Nefit fault code H12
Fault code H12 on a Nefit boiler (including TopLine) means: The cylinder temperature sensor is defective. Its function is taken over by the boiler software. Reset the appliance once. If the code comes back, a part is usually faulty, often the burner control unit or PCB. 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 H12 on a Nefit boiler indicates: The cylinder temperature sensor is defective. Its function is taken over by the boiler software.
Applies to
Nefit TopLine, Aquapower HRC 25 CW4, Aquapower HRC 25 CW4 II, Aquapower HRC 25 CW5, Aquapower HRC 25 CW5 II, Aquapower HRC 30 CW5, Aquapower HRC 30 CW5 II, Aquapower HRC 45 CW6, Aquapower HRC 45 CW6 II.
Matching parts
Nefit 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 Nefit-series: ProLine (NxT) · TrendLine (II) · EcomLine · TopLine.
Based on the cause, these original Nefit parts fit (always check the type number of your appliance):
- Nefit burner control unit UBA 3.5 for TopLine € 279.66
- Nefit PCB for 3-way valve (TopLine) € 73.18
- Nefit control panel PCB 74594 for TopLine € 320.17
Further reading on this cause
Other Nefit codes with the same cause
- H11 — The domestic hot water outlet temperature sensor is defective. Its function is taken over…
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 Nefit boiler fault code H12 mean?
The cylinder temperature sensor is defective. Its function is taken over by the boiler software.
How do I fix fault code H12 on a Nefit 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 Nefit fault code H12?
That depends on the exact cause. In the Nefit parts overview at Instalpunt you will find the current price and stock for each part.
Can I fix fault code H12 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 Nefit boiler faults and codes at a glance →