1791-16BC 16/16 DC Block I/O Module Allen-Bradley

1791-16BC Allen‑Bradley 16/16 DC Block I/O Module

Product Introduction

The 1791-16BC from Allen‑Bradley is a discrete block I/O module. It features sixteen (16) input channels and sixteen (16) output channels. Both inputs and outputs accept 10‑30VDC signals. This module comes with an embedded power supply, a PLC communication interface, and signal conditioning circuitry. Therefore, it functions as a complete remote I/O chassis in a single compact housing. You can use the 1791-16BC to implement remote I/O architecture across your facility.

Technical Specifications

The 1791-16BC delivers balanced I/O capacity. Below are the key electrical and functional details:

• Inputs per block: 16

• Outputs per block: 16

• Number of groups: 2 groups of 8

• Input on‑state voltage range: 10‑30VDC

• Input on‑state current: 11mA @ 30V max.

• Input off‑state voltage: 5VDC max.

• Input off‑state current: 1.5mA min.

• Output voltage range: 10‑30VDC

• External power voltage: 19.2‑30VDC

• External power current: 300 mA

• Maximum power dissipation: 17.8 Watts

• Maximum thermal dissipation: 60.6 BTU/Hr

• Mounting options: Vertical or horizontal

Additionally, the 1791-16BC requires an external power supply of 19.2‑30VDC at 300 mA for its internal logic. The module converts this power to drive its outputs and process input signals.

Remote I/O Compatibility and Baud Rates

The 1791-16BC works as a Remote I/O (RIO) adapter. It always functions in adapter mode. Therefore, you need a RIO scanner in your controller to exchange data. This module is compatible with several Allen‑Bradley platforms, including PLC‑2, PLC‑3, PLC‑5, and the SLC 500 product family.

The supported RIO baud rates depend on your controller. Meanwhile, the maximum cable length changes with each baud rate:

• At 57.6K baud: maximum 10,000 cable‑feet

• At 115.2K baud: maximum 5,000 cable‑feet

• At 230.4K baud: maximum 2,500 cable‑feet

For instance, if you place the 1791-16BC far from the main controller, use a lower baud rate to maintain signal integrity.

Mounting, Wiring, and Installation

You can mount the 1791-16BC either vertically or horizontally. Each orientation has a different output current rating due to heat dissipation differences. Specifically:

• Vertical mounting at 60°C: 500 mA per output

• Horizontal mounting at 60°C: 250 mA per output

Lower temperatures allow higher currents. For example, at 30°C, vertical mounting supports 1 Amp per output. Horizontal mounting at 30°C supports 500 mA per output. Furthermore, the maximum surge current for the 1791-16BC is 3 Amps for 50 milliseconds.

Connect this module in a daisy‑chain topology. The 1791-16BC must be installed inside an enclosure. This protects it from dust, dirt, grease, oil, water, and chemicals. The enclosure must meet the requirements of your installation area’s classification. Also, maintain a clearance of 2 inches on all sides of the module for proper airflow.

Internal Protection and Physical Dimensions

The 1791-16BC has an internal fuse. Therefore, no external power fusing is required for the module’s internal logic. However, note that the output channels are not fused. We recommend adding external fuses on each output channel for protection against overcurrent conditions.

Physical dimensions of the 1791-16BC are:

• Height: 6.95 inches

• Width: 4.35 inches

• Depth: 3.85 inches

The device weighs 1.02 kg (2.25 lbs). Its compact size allows placement near field devices or strategically across the plant floor.

Packaging List

• 1791-16BC module (1 unit)

• Built‑in terminal strip (pre‑attached)

• Captive screws (2 pcs)

• Quick start installation guide

Note: No certificates or warranty documents are included in the package.

Shipping Information

We ship using FedEx, UPS, or DHL. The gross weight is 1.02 kg. Each unit is packed in anti‑static and anti‑shock materials. Delivery typically takes 5–7 business days depending on your location.

Frequently Asked Questions (FAQ)

1. Which controllers work with the 1791-16BC?
The 1791-16BC is compatible with Allen‑Bradley PLC‑2, PLC‑3, PLC‑5, and SLC 500 series controllers. It requires a RIO scanner on the controller side.

2. Do I need an external power supply for the outputs?
Yes. The 1791-16BC needs an external DC power supply of 19.2‑30VDC at 300 mA for its logic. The outputs share this power, so size the supply according to your total load.

3. Can I mount the 1791-16BC vertically?
Absolutely. Vertical mounting is supported and actually provides a higher output current rating (500 mA at 60°C) compared to horizontal mounting (250 mA at 60°C).

4. Are the output channels fused internally?
No. Only the module’s internal logic is fused. The sixteen output channels on the 1791-16BC are not fused. We recommend adding external fuses for each output.

5. What is the maximum cable length for remote I/O with this module?
It depends on the baud rate. For the 1791-16BC, use 10,000 feet at 57.6K baud, 5,000 feet at 115.2K baud, or 2,500 feet at 230.4K baud.