DANFOSS SRB3100

Core Technical Specifications

• Module Operating Power Supply: 24 VAC / 24 VDC dual universal power input
• Temperature Signal Input Channels: 2-channel NTC thermistor temperature sensor input (evaporator coil surface temperature, cold storage ambient air temperature)
• Pressure Signal Compatibility: Compatible with Danfoss MBS3100 series 4–20mA refrigeration pressure transmitters
• Fan Control Output: 3-channel relay contact output for evaporator fan low/medium/high three-speed speed regulation
• Defrost Control Output: 2-channel high-current relay output (electric heating defrost contact, hot gas defrost solenoid valve drive contact)
• Digital Interlock Inputs: 4-channel dry contact input (compressor running feedback, warehouse door interlock, high-low pressure safety switch, defrost termination temperature switch)
• Timing Function Range: Adjustable defrost cycle interval 1–24 hours, adjustable defrost duration 5–90 minutes, post-defrost drip drain delay 1–30 minutes
• Operating Ambient Temperature Range: -30°C ~ +50°C; allowable short-term derated operation up to +60°C
• Altitude Operation Limit: Rated performance within altitude ≤ 1000m; maximum operating altitude 4400m with output current derating
• Relative Humidity Tolerance: Maximum 95% non-condensing relative humidity; supports short-term condensed water splash exposure
• EMC Immunity Compliance: IEC 61000-4-2 ESD 4kV contact / 8kV air discharge; IEC 61000-4-3 RF electromagnetic field 10V/m; IEC 61000-4-4 fast transient burst 2kV power line
• Enclosure Protection Class: IP54 plastic enclosure with internal circuit conformal coating
• Net Weight: 0.35 kg
• Certifications: CE, UL, Eurovent refrigeration equipment standard certification

Material Composition & Structural Features

1. Outer Enclosure: Flame-retardant ABS plastic injection molded sealed enclosure with integrated side wall ventilation micro-slots for internal anti-condensation air circulation
2. Internal Circuit PCB: FR-4 flame retardant circuit board fully coated with transparent polyurethane conformal coating to resist high humidity condensed water and refrigeration oil vapor corrosion
3. Control Electronic Components: Industrial-grade low-temperature resistant microcontroller chip, NTC signal differential amplifier, multi-channel optocoupler isolation chips, high-current miniature power relays, surge suppression varistors
4. Wiring Terminals: Top-mounted pluggable spring terminal blocks for all sensor, power and load wiring; clear printed terminal function identification on enclosure surface
5. Man-Machine Interface: Front panel digital 3-digit display, up/down setting buttons, 8 LED status indicator lamps (fan speed stage, defrost active, compressor interlock, sensor fault, high/low pressure alarm)
6. Mounting Structure: Two integrated mounting lug holes on enclosure side walls for wall-mounted installation inside refrigeration unit electrical control box

Working Principle

1. Two NTC thermistor temperature sensors continuously transmit evaporator coil surface temperature and cold storage room ambient temperature analog resistance signals to the module signal input circuit
2. Internal microcontroller converts thermistor resistance values to accurate temperature readings via built-in temperature-resistance lookup table; calculates coil-ambient temperature difference to indirectly judge frost accumulation thickness on evaporator fins
3. Multi-speed fan control logic adjusts output relay contact combination according to set cold storage temperature target value and real-time temperature deviation; switches evaporator fan between low/medium/high three rotational speed stages to balance cooling capacity and warehouse temperature stability
4. Built-in adjustable timing logic executes automatic periodic defrost cycles at preset time intervals; when defrost cycle activates, the module cuts off all evaporator fan output contacts, closes cold air circulation, and energizes defrost output relay to start electric heating tubes or hot gas defrost solenoid valves
5. Defrost termination temperature sensor signal is continuously monitored during defrost operation; once evaporator coil temperature rises above preset defrost end temperature threshold, the module immediately terminates defrost output and enters post-defrost drip drain delay countdown to allow melted frost water to fully drain before restarting cooling fans
6. Four-channel dry contact interlock input circuit monitors compressor operating state, cold storage warehouse door switch, refrigeration system high/low pressure safety cutout switches; if any interlock safety signal triggers fault state, the module locks fan and defrost output and lights corresponding fault LED indicator
7. Built-in sensor fault diagnosis function continuously detects open-circuit and short-circuit failures of coil and ambient temperature thermistor sensors; sensor circuit fault triggers alarm indicator and switches fan to low-speed safe operating mode to prevent over-freezing or insufficient cooling

Application Scenarios

• Industrial low-temperature cold storage, frozen food warehouse evaporator unit cooler control
• Supermarket commercial refrigerated display cabinets, cold storage back room cooling fan and defrost cycle control
• Food processing factory production line quick-freezing tunnel evaporator automatic defrost and fan speed regulation
• Logistics refrigerated distribution warehouse, fruit and vegetable fresh-keeping constant temperature storage refrigeration unit control
• Marine ship refrigerated cargo hold small evaporator fan and defrost cycle automatic control

Installation Requirements

1. Electrical Box Mounting: Mount the SRB3100 module vertically inside the refrigeration unit dedicated electrical control box via side mounting lugs with M3 plastic insulated bolts
2. Wiring Classification Standard: Separate low-voltage sensor signal wires, 24VAC/DC control power wires and high-current fan/defrost load wires; maintain minimum 10cm wiring spacing between signal cables and high-current load cables to eliminate electromagnetic interference
3. Terminal Wiring Torque Standard: Spring terminal block wire clamping screws tightened to 0.6–0.8 N·m; temperature sensor wiring uses shielded two-core twisted pair cable with single-end shield grounding at module terminal side
4. Internal Anti-Condensation Installation Rule: Do not install the module directly adjacent to evaporator cold coil metal surfaces with low temperature; maintain minimum 15cm air gap between module enclosure and cold metal components to prevent condensed water dripping onto the control module
5. Enclosure Sealing Check: After completing all wiring, fully install the module front panel sealing cover plate and compress the built-in rubber sealing gasket to maintain IP54 dust and water splash protection performance

Operation & Maintenance Precautions

1. Pre-Startup Parameter Setting Rule: Before putting the refrigeration unit into formal operation, adjust three core parameters matching on-site working conditions: defrost cycle interval, defrost operation duration, defrost termination temperature threshold; mismatched parameter values will cause excessive frost accumulation or unnecessary frequent defrost energy waste
2. Condensed Water Inspection Maintenance: Conduct monthly visual inspection of module internal circuit board conformal coating; if condensed water accumulates inside the electrical box and water droplets contact the circuit board, disassemble the module and fully air-dry internal components before restarting operation to avoid short-circuit burnout
3. Thermistor Sensor Calibration Maintenance: Calibrate temperature sensor reading accuracy semi-annually using standard precision temperature calibrator; sensor drift error exceeding ±1.5°C will cause inaccurate frost thickness judgment and abnormal defrost cycle operation
4. High-Current Relay Load Limit: Do not connect defrost electric heating tube load current exceeding the rated contact current of the defrost output relay; overload current will rapidly burn relay contact surfaces and cause defrost cycle failure
5. Low-Temperature Storage Spare Module Maintenance: Store spare SRB31000 modules in room-temperature dry warehouse; avoid long-term storage in cold refrigeration equipment spare parts boxes where temperature fluctuates below 0°C, which will cause internal electrolytic capacitor performance degradation
6. Safety Interlock Fault Handling: If the module lights high/low pressure fault LED indicator, immediately cut off the refrigeration compressor main power supply and inspect refrigeration system pipeline blockage, refrigerant charge volume abnormal or pressure transmitter failure before resetting the module fault state