Atlantic
Boiler Not Responding to Room Thermostat
Boiler runs continuously and overheats the house even when the room thermostat is turned down or off.
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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
Room thermostat contacts stuck closed, Shorted thermostat wiring, Faulty PCB ignoring control input, Motorized valve stuck open
How to Fix / Troubleshooting
Safety: Overheating can waste energy and stress the system.
- Turn down controls: Set the room thermostat to minimum and ensure any programmers are set to OFF. If the boiler still runs, there is a control fault.
- Isolate heating: Use the boiler's mode selector to switch heating off (if possible) while keeping DHW on.
- Check thermostat location: Ensure the thermostat is not near a heat source or in direct sunlight, which can confuse control.
- Professional diagnosis: A technician should test thermostat circuits, zone valves, and PCB inputs, and replace faulty components.
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Repair Difficulty
Medium
3/5
Required Part
Room Thermostat or Motorized Zone Valve
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