Honeywell Gas boiler control unit S4561B1039U(2)

The Honeywell S4561B1039U(2) is a PCB-type burner control unit designed for automatic ignition and flame supervision of atmospheric gas burners in wall-hung boilers, complying with EN 298. It operates at 220–240 V AC, 50 Hz, with a power consumption of 10 W. The unit uses ionisation flame detection and provides spark ignition at 5 Hz with a minimum open spark voltage of 15 kV. It features a safety timer setting of 0 s, supports external reset and high-limit alarm, and includes non-volatile blocking and alarm in absence of heat. The PCB dimensions are 105 mm with 4 mounting holes, and it fits Pegasus F2/F3 boilers.

Parts of this type are selected by matching the supply voltage, frequency, and flame detection method (ionisation) to the boiler's control system. The PCB dimensions and mounting hole pattern must align with the boiler's enclosure. The gas valve current rating (up to 1 A) and connector type must be compatible. Always verify the specific model compatibility with the boiler make and model before ordering.

Common failures include loss of flame detection due to a faulty ionisation probe or wiring, leading to repeated ignition attempts or lockout. Spark ignition may fail if the spark electrode gap is incorrect or the high-voltage cable is damaged. The unit may also fail to start if the safety timer or self-check sequence is interrupted by a faulty sensor or valve. Check for visible damage, loose connections, and correct grounding.