ATAG fault code BL 12
Fault code BL 12 on an ATAG boiler (including Blauwe Engel and Enigma) means: Maximum Delta-T of flow and return sensor on domestic hot water (DHW) repeatedly exceeded Central heating system operation is still possible as normal during the lockout. 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 BL 12 on an ATAG boiler indicates: Maximum Delta-T of flow and return sensor on domestic hot water (DHW) repeatedly exceeded Central heating system operation is still possible as normal during the lockout. During the lockout the pump continues to run at minimum capacity.
Applies to
ATAG Blauwe Engel, Enigma, Q-series, CMA 350, CMA 352, CMA 650, CMA 652, CMA 950, CMA 952, CZA 350, CZA 352.
Fault code BL 12 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:
- BL 12 on 24/32Ci, 24C, 24Ci, 35Ci, 35S, Blauwe Engel II: Maximum temperature difference of flow and return sensor on DHW repeatedly exceeded. CH operation is normally possible during the lockout (LO). During the LO the pump continues to run at minimum capacity.
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 BL 12, the part involved is usually in the category: pump.
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 sensor hot water cylinder/return T2-3-8-9 € 38.05
- Atag flow sensor/DHW T1 12k ohm € 61.16
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 BL 12 mean?
Maximum Delta-T of flow and return sensor on domestic hot water (DHW) repeatedly exceeded Central heating system operation is still possible as normal during the lockout. During the lockout the pump continues to run at minimum capacity.
How do I fix fault code BL 12 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 BL 12?
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 BL 12 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 →