Error 301 displayed, furnace overheats and shuts down, casing feels very warm.

Safety: Overheating can damage the furnace. Turn off power and allow the unit to cool before touching any components.

• Check system water pressure: On hydronic Ariston furnace/boiler units, verify the pressure gauge reads within the recommended range (typically 1.0–1.5 bar when cold). If low, top up via the filling loop according to the manual and bleed radiators.
• Ensure circulation: Confirm that at least some radiators or air handlers are open and calling for heat. Fully closed valves can cause rapid overheating.
• Inspect circulation pump: With the front panel removed, locate the Ariston circulation pump. Listen for operation when there is a heat demand. If silent or excessively hot to touch, the pump may be seized.
• Clean system filter: If a magnetic or mesh filter is installed on the return line, isolate it and clean out sludge and debris.
• Reset overheat thermostat: Some models have a manual reset overheat stat on the heat exchanger. Once cooled, press the reset button if accessible. If it trips repeatedly, a professional must diagnose the root cause.