
- 20 — Flow temperature sensor defective
Fix it yourself or call an engineer?
Always consult the manual for your appliance and work safely. If in doubt or if the fault comes back, call in a qualified professional. A question about a part? Write to us at info@instalpunt.nl.
Frequently asked questions
What does ATAG boiler fault code 40 mean?
Temperature exceeded at the burner flow temperature sensor.
How do I fix fault code 40 on an ATAG boiler?
First check the cause described above. Then restart the appliance using the reset button. If the message comes back, a part usually needs replacing or the fault needs to be repaired by a qualified professional.
Which parts do I need for ATAG fault code 40?
That depends on the exact cause. In the ATAG parts overview at Instalpunt you will find the current price and stock for each part.
Can I fix fault code 40 myself?
You can reset the appliance and check things like the water pressure or settings yourself. Work on gas-carrying parts must be left to a certified gas engineer.
All ATAG boiler faults and codes at a glance →