ABB Advant OCS / AC 450 Series Modules SS823

Technical Dossier

Product Details And Specifications

ABB Advant OCS / AC 450 Series Technical Notes

DriveKNMS maintains a dedicated inventory of Advant OCS and AC 450 series modules — including the SS823 Power Voting Unit — to support facilities that have chosen lifecycle extension over premature system retirement.

The Evolution of Advant OCS / AC 450 Architecture

ABB introduced the Advant OCS platform in the late 1980s as a modular, distributed control architecture built around the Advant Fieldbus (AF 100) and PROFIBUS communication standards. The system was structured around the Master Station (MS) concept, where engineering workstations communicated with field controllers via a proprietary network layer.

The AC 450 controller, introduced in the mid-1990s, represented the primary field controller unit within the Advant OCS framework. It operated on a rack-based backplane architecture, accepting a range of I/O modules, communication adapters, and power supply units through a standardized slot interface. This design allowed incremental expansion without full system replacement — a characteristic that made the platform commercially durable well beyond its original design life.

By the early 2000s, ABB began transitioning its DCS portfolio toward the AC 800M (System 800xA) platform. The Advant OCS and AC 450 lines were formally discontinued, though ABB continued to provide limited support for installed bases. As of 2026, the platform is in full end-of-life status: no new modules are manufactured, factory support has ceased, and spare parts availability depends entirely on secondary market channels and specialist distributors.

The architectural transition from Advant OCS to AC 800M introduced incompatibilities at the backplane, firmware, and communication protocol levels. Direct module substitution between generations is not possible without engineering intervention. This incompatibility is the primary driver of demand for original Advant OCS and AC 450 spare parts in the secondary market.

Advant OCS / AC 450 Full Catalog & Functionalities (SKU List)

The following modules represent the verified core of the Advant OCS and AC 450 spare parts catalog, organized by functional category.

Power Supply & Power Management

• SS823: Power Voting Unit — manages redundant power supply arbitration within the AC 450 rack, ensuring uninterrupted controller operation during single PSU failure.
• SS822: Power Supply Unit — primary 24 VDC rack power supply for AC 450 controller stations.
• SS821: Power Supply Module — secondary/redundant power supply, paired with SS822 in high-availability configurations.

Central Processing Units (CPU)

• PM645B: AC 450 Processor Module — primary CPU for the AC 450 controller, executes control application and manages I/O bus communication.
• PM646: AC 450 Processor Module (enhanced) — higher-memory variant of the PM645B, used in applications with large control databases.
• PM150: Advant Controller 160 Processor — CPU module for the smaller AC 160 sub-platform within the Advant family.
• PM511V16: AC 500 Processor Module — CPU used in the AC 500 sub-range, compatible with select Advant I/O expansion racks.

Analog Input (AI) Modules

• AI810: 8-channel analog input, 4–20 mA / 0–10 V, HART-capable — the most widely deployed AI module in the Advant OCS installed base.
• AI820: 8-channel analog input with galvanic isolation — used in applications requiring channel-to-channel isolation in hazardous environments.
• AI830: 8-channel thermocouple/RTD input — temperature measurement module for process applications.
• AI835: 8-channel RTD input, PT100 — dedicated resistance temperature detector input module.

Analog Output (AO) Modules

• AO810: 8-channel analog output, 4–20 mA — standard current loop output module for control valve and actuator interfaces.
• AO820: 8-channel analog output with HART — output module with HART pass-through for smart field device communication.

Digital Input (DI) Modules

• DI810: 16-channel digital input, 24 VDC — standard discrete input module for pushbutton, limit switch, and relay contact interfaces.
• DI820: 16-channel digital input, 120 VAC — AC voltage digital input for legacy field wiring at higher voltage levels.
• DI830: 16-channel digital input with diagnostics — enhanced DI module with per-channel open-wire detection.

Digital Output (DO) Modules

• DO810: 16-channel digital output, 24 VDC — standard discrete output for solenoid valves, motor starters, and relay coils.
• DO820: 16-channel relay output — dry contact relay output module for high-voltage switching applications.

Communication & Fieldbus Adapters

• CI854: PROFIBUS DP communication interface — connects the AC 450 controller to PROFIBUS DP field device networks.
• CI856: AF 100 Advant Fieldbus interface — native Advant Fieldbus communication adapter for inter-controller and I/O station communication.
• CI858: DriveBus communication interface — dedicated adapter for ABB drive network integration within Advant OCS.
• CI860: FOUNDATION Fieldbus HSE interface — high-speed Ethernet fieldbus adapter for FF-H1 segment integration.

Sourcing Hard-to-Find & Obsolete Advant OCS / AC 450 Parts

The Advant OCS and AC 450 platform reached end-of-manufacturing status over a decade ago. ABB's authorized service network no longer stocks new modules, and factory repair services for this generation have been discontinued. Facilities that experience module failure face a binary choice: source a replacement from the secondary market, or initiate a full system migration.

For procurement teams managing multi-site Advant OCS installations, DriveKNMS offers long-term supply agreements and bulk reservation of critical spare modules. Establishing a strategic spare parts buffer — typically 2–3 units of each critical module type — is the most cost-effective method of extending system operational life by 5–10 years without capital expenditure on platform migration.

Quality Control for the Advant OCS / AC 450 Range

Legacy DCS modules present specific failure modes that differ from modern hardware. Our QA process for Advant OCS and AC 450 modules addresses the known degradation patterns of this hardware generation: