Honeywell Control box MMI810.1 mod.55 0621320

The Honeywell MMI810.1 mod.55 control box (SKU 0621320) is an automatic burner control unit for two-stage forced draught gas or oil burners. It operates on 220–240 V supply voltage and consumes 10 W. The control box features a waiting time of 9 s, a pre-purge time of 20 s, a pre-ignition time of 15 s, and a safety time of 5 s. It supports flame detection via an ionization probe or infrared flicker detector, with a minimum current of 5 µA from the detector. The unit has a protection class of IP44 and weighs 0.35 kg, with a body made of non-flammable plastic.

Control boxes of this type are selected by matching the supply voltage, flame detector type, and timing parameters (e.g., pre-purge, safety time) to the burner's requirements. Installation involves mounting the control box in any attitude, connecting the wiring base according to the terminal diagram, and ensuring the flame detector cable length does not exceed the specified maximum. The air proving switch and other safety devices must be wired correctly, and the unit must be compatible with the burner's stage configuration (e.g., two-stage).

Common failure modes for this kind of control box include failure to start, lockout after repeated ignition attempts, or erratic operation due to faulty flame detection. Symptoms may include the burner not responding to a call for heat, the reset button tripping, or the program display showing an error code. Check the flame detector, wiring connections, and supply voltage, and verify that the air proving switch and safety timings are within specifications.