Demirdöküm Combi Boiler F20 Error
Overheating — safety thermostat tripped
The water in the heat exchanger exceeded the safe temperature and the safety thermostat stopped the boiler.
What is error F20?
On Demirdöküm Combi Boiler units, code F20 means overheating — safety thermostat tripped. The water in the heat exchanger exceeded the safe temperature and the safety thermostat stopped the boiler.
Likely causes
- Radiator valves closed, poor circulation
- Pump seized or faulty
- Scale or sludge in the heat exchanger
Safe steps you can take
- Check that radiator valves are open.
- Check the water pressure.
- Let the boiler cool down and reset it once.
If it keeps happening the pump or heat exchanger needs service.
Video guide
An editor-approved video appears here. For now you can search YouTube.
Watch on YouTubeFrequently asked questions
Is error F20 dangerous?
Gas, water and electricity are involved, so take care. Only do the safe steps on this page and don't touch internal parts.
Is a reset enough?
One reset clears temporary causes. If the code comes back, the real cause remains — don't keep resetting.
How much does the repair cost?
It depends on the part. After diagnosis the service sends the price to your tracking link; nothing is done without your approval.
Is the repair guaranteed?
Services on the platform write the warranty for parts and labour on the service form, which is sent to you as a PDF.
Sources: tesisat.org — Kombi arıza kodları . Code meanings can vary by model; check your user manual.