1746-A4 | Allen Bradley | SLC 4 Slots Chassis

Allen Bradley 1746-A4 SLC 4 Slots Chassis

The Allen Bradley 1746-A4, also cataloged as the 1746-A4 chassis module, operates as a dedicated 4‑slot frame for housing SLC 500 PLC and I/O modules within 1746/1747 system architectures.

Hardware Specifications

Backplane Bus Communication Velocity & I/O Density Scaling

The 1746-A4 chassis provides the mechanical and electrical backplane required for SLC 500 module communication. Its 4-slot configuration supports deterministic scan cycles by maintaining stable backplane impedance and ensuring predictable module arbitration. When paired with Allen Bradley processors, the chassis enables scalable I/O density without compromising communication timing. Firmware flash compatibility is determined by the installed CPU, as the chassis itself contains no programmable logic.

Frequently Asked Questions

Q: Can modules be hot-swapped in the 1746-A4 chassis A: SLC 500 modules generally require the chassis to be de‑energized before removal or insertion to avoid backplane faults.

Q: Does the chassis impose current limits on installed modules A: Current limits are defined by the power supply, not the chassis. The 1746-A4 provides only the mechanical and electrical backplane.

Q: Are Series B and Series C modules compatible with this chassis A: Yes. The 1746-A4 supports standard SLC 500 module families across multiple series revisions.

Field Installation Guidelines

• Ensure proper seating of modules to avoid bent backplane pins or intermittent communication.

• Maintain adequate ventilation around the chassis to support module thermal dissipation.

• Route high-voltage wiring separately from low-level signal conductors to reduce noise coupling.

• Verify power supply alignment and secure mounting before energizing the system.

• Keep humidity within 5–95% non-condensing to prevent terminal oxidation.