Verified boiler fault code
Viessmann OC Fault Code (Vitodens fault-code checker row)
Insufficient power supply.
Safety disclaimer
Fault code summary
- Manufacturer
- Viessmann
- Fault code
- OC
- Fault type
- Electrical
- Severity
- Not specified
- Reset
- Not specified
- Applicable models
- Vitodens 100-W
Quick answer
Insufficient power supply.
What does this fault code mean?
Insufficient power supply.
Common causes
- Insufficient power supply.
Symptoms
- Burner blocked.
What can the homeowner safely check?
- Check only that the boiler has electrical power; use a qualified electrician for supply diagnosis.
Boiler reset information
Reset information was not provided in the verified manufacturer source. Do not repeatedly reset an unresolved fault.
When should I call an engineer?
Contact a suitably qualified heating engineer when the fault persists, the boiler locks out, or the manufacturer instructions do not resolve it. For gas appliance work in the UK, use a Gas Safe registered engineer.
Engineer diagnosis
- Assess the electrical supply and boiler electrical circuit.
Applicable boiler models
Related fault codes
No related verified fault codes are available for this range.
Manufacturer documentation
Viessmann UK Fault CodesFault Code OC | Vitodens 100-W | Burner blocked | Insufficient power supply
Last verified
2026-09-12
Frequently asked questions
What does Viessmann OC mean?
Insufficient power supply.