Description

The MODICON NW-BM85C002 is a legacy but still widely deployed BM85 Bridge Multiplexer module developed by Schneider Electric (under the Modicon brand) to enable seamless communication between Modbus Plus (MB+) networks and serial Modbus RTU/ASCII devices. Designed primarily for use with Modicon Quantum PLC systems, the NW-BM85C002 acts as a protocol gateway—allowing up to 32 remote serial devices (such as energy meters, VFDs, temperature controllers, or I/O concentrators) to be integrated into a high-speed Modbus Plus backbone.

Housed in a rugged metal enclosure suitable for DIN-rail mounting, the MODICON NW-BM85C002 features dual configurable serial ports (RS-232 and RS-485), each capable of independent baud rates and device addressing. This flexibility makes it invaluable in brownfield automation projects where modern PLCs must coexist with older instrumentation that only supports serial Modbus. The unit operates autonomously—requiring no external configuration software once set via DIP switches—and includes status LEDs for power, network activity, and port communication health.

Despite being part of an older product line, the MODICON NW-BM85C002 remains critical in industries like water/wastewater, power generation, and manufacturing, where system lifecycles exceed 20 years and full migration to Ethernet-based protocols is cost-prohibitive.

MODICON NW-BM85C002

Technical Specifications

Main Features and Advantages

Legacy-to-modern integration without system overhaul: The MODICON NW-BM85C002 allows plant engineers to retain valuable field instruments while upgrading central control to a Quantum PLC platform. Instead of replacing hundreds of Modbus RTU sensors or drives, users simply connect them through the NW-BM85C002, which presents them as native nodes on the Modbus Plus network—enabling centralized polling and diagnostics from the PLC logic.

Plug-and-play operation with robust industrial design: Once configured via hardware switches (eliminating dependency on aging configuration software), the MODICON NW-BM85C002 runs autonomously with no firmware updates or maintenance. Its metal housing and conformal-coated PCB provide resilience against dust, humidity, and electrical noise common in pump stations or boiler rooms.

Proven reliability in mission-critical infrastructure: With decades of field deployment, the MODICON NW-BM85C002 has demonstrated exceptional uptime in applications where communication failure could lead to process shutdowns or safety hazards. Its deterministic polling mechanism ensures predictable response times, critical for closed-loop control involving flow meters or pressure transmitters.

Application Field

In municipal water treatment facilities, the MODICON NW-BM85C002 aggregates data from chlorine analyzers, ultrasonic level sensors, and chemical dosing pumps—all communicating via Modbus RTU—into the central Quantum PLC’s Modbus Plus network. This enables operators to monitor and adjust treatment parameters from a single HMI without installing additional gateways.

Within combined-cycle power plants, the MODICON NW-BM85C002 interfaces legacy turbine governors and excitation controllers (which only support RS-485 Modbus) with the main DCS built on Modicon Quantum. This avoids costly turbine control system replacements while maintaining compliance with grid telemetry requirements.

For food & beverage production lines, the MODICON NW-BM85C002 connects pasteurizers, fillers, and labelers—each with embedded Modbus RTU controllers—to the plant-wide Modbus Plus backbone. Maintenance teams benefit from unified fault reporting, reducing troubleshooting time during changeovers or sanitation cycles.

In mining conveyor systems, the MODICON NW-BM85C002 links belt scale integrators, pull-cord switches, and motor protection relays to the central control room, enabling coordinated stop/start sequences and overload alerts across kilometers of transport infrastructure.

MODICON NW-BM85C002

Related Products

NW-BM85C001: Older variant with slightly different port labeling; functionally similar
AS-BMKC-200: Replacement BM85 bridge with enhanced diagnostics (discontinued but compatible)
140CPU67160: Modicon Quantum CPU often used with NW-BM85C002 in large I/O systems
MB+ Network Tap (990NAD23000): Diagnostic tool for monitoring Modbus Plus traffic to/from NW-BM85C002
Modbus Plus Drop Cable (990NAD21810): Shielded twisted-pair cable required for MB+ connection
Quantum I/O Modules (e.g., 140CRP93100): Complementary modules in full Quantum rack deployments

Installation and Maintenance

Pre-installation preparation: Before installing the MODICON NW-BM85C002, verify the Modbus Plus network’s token rotation time and ensure sufficient bandwidth for the planned number of remote devices. Set the unit’s node address (1–64) using the rotary switch and configure baud rate/data format via DIP switches per your field devices’ specs. Use shielded cables for RS-485 runs, with terminators at both ends if distance exceeds 50 meters. Ground the DIN rail and enclosure properly to minimize EMI.

Maintenance recommendations: Although solid-state with no moving parts, the MODICON NW-BM85C002 should be inspected annually for corrosion on terminals or loose connectors—especially in coastal or chemical environments. Monitor the “COMM” LED; steady blinking indicates normal polling, while off or solid-on suggests configuration mismatch or cabling fault. Keep spare units in climate-controlled storage (10–30°C,<60>