1769-PB4 Allen-Bradley CompactLogix 24VDC Power Supply Module

Product Overview

The Allen-Bradley / Rockwell Automation 1769-PB4 is an expansion DC power supply module engineered for CompactLogix and 1769 Compact I/O assembly banks. Operating on an input voltage range of 19.2 to 31.2 V DC (24 V DC nominal), it distributes backplane power to adjacent I/O modules, delivering up to 4.0 A at 5 V DC and 2.0 A at 24 V DC. It supports mounting up to 8 I/O modules on either side of the power supply casing for a maximum bank capacity of 16 modules.

Technical Specifications

System Architecture and Power Distribution Limits

The 1769-PB4 supplies secondary bus power when a primary controller's power budget is exceeded. Control engineers position the module between expansion banks, extending the local 1769 bus up to 8 slots left and 8 slots right. System total current draw across all attached modules must not exceed the 4.0 A (5 V DC) or 2.0 A (24 V DC) internal output thresholds.

Installation, Grounding, and Wiring Guidelines

Mount the unit onto a standard 35 mm DIN rail or directly to a panel subplate using screws (handling 20G operational shock on DIN rail, 30G on panel). Terminate input 24 V DC wiring using 14 AWG (2.5 mm²) 90 °C copper wire. To ensure safe surge dissipation and regulatory compliance, connect an IEC Class 1 protective earth wire directly to the terminal block ground screw.

Diagnostic Capabilities and Operational Status

A green PWR status LED on the front faceplate verifies that input voltage is present and internal regulation circuits are operational. If the PWR LED fails to illuminate while 24 V DC input is measured across field terminals, the internal slow-blow protection fuse (6.3 A rating) must be checked for continuity before replacing the module.

Target Equipment and Application Scenarios

• Expanding 1769 Compact I/O banks in 24V DC battery-backed remote telemetry units (RTUs).
• Providing isolated bus power in mobile industrial equipment and solar-powered control skids.
• Supplementing backplane power in high-density digital and analog I/O control enclosures.
• Powering distributed CompactLogix racks installed in process plants without AC mains infrastructure.

Global PLC Spare HUB's Insight

When engineering 24V DC distribution for the 1769-PB4, beware of initial power-up peak demand. The unit exhibits an inrush current spike up to 30 A at 31.2 V DC. If an undersized power supply or overly sensitive DC circuit breaker feeds this module, the inrush transient can trip primary protection during startup. Always size upstream 24V power supplies with adequate peak load overhead. If the module output fails suddenly following a field short circuit, inspect internal fuse model Wickmann 19193-6.3A or Littelfuse 021706.3MXP before condemning the power supply circuitry.

Selection and Purchasing Guide

Select the 1769-PB4 when your cabinet utilities run on standard 24 V DC power. If your system relies on 120/240 V AC supply lines, choose the 1769-PA4 AC power supply model instead. Calculate the total backplane current draw of all planned expansion modules using Studio 5000 hardware selection tools to confirm the total load remains under 4.0 A at 5 V DC and 2.0 A at 24 V DC.

Certifications, Package Contents, and 12-Month Warranty

Each unit ships in original factory packaging accompanied by installation literature and terminal protective covers. All modules are backed by a comprehensive 12-month replacement warranty covering technical defects and operational reliability.

Shipping and Express Delivery Terms

Orders process immediately and dispatch within 24 to 48 hours following payment confirmation. Priority global air freight is provided via FedEx, UPS, or DHL. Automated email notifications provide tracking numbers immediately upon carrier dispatch.

Frequently Asked Questions (FAQ)

Q: How many total I/O modules can a single 1769-PB4 power supply support?

A: It can support up to 16 modules total (maximum 8 modules installed to the left and 8 modules to the right), provided the combined backplane current draw remains within rated limits.

Q: What causes the front PWR LED to stay off when 24 V DC power is verified at the terminals?

A: An internal blown fuse (6.3 A rating) caused by an external overvoltage spike or backplane short circuit will prevent the LED from lighting and halt power output.

Q: What is the primary operational difference between the 1769-PB4 and 1769-PA4 power supplies?

A: The 1769-PB4 requires a 19.2 to 31.2 V DC input supply, whereas the 1769-PA4 operates on 85 to 265 V AC incoming power.

Q: Is protective grounding mandatory when installing this DC power supply?

A: Yes, IEC Class 1 grounding is strictly required to satisfy continuous 75 V continuous isolation ratings and protect internal electronics from static discharges.

Q: How can engineers prevent upstream 24V power supplies from tripping during system startup?

A: Select a bulk 24V supply capable of handling short 30 A peak inrush transients and use power distribution circuit breakers with C-curve or slow-trip characteristics.

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