Boiler displays A25, burner output limited, sometimes with noisy combustion

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

Possible Causes

Blocked condensate trap, blocked condensate pipe, incorrectly installed condensate siphon, negative pressure in drain

Safety: Isolate power. Condensate is mildly acidic; wear gloves and eye protection.

Check condensate outlet: Ensure the condensate pipe is not frozen, kinked, or blocked. Clear any obstruction.
Clean condensate trap: Remove the condensate trap/siphon as per the De Dietrich manual. Rinse thoroughly with clean water to remove sludge.
Re-prime trap: Fill the trap with clean water before refitting to ensure proper sealing.
Technician tasks: If the fault persists, a professional should check for flue gas recirculation and correct condensate routing.

Medium 3/5

Condensate Trap / Siphon

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