Description

ABB DO821 Digital Output Relay Module

The ABB 3BSE013250R1 DO821, also cataloged as the DO821 Digital Output Relay Module, provides 230 V AC/DC relay switching execution within the ABB S800 I/O system. The module contains 8 individually isolated NC relay output channels with field voltage supervision and ModuleBus diagnostics.

Hardware Specifications

Parameter	Specification
Model	DO821
Brand	ABB
Article Number	3BSE013250R1
Product Type	Digital Output Relay Module
System Platform	ABB S800 I/O
Signal Type	Relay (NC)
Signal Specification	230 V AC/DC, 5-250 V AC/DC, 3 A
Number of Channels	8
HART Support	No
SOE Support	No
Redundancy	No
High Integrity	No
Intrinsic Safety	No
Isolation	Individually isolated channel-to-channel and to circuit common
Maximum Output Voltage	250 V AC
Maximum Continuous Output Current	3 A
Current Limiting	Supported through MTU
Maximum Field Cable Length	600 m
Rated Insulation Voltage	250 V
Dielectric Test Voltage	2000 V AC
Power Dissipation	Typical 2.9 W
Current Consumption +5 V ModuleBus	60 mA
Current Consumption +24 V ModuleBus	140 mA
Current Consumption +24 V External	0
Operating Temp	0 to +55 deg C
Storage Temp	-40 to +70 deg C
Relative Humidity	5 to 95 %, non-condensing
Protection Class	IP20 according to IEC 60529
Weight	0.23 kg
Dimensions	45 mm W x 119 mm H x 102 mm D, 111 mm D including connector
Compatible MTU	TU811, TU813, TU831, TU836, TU837, TU851
Keying Code	CA

ABB S800 ModuleBus Relay Output Diagnostics

The DO821 uses optical isolation barriers, relay drivers, output status LEDs, relay contacts, and EMC protection components for each output channel. Additionally, the module monitors the relay supply voltage derived from the 24 V ModuleBus distribution.

The relay power converter supervision generates a module error signal when the supply voltage disappears. Furthermore, the Warning LED indicates the abnormal condition, and the diagnostic information remains available through the ModuleBus communication interface. The supervision function can be enabled or disabled through configuration parameters.

The S800 I/O architecture supports high I/O density scaling through standardized ModuleBus communication. Therefore, the DO821 integrates directly into ABB distributed control environments where deterministic I/O update behavior and channel-level isolation are required.

Frequently Asked Questions

Q: Does the DO821 support redundant output operation?
A: No. The DO821 is a non-redundant digital output module with 8 individually isolated NC relay channels.

Q: How does the module detect relay supply failures?
A: The module monitors the 24 V ModuleBus-derived relay supply voltage and reports faults through ModuleBus diagnostics when the voltage disappears.

Q: Can the DO821 outputs be connected to mixed AC and DC field loads?
A: The module supports 5-250 V AC/DC relay switching signals within the specified output voltage and current limits.

Field Installation Guidelines

Install the DO821 on approved ABB S800 I/O mounting components with the specified compatible MTU. Verify the keying code before module insertion to prevent incorrect hardware installation.

Route field wiring separately from high-voltage power cables and maintain proper cable segregation according to industrial control cabinet practices. Connect protective earth and shielding according to the cabinet grounding design.

Before commissioning, check relay output wiring, channel status LEDs, ModuleBus communication status, and relay supply supervision parameters. Confirm that connected field devices remain within the rated voltage and current limits.

Specifications

• Brand: ABB

Advantages

• High reliability in industrial environments
• Supports continuous operation
• Compatible with major PLC/DCS systems