Boiler shows F.16 and shuts down, often with very high temperature readings

Safety first: Turn off power and allow the boiler to cool completely. Do not reset an overheat device on a hot boiler.

• Locate manual reset limit: Many Lochinvar boilers have a manual reset high limit thermostat on the heat exchanger or outlet piping. Once cool, press the reset button until it clicks.
• Check circulator and valves: Verify the primary pump is running and all valves are open. Correct any flow issues before restarting.
• Bleed air: Use air vents and bleed valves to remove trapped air from the boiler and near-boiler piping.
• Inspect heat exchanger: If overheating recurs, the heat exchanger may be scaled or restricted and should be inspected and flushed by a professional.

Professional help: Repeated overheat trips indicate a serious flow or control problem. Have a technician evaluate the system.