Nibe
Unstable Outlet Temperature / Mixing Valve or Control Issue
Water heater’s hot water temperature fluctuates significantly during a single shower.
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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
Faulty thermostatic mixing valve, inconsistent cold water pressure, sensor lag or misplacement, external heat source cycling
How to Fix / Troubleshooting
Safety first: Sudden temperature spikes can cause scalding. Test with caution.
- Step 1 – Check mixing valve:
- Exercise the thermostatic mixing valve and ensure it is not partially blocked by debris.
- Step 2 – Compare taps:
- Test multiple hot outlets; if only one is affected, the issue may be local to that mixer or shower valve.
- Step 3 – Verify cylinder temperature stability:
- Monitor the Nibe display; if tank temperature is stable while outlet fluctuates, focus on mixing valves and plumbing.
Replace the thermostatic mixing valve if it cannot maintain a stable outlet temperature.
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Repair Difficulty
Medium
3/5
Required Part
Thermostatic Mixing Valve
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