ATAG fault code C 20
Fault code C 20 on an ATAG boiler (including A-series and E-series) means: Flow sensor fault (e.g. open, short-circuited, out of range). 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 C 20 on an ATAG boiler indicates: Flow sensor fault (e.g. open, short-circuited, out of range).
Fixing fault code C 20: step by step
- Reset the appliance once; a one-off measuring error will then clear.
- Where you can reach it without opening the sealed combustion section, check that the sensor plug is seated firmly and the wiring is undamaged.
- If the code comes back, the sensor or its wiring is usually faulty (short or open circuit). Sensors in the sealed combustion section should be replaced by a qualified heating engineer.
Applies to
ATAG A-series, E-series, A203EC, A244C, A285C, A285EC, E22C, E264C, E264EC ALEC, E26C, E223C, E325EC CW5 with economiser.
Click a model for the parts list and exploded view of that appliance.
Fault code C 20 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:
- C 20 on A203C, A244CL, A244EC, Enigma, A203C / FGO … autom: LMUB, A244CL / FGO: Flow sensor fault.
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.
Based on the cause, these original ATAG parts fit (always check the type number of your appliance):
- Atag water trap pressure sensor € 33.98
- Atag water pressure sensor Huba € 139.98
- Atag connector outdoor sensor A € 21.75
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 C 20 mean?
flow sensor fault (e.g. open, short-circuited, out of range).
How do I fix fault code C 20 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 C 20?
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 C 20 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 →