Furnace display shows high water pressure; safety valve may discharge water (hydronic models)

Safety: Turn off power. Be cautious of hot water discharge at the pressure relief valve outlet.

• Check pressure reading: Verify the system pressure on the IVT gauge. If it is above the recommended maximum (often 2.5–3 bar), do not continue operating the unit.
• Reduce pressure: When the system is cool, bleed water from a radiator air vent or a drain valve into a bucket until the pressure drops to the normal range.
• Inspect expansion vessel: Locate the expansion vessel (often red or grey, with a Schrader valve). If water comes out of the Schrader valve or the vessel feels completely waterlogged, the diaphragm has failed and the vessel must be replaced.
• Check fill valve: Ensure the manual filling loop or automatic fill valve is fully closed and not letting water in continuously.

Persistent overpressure requires professional service to test and replace the expansion vessel or pressure relief valve.