ABB DO821 3BSE013250R1 Isolated NC Relay Module

Product Overview

The ABB DO821 is a specialized 8-channel relay output module designed for the S800 I/O system. Unlike standard "Normally Open" (NO) modules, the DO821 features Normally Closed (NC) contacts. This makes it an essential component for safety-interlocking or fail-safe circuits where a signal must remain closed during normal operation or in the event of a logic power loss. With individual galvanic isolation for every channel, it safely manages a broad range of voltages from 24V to 230V AC or DC.

Core Performance Features

• Normally Closed (NC) Logic: The contacts remain closed when the module is unpowered or the output is "Off," providing a hardware-level fail-safe for critical control loops.

• Total Channel Independence: Every channel is individually isolated, allowing you to switch different voltage phases or independent power sources (AC and DC) within a single module.

• High Switching Capacity: Capable of handling 3A per channel for AC loads (with $\cos \phi > 0.4$) and up to 42W for DC applications.

• Universal Voltage Range: Operates across a wide spectrum from 24V to 230V AC/DC, eliminating the need for external interposing relays in many high-voltage scenarios.

• Industrial Durability: Engineered to withstand harsh environments, the module fits a slim 45mm profile to maximize DIN rail density.

Technical Breakdown

• Part Number: 3BSE013250R1

• Designation: DO821

• Output Type: Relay (Normally Closed)

• Channel Count: 8 (Individually Isolated)

• Max Current: 3A (AC) / 42W (DC)

• Operating Voltage: 24–230V AC/DC

• Dimensions: 119mm (H) x 45mm (W) x 102mm (D)

• Net Weight: 0.3 kg