4256A84G03 / 3A99159G03 Emerson Ovation WDPF DCS 3rd-Gen High Reliability Isolated Relay Output Module
4256A84G03 is the original Westinghouse drawing part number, while 3A99159G03 is Emerson’s official standardized aftermarket spare part number. These two part numbers refer to the exact same third-generation high-reliability isolated relay output module, fully plug-and-play backward compatible with earlier versions 4256A84G01 and 4256A84G02. It works in tandem with 4256A25 series MRC main remote control boards and 4256A26 remote expansion boards for Ovation remote I/O rack installation; no adjustments to system logic programs, parameters or configurations are required during card replacement.
Description
This module converts digital control commands transmitted from the MRC master controller into mechanical contact switching signals via fully isolated hermetically sealed industrial relays. It is used to drive field solenoid valves, alarm horns, panel indicator lights, small auxiliary contactors, safety interlock loops and low-power on-site actuators. Every channel adopts a dual-stage isolation design: optocoupler front-end isolation plus relay rear-end isolation, which completely eliminates cross-channel signal crosstalk, ground loop coupling noise and external electromagnetic interference. Built-in full-coverage intelligent fault diagnosis logic can detect relay contact adhesion, output circuit open-circuit, short-circuit overload and abnormal back EMF from inductive loads, and upload real-time single-channel fault alarms to the DCS host through the MRC Link differential bus.
Compared with the G01 and G02 legacy revisions, the G03 version upgrades long-life sealed industrial relays with superior mechanical and electrical switching endurance. It is equipped with three-stage composite surge absorption circuits and high-efficiency freewheeling protection circuits for coil-based inductive loads. The multi-layer EMI-suppression PCB layout is optimized to adapt to heavy industrial sites with intense electromagnetic radiation. A full-cycle relay contact health monitoring function is added, and the response speed for fault state feedback is improved, making it perfectly suited for high-frequency switching and high-safety interlock control scenarios in thermal power, petrochemical and metallurgical industries.
The circuit board uses multi-layer high-temperature resistant FR-4 industrial PCB with a 360° fully enclosed electromagnetic shielding structure. Each independent relay output channel provides 1000V AC/DC reinforced galvanic isolation between field wiring terminals and internal logic circuits, effectively blocking lightning surge impacts, high-frequency radiation and back EMF interference generated by high-voltage switchgears, large rotating machinery and frequency converters. All finished products pass full-lifecycle strict factory reliability verification, including a 72-hour high-low temperature cyclic aging test, full-channel relay pull-in/release precision calibration, long-duration full-load MRC Link bus continuous burn-in test, and comprehensive simulation tests of relay contact wear, wiring open-circuit and short-circuit faults.
The module supports single-slot hot-swappable online replacement without powering off the entire remote I/O station. Each output channel integrates multi-layer comprehensive hardware protection functions: surge suppression, instantaneous overcurrent cutoff, reverse polarity prevention, inductive load back EMF absorption and overload self-locking protection, which avoids permanent module damage caused by on-site wiring misoperation or load short-circuit failures. Independent LED diagnostic indicators separately display power supply status, MRC bus communication link status, real-time relay on/off output status and single-channel loop fault alarm information, enabling rapid on-site inspection and troubleshooting.
Technical Specifications
PCB Substrate: Multi-layer high heat-resistant FR-4 industrial printed circuit board
Operating Temperature Range: -25℃ ~ +75℃
Storage Humidity: 5% ~ 90% RH, non-condensing
EMC Compliance: Industrial Class II, CE certified, compliant with EN 61000 series anti-interference standards
Communication Bus: Dedicated MRC Link differential bus for Ovation remote I/O racks
Channel Isolation Withstand Voltage: 1000V AC/DC galvanic isolation per independent relay output channel
Output Type: Sealed industrial mechanical isolated relay contact output, compatible with AC/DC low-load on-site interlock equipment driving
On-board Integrated Protections: Surge suppression, overcurrent protection, reverse polarity prevention, inductive load freewheeling protection, overload self-locking lockout
Installation Mode: Single-slot hot-swappable plug-in module matching standard Ovation DCS rack backplane
Quality Warranty: Genuine original Emerson/Westinghouse product, supplied with independent factory inspection test report, 12-month official warranty
Application Fields
Medium and large thermal power plant Ovation WDPF distributed control systems; interlock control cabinets for process regulating valves in petrochemical plants; logic drive stations for auxiliary equipment of metallurgical smelting furnaces; flue gas baffle and safety alarm control systems of municipal waste incineration plants; auxiliary actuator control racks for pulp & paper production lines; multi-rack redundant central control rooms of traditional heavy industry; high-safety interlock and auxiliary equipment logic automation platforms for energy and chemical continuous production lines; centralized DCS monitoring and control systems for large-scale distributed energy storage power stations
Get a Quote