F.387 — Burner in fault state: Ground fault in ionization current

What does F.387 mean?

The burner is in a fault state due to a ground fault in the ionization current, or a faulty BCU burner control unit. Condensate backup can also cause this issue.

• Condensate backup in the system (drain, siphon trap)
• Damaged insulation blocks, electrodes, or flame body assembly due to water
• Faulty ionization electrode or connecting cable
• Faulty BCU burner control unit

Click steps to track your progress.

1. 1

   Check the condensate drain and siphon trap for blockages or backup.

2. 2

   Inspect the ionization electrode and connecting cable for damage or moisture if no condensate issue is found.

3. 3

   Reset the boiler by briefly turning off and on its power supply. If the fault persists, contact a qualified heating engineer.