Display shows A11, furnace does not start, may be associated with external safety devices

Safety: Disconnect power. Identify all external safety devices wired to the Beretta furnace (e.g., high-limit stats, smoke stats, external emergency stop).

• Check emergency stop: Ensure any external emergency stop switch is in the RUN position.
• Inspect safety thermostats: Locate external high-limit or smoke thermostats in the flue or ductwork. Check for manual reset buttons and press them after the system has cooled.
• Check wiring continuity: Follow the safety loop wiring from the furnace to each device, looking for loose connections or damaged cables. Tighten terminals as needed.

If A11 remains and all external safeties are reset, a technician should test the safety loop with a meter and verify control board operation.