Rinnai
Temperature Fluctuation / Hunting
Water temperature fluctuates between hot and cold during a 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
Flow rate below minimum activation, Pressure-balancing shower valve mixing cold water, Dirty flow sensor, Scale in heat exchanger
How to Fix / Troubleshooting
Safety first: Sudden temperature changes can cause scalding. Keep the set temperature moderate.
Steps to check:
- Increase flow: Open the hot water tap more to ensure flow is above the unit's minimum activation rate.
- Adjust shower valve: If using a pressure-balancing or thermostatic valve, set it to allow more hot water and avoid mixing too much cold.
- Clean inlet filter and flow sensor: Turn OFF water and power, clean the cold water inlet filter, and have the flow sensor inspected and cleaned if necessary.
- Descale if needed: Scale can cause unstable heating; schedule a professional descaling.
When to call a professional: If fluctuations persist, a technician should check flow sensor operation, gas modulation, and heat exchanger condition.
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Repair Difficulty
Medium
3/5
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