A17
Hoval Safety interlock circuit open

Furnace shows safety chain open / safety loop error, burner inhibited

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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

Tripped safety temperature limiter, Open flue gas thermostat, Faulty emergency stop switch, Loose wiring in safety loop on Hoval control panel

How to Fix / Troubleshooting

Safety: Do not bypass safety devices. Identify and correct the cause.

  • Check emergency stop: Ensure any external emergency stop or boiler room safety switch is reset and latched.
  • Inspect safety thermostats: Locate the STB and flue gas thermostat. If they have manual reset buttons, press them once after the system has cooled.
  • Check wiring: Open the Hoval control panel and visually inspect the safety loop terminals for loose or broken wires. Tighten as needed.
  • Reset controller: After confirming all safety devices are intact and reset, clear the error and test operation.
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Repair Difficulty

Medium 3/5

Required Part

Safety Temperature Limiter (STB)
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