Boiler shuts down and displays error 10; unit may attempt to start but stops within seconds, sometimes with fan noise briefly heard.

Safety first: Turn off power to the boiler at the breaker and close the gas isolation valve before inspecting any venting. Allow the unit to cool fully.

• Check outdoor terminations: Inspect the flue exhaust and combustion air intake terminals outside. Remove any leaves, snow, bird nests, insect screens, or debris blocking the openings.
• Inspect vent pipes: From the boiler to the termination, visually check PVC/PP/metal vent pipes for sagging, disconnections, or signs of crushing. Ensure all joints are fully seated and properly glued or clamped.
• Verify clearances: Confirm that the exhaust and intake terminations meet Rinnai clearance requirements from walls, corners, windows, and other structures to avoid recirculation of flue gases.
• Check condensate in vent: Look for standing water or gurgling in the vent that may indicate improper slope or blocked condensate drain. Clear the condensate trap and ensure the vent slopes back to the boiler as specified.
• Reset and test: Restore power and gas, then reset the boiler according to the user manual. If error 10 reappears, stop using the boiler and contact a qualified Rinnai technician to perform a full combustion and venting inspection.