External condensate pipe drips constantly or backs up, sometimes causing boiler lockouts in cold weather, with no specific error code displayed.

Safety first: Condensate is mildly acidic; avoid skin contact and wear gloves.

• Check external pipe: In freezing weather, look for ice on the external condensate pipe. If frozen, thaw gently with warm (not boiling) water and insulated cloths.
• Reset boiler: After clearing the ice, reset the boiler and observe its operation.
• Engineer checks:
  • Inspect and clean the internal condensate trap.
  • Ensure the condensate pipe is correctly sized and has an adequate fall.
  • Consider rerouting or insulating the pipe to prevent future freezing.