Allen-Bradley 1769-PB4 CompactLogix DC Power Supply 4 A

A 24V DC powered supply for Compact I/O banks

The Allen-Bradley 1769-PB4 is the DC-input power supply of the 1769 Compact I/O and CompactLogix family. It takes a 24V DC supply (19.2 to 31.2V DC) from a control panel source and produces the 5V DC backplane supply and a 24V DC field bus for the controller and I/O modules, with 4.0 A at 5V DC and 1.7 A at 24V DC.

It suits panels that have no AC mains, such as skids and remote stations running from a DC battery or a 24V DC supply, where it avoids an extra AC step. The 1769-PB2 is the smaller DC type, with 2.0 A at 5V DC and 0.7 A at 24V DC.

Technical specifications

Capacity and power budget

The 4 A supply is listed for 100VA input consumption at 24V DC, with 14.5 W dissipation at 60 °C and an inrush current of up to 30 A at 31.2V DC. Size the upstream 24V DC supply and its protection for that inrush, not only for the running current.

Add the 5V DC and 24V DC draws of all the modules, then compare them with 4.0 A and 1.7 A. A bank can have up to eight I/O modules on each side of the supply, 16 in total, but individual module distance ratings may reduce that figure; for example the 32-point output module is rated for six modules.

Mounting and wiring

Mount the supply on a DIN rail or panel with M4 or #8 screws at 1.16 N.m. The unit is 118 x 70 x 87 mm and weighs 630 g. Wire with 14 AWG (2.5 mm²) solid copper rated 90 °C or greater. Isolation is 75V continuous, reinforced insulation type, and IEC Class 1 grounding is required.

Operating temperature is 0 to 60 °C, the enclosure rating is open-style, and the sheet provides derating and dissipation curves for the 4 A supplies. A fuse of 6.3 A is listed for the 4 A models. The DC supply must be Class 2 or otherwise suitable according to the local requirements.

Documents and quotation

The power-supply technical data 1769-TD008 contains the full table. Send the 1769-PB4 reference, series, quantity and the bank module list for a quotation. Related items are listed in PLC & I/O Cards.

How the 1769-PB4 Works

The 1769-PB4 is a switch-mode supply that converts a 24V DC panel source into the two rails carried on the Compact I/O bus: 5V DC for module logic and communication, and 24V DC for modules that need it, such as many analog modules. The supply sits inside the bank and feeds modules on both its left and right sides through the bus connectors that join adjacent modules, so there is no separate power wiring to each I/O module.

Because every Compact I/O bank that is not attached to a MicroLogix 1500 base needs its own power supply, the 1769-PB4 is also used to power additional banks connected through expansion cables. A DC-input supply is the natural choice where the panel already has a regulated 24V DC bus, a battery-backed DC system or a solar-charged supply, since no AC source is required.

1769-PB4 Selection & Ordering Guide

• AC or DC input: the 1769-PA2 and 1769-PA4 accept AC mains, the 1769-PB2 and 1769-PB4 accept 24V DC. Choose the PB versions only where a suitable DC source is available.
• 2 A or 4 A: add the 5V DC and 24V DC current draw of every module in the bank, then compare the totals with the 4.0 A and 1.7 A capacity of the 1769-PB4. If the bank is close to the limit, keep a margin or split the I/O into two banks.
• Distance rating: check the power-supply distance rating of each module (for example 6 modules for the 1769-OB32 and 8 for most analog modules) when deciding where the supply sits in the bank.
• Coated version: the 1769-PB4K is the conformal-coated variant for harsher atmospheres.
• Accessories: each bank ends with a right or left end cap terminator, and banks are linked with 1769 expansion cables; confirm these when ordering a complete system.

To request a quote for the 1769-PB4, send the module list of the bank and the available supply voltage. Our team can help confirm the correct ordering code.

Installation & Maintenance

Install the supply on the DIN rail or panel with the I/O modules, leaving the ventilation clearance shown in the installation instructions, and keep it within the 0 to 60 °C operating range. Protect the incoming 24V DC circuit with a breaker or fuse sized for the inrush current as well as the running current, and use a source that meets the Class 2 or local electrical requirements stated by Rockwell Automation. Ground the unit as the instructions specify.

The installation instructions include a fuse replacement procedure; replace the fuse only with the type Rockwell Automation specifies, and investigate the cause of a blown fuse before re-energising. During maintenance, measure the input voltage under load, check terminal tightness and look for discoloration around terminals, which can indicate a loose connection. Power must be removed before modules are added or removed from the bank.

Typical Applications in Oman & the GCC

• Remote telemetry and RTU panels on pipelines and water networks powered from battery-backed 24V DC systems.
• Solar-powered monitoring stations where no AC supply is available.
• Packaged skids for compressors, pumps and chemical injection with a 24V DC control bus.
• Machine panels in manufacturing and food plants that standardise on 24V DC control.

Why Source the 1769-PB4 from Seven Star LLC

Seven Star LLC supplies Allen-Bradley CompactLogix and Compact I/O components, including the 1769-PB4 power supply, across Oman and the GCC. Request a quote with the catalog number and quantity, and our team can help confirm the correct ordering code and the end caps or cables your bank needs.