Viessmann
Inefficient Combustion / Heat Loss
Water heater runs but gas consumption seems unusually high
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Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
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Possible Causes
Incorrect combustion settings, Scaled heat exchanger reducing efficiency, Constant small hot water draws causing cycling, Heat loss in long uninsulated hot water pipes
How to Fix / Troubleshooting
Safety: Combustion tuning must be done with proper instruments by a qualified technician.
- Check usage patterns: Avoid frequent very short hot water draws that cause repeated ignition cycles.
- Insulate pipes: Insulate long hot water runs to reduce heat loss and unnecessary reheating.
- Descale heat exchanger: Clean the plate and primary heat exchangers to restore efficiency.
- Professional combustion check: Have a Viessmann-trained technician perform a combustion analysis and adjust gas valve and fan settings to factory specifications.
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Repair Difficulty
Hard
4/5
Required Part
Primary Heat Exchanger
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