Yokogawa AFS20D Duplexed Field Control Unit

Suffix Breakdown & Model Matrix

Note: The supplied configuration codes describe selectable hardware and software options. Confirm the complete ordering code against the applicable Yokogawa configuration documentation before selecting a replacement unit.

Hardware Specifications

Vnet and RIO Communication Architecture

The AFS20D provides a dual-redundant Vnet interface for control system communication. Its RIO interface can be configured for single or dual-redundant operation, depending on the selected hardware configuration.

For installations requiring redundant RIO communication, verify the selected bus configuration and the corresponding node interface unit. The /NDF4 and /NDR4 options identify front-mounted and rear-mounted node interface arrangements, respectively, as described in the supplied ordering information.

The dual-redundant communication configuration does not, by itself, establish a specific switchover time or guarantee uninterrupted operation under every fault condition. Refer to the applicable Yokogawa system documentation for redundancy behavior and system-level limitations.

Frequently Asked Questions

Q: How much main memory does the AFS20D provide?

A: The AFS20D provides 16 Mbyte of main memory. The supplied specifications identify battery backup for memory protection during power failure, with a maximum backup duration of 72 hours.

Q: What power supply configurations are available?

A: The listed options are 100-120 V AC, 220-240 V AC, and 24 V DC. The ordering configuration also identifies single or dual AC power system arrangements. Verify the complete unit code before connecting the supply.

Q: How many remote I/O nodes can the AFS20D support?

A: The supplied hardware specifications list a maximum of 8 connectable nodes. Confirm the supported node arrangement and RIO redundancy configuration against the applicable system documentation.

Field Installation Guidelines

• Verify the complete model and suffix code against the cabinet wiring diagram and system configuration documents.
• Confirm the supply voltage and AC or DC power configuration before energizing the unit.
• Check the power terminal connections and protective grounding in accordance with the manufacturer’s installation instructions.
• Verify the Vnet and RIO cable routing against the system network design. Keep communication cables separated from power conductors where required by the installation specifications.
• For redundant RIO configurations, confirm the installed node interface unit, mounting position, and bus connections before commissioning.
• Check the battery condition and memory backup requirements during maintenance. Follow the manufacturer’s prescribed battery replacement and handling procedures.
• Allow sufficient cabinet access and mechanical support for the documented unit weight. Include the additional load from installed nodes when determining cabinet and support requirements.
• Consult Yokogawa System Overview, document GS 33K01A20-50E, for installation conditions and environmental limits not specified in the supplied data.