Intergas Over-Pressurization / Expansion Vessel Failure

Boiler pressure rises rapidly when heating, relief valve 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 vessel diaphragm, Expansion vessel lost charge, Faulty pressure relief valve, Filling loop left open

How to Fix / Troubleshooting

Safety first: Allow system to cool. Water from the relief valve may be hot.

Steps:

  • Check filling loop: Ensure the filling loop valves are fully closed and the flexible hose is removed if required by local codes.
  • Check expansion vessel charge (technician): Isolate the boiler from the system and drain pressure to zero. Measure the air charge at the expansion vessel Schrader valve and recharge to the value specified by Intergas (often around 0.8–1.0 bar).
  • Inspect relief valve: If the pressure relief valve has discharged repeatedly, it may not reseat properly and should be replaced.

If the expansion vessel bladder is ruptured (water from Schrader valve), the vessel must be replaced.

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Repair Difficulty

Hard 4/5

Required Part

Expansion vessel
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