Boiler displays F.09, will not start, often after wiring changes or lightning

Safety first: Disconnect power before touching the control board or wiring.

• Power cycle: Turn off power at the service switch for at least 60 seconds, then restore. Sometimes transient faults clear with a full power reset.
• Inspect board and connections: Remove the control panel cover. Look for burnt components, discoloration, or bulging capacitors on the Lochinvar control board. Check all plug-in connectors for secure seating.
• Check grounding: Verify the boiler chassis is properly grounded and that the neutral and ground connections are tight. Poor grounding can cause control faults.
• Surge protection: If the fault followed a storm or power event, consider adding a surge protector to the boiler circuit after repair.

Professional help: F.09 typically requires control board diagnostics and replacement by a qualified technician. The replacement board must be programmed/configured per Lochinvar instructions for your specific model and gas type.