Burner controls, ignition and flame safeguards
Kromschroder BCU 46x / 480 Burner Control Unit fault codes
What all 21 Kromschroder BCU 46x / 480 Burner Control Unit fault codes mean, in plain words, with a risk grade for each. These come from the manufacturer's own manual. The fix for each one is in WERCS Diagnose.
Get the fixes · plans from $49/moUpdated July 23, 2026
| Code | What it means | Risk |
|---|---|---|
| 51 | Blinking 51 A signal interruption occurred at the safety interlock or emergency stop, shutting down the burner. | RED |
| 53 | Blinking 53 The time between two starts is less than the minimum allowed, preventing the burner from firing. | GREEN |
| Ot | Ot The ambient temperature is too high for the control unit, stopping operation until it cools down. | GREEN |
| Ut | Ut The ambient temperature is too low for the control unit, stopping operation until it warms up. | GREEN |
| E 02 | Blinking E 02 The burner locks out because no flame was established by the end of the first safety time during startup. | RED |
| E 04 | Blinking E 04 The burner locks out because the flame signal fell below the switch off threshold during normal operation. | RED |
| E 05 | Blinking E 05 The burner locks out because an incorrect extraneous flame signal was detected before the second burner ignited. | RED |
| E 08 | Blinking E 08 The burner locks out because the second burner experienced a flame failure during operation or delayed controller enable. | RED |
| E 11 | Blinking E 11 The first burner had more than five restarts within fifteen minutes, which locks out the burner. | RED |
| E 32 | Blinking E 32 The burner locks out because the supply voltage is out of range or there is an internal device error. | YELLOW |
| E 40 | Blinking E 40 The burner locks out because the tightness test detected a leak in the first gas solenoid valve. | RED |
| E 41 | Blinking E 41 The burner locks out because the tightness test detected a leak in a downstream gas solenoid valve. | RED |
| E 44 | Blinking E 44 The system detected a faulty pressure switch signal, which prevents the burner from operating. | RED |
| E 80 | Blinking E 80 An error occurred in the flame amplifier for burner one, causing the burner to lock out. | RED |
| E c1 | Blinking E c1 The valve closure is not confirmed during standby, preventing the burner from starting up. | RED |
| E c8 | Blinking E c8 The system failed to confirm that the proof of closure switch is open, locking out the burner. | RED |
| E d0 | Blinking E d0 A high air pressure signal is present before the fan turns on, meaning the no flow state failed and the burner control stops operating. | RED |
| E d1 | Blinking E d1 The air monitor failed to switch after the air supply activated, causing the burner to lock out. | RED |
| E dP | Blinking E dP The air pressure switch input signal dropped out during the pre purge cycle, which causes the burner control unit to fault. | RED |
| E d2 to E d8 | Blinking E d2 ... E d8 (digit = program step 02 to 08) The air supply failed during startup or operation, causing the burner to shut down immediately. | RED |
| E u1 to E u9 | Blinking E u1 ... E u9 (digit = program step) The minimum gas pressure monitoring signal dropped out during a specific program step, which locks out the burner. | RED |
Every code comes from the manufacturer's own manual. Subscribers see which manual and page.