Alpha Overheating / Thermostat Runaway

Water is too hot; scalding at faucets even at low mixing valve settings.

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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

Stuck thermostat contacts, Miswired Alpha thermostat assembly, Failed temperature sensor, Mixing valve malfunction

How to Fix / Troubleshooting

Safety: Turn OFF power or gas immediately. Hot water can cause severe burns.

  • Lower setpoint: Reduce the temperature setting on the Alpha control panel or mechanical thermostat.
  • Test thermostats (electric): With power OFF, check that thermostats open when water is hot. Replace any that remain closed.
  • Inspect temperature sensor (tankless): Ensure the Alpha outlet sensor is properly attached and not shorted.
  • Check mixing valve: If an external thermostatic mixing valve is installed, verify it is adjusted correctly and not stuck.

Persistent overheating requires immediate professional service to replace faulty controls and verify safety devices.

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Repair Difficulty

Hard 4/5

Required Part

Thermostat Assembly
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