084B8520 by Danfoss

The 084B8520 electronic climate controller is manufactured by Danfoss within the Electronic Climate Controllers series. Designed for DIN-rail or panel cavities, this microcontroller supervises compact refrigeration racks and single-zone HVAC systems by sequencing compressors, controlling evaporator fans, and issuing alarms. In industrial automation, it functions as a decentralized temperature regulator that sustains setpoint accuracy, initiates timed defrost cycles, and exchanges operating data with supervisory controllers, thereby reducing manual intervention in cold rooms, display cases, and process chillers.

The controller operates from a single-phase supply of 230 V, and its circuitry draws only 2.5 VA; this low demand eases the design of UPS or battery-backed panels. Electromechanical output relays are fitted, and the total of 4 permits direct switching of solenoid valves, condenser fans, or lighting without auxiliary contactors. Fieldbus communication is provided through MODBUS, while an optional LON transceiver can be installed for building-wide integration. Internal logic sequences up to 2 compressors, balancing runtime to equalize wear and providing automatic capacity reduction during part-load operation.

Installation weight stays low because the enclosure is only 0.26 kg. Evaporator supervision is limited to 1 coil, which matches single-circuit reach-in or walk-in fixtures found in retail and food processing. An integrated alarm output delivers a dry-contact signal when temperature limits are exceeded, sensors fail, or doors remain open, enabling immediate local or remote notification. Temperature measurement flexibility is provided by support for NTC-M2020; PTC 1000; Pt 1000 probes, so thermistor or platinum resistance elements can be used to achieve the required accuracy and response time.