Burner controls, ignition and flame safeguards
Nu-Way XGN 450-3000 MBC Microprocessor Burner Control fault codes
What all 16 Nu-Way XGN 450-3000 MBC Microprocessor Burner Control 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 |
|---|---|---|
| 20H | 20H The air pressure switch is not in the rest position, which prevents the burner from starting. | RED |
| 21H | 21H The air pressure switch has failed, which prevents the burner from operating. | RED |
| 22H | 22H The gas pressure switch has failed, which prevents the burner from operating. | RED |
| 25H | 25H The burner locks out because no flame was established after the safety period ended. | RED |
| 26H | 26H The burner locks out because extraneous light was detected inside the combustion chamber. | RED |
| 27H | 27H The burner locks out because the flame failed while the system was in normal operation. | RED |
| 2BH | 2BH The burner locks out because there is a short circuit in the photoresistor flame sensor. | RED |
| 43H | 43H The burner locks out because the system detected a leak in the first gas valve. | RED |
| 44H | 44H The burner locks out because the system detected a leak in the second gas valve. | RED |
| 66H | 66H The burner stops because there is a fault with the gas servomotor or the coding plug. | RED |
| 68H | 68H The burner stops because the system detected an acknowledgement fault with the air servomotor. | RED |
| 69H | 69H The burner stops because the system detected an acknowledgement fault with the gas servomotor. | RED |
| 6AH | 6AH The burner stops because the air motor position has moved out of its acceptable tolerance. | RED |
| 6BH | 6BH The burner stops because the gas motor position has moved out of its acceptable tolerance. | RED |
| 6EH | 6EH The burner will not start because the motors have been interchanged or incorrectly connected. | RED |
| 6FH | 6FH The burner stops because either the gas or air servo motor is unable to find its reference positions. | RED |
Every code comes from the manufacturer's own manual. Subscribers see which manual and page.