Boiler shows A13, burner output limited or locked out, often in condensing operation

Safety: Condensate is mildly acidic. Wear gloves and eye protection when handling.

• Check external condensate pipe: In cold weather, ensure the plastic condensate discharge pipe from the Hoval boiler is not frozen. Thaw gently with warm (not boiling) water or warm towels.
• Clean condensate trap: Remove the trap beneath the heat exchanger, empty it, and rinse with clean water. Remove sludge or debris. Refill with water before refitting to maintain the water seal.
• Check pipe fall: Ensure the condensate pipe has continuous fall to the drain and no upward loops that could trap water.
• If the boiler has a condensate level sensor, check its wiring and clean the sensor probe if contaminated.