IBC
Thermal Expansion / Overpressure
Boiler pressure rises significantly when heating and the relief valve occasionally discharges water.
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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
Failed expansion tank bladder, Overfilled system, Stuck fill valve, Blocked expansion tank connection
How to Fix / Troubleshooting
Safety: Allow the system to cool before working on the expansion tank or relief valve.
- Check cold pressure: When the system is cold, verify pressure is within the recommended range. If too high, drain some water.
- Test expansion tank: With the system depressurized, check the air charge at the Schrader valve on the expansion tank. If water comes out or no air is present, the tank has failed.
- Inspect fill valve: Ensure the automatic fill valve is not stuck open. Close any manual feed valves.
Replacing or recharging the expansion tank is often required and is best done by a heating professional.
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Repair Difficulty
Medium
3/5
Required Part
Expansion Tank
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