ABB APBU-44C Branching Unit (64669992H)

General Description

The APBU-44C is a passive termination block designed to simplify wiring between field instruments and the control system I/O modules. It acts as a marshalling point where multi-core cables from the field are terminated and then individually connected to I/O channels via pre-wired cables or jumpers. The unit is typically mounted on DIN rails inside control cabinets and is widely used in ABB's Symphony and Advant systems.

Key Features

• Connection Points: 44 terminals arranged in two rows, accepting wire sizes up to 2.5 mm².

• Fusing Option: Positions for miniature fuses (5x20 mm) on each channel for overcurrent protection (optional).

• LED Indication: Optional LED modules for status indication (e.g., fuse blown).

• Labeling: Transparent covers with insertable labels for clear channel identification.

• Mounting: DIN rail mount (35 mm) according to EN 60715.

• Wiring: Screw terminals with rising cage clamps for secure connections.

• Cross-Connection: Integrated jumpers for common potentials (e.g., 24 V DC common).

Technical Specifications

• Rated Voltage: 250 V AC/DC max.

• Rated Current: 10 A per terminal (with fuse holder 6.3 A max).

• Dielectric Strength: 2.5 kV AC (terminal to rail).

• Operating Temperature: -25°C to +70°C.

• Material: Polyamide 6.6, UL94 V-0 rated.

• Dimensions: 140 x 80 x 55 mm (W x H x D).

• Weight: 0.3 kg.

Functional Description

The APBU-44C serves as a physical interface between field cabling and the control system. Field signals (analog, digital, thermocouple, etc.) are terminated on one side of the unit, while pre-fabricated cables connect to the I/O modules on the other side. The unit may include fuse holders to protect individual field circuits from overcurrent. Jumpers allow commoning of supply voltages or grounds. The design ensures neat cable routing and simplifies troubleshooting, as each channel is clearly marked.

Typical Applications

• Marshalling cabinets in DCS and PLC systems.

• Interface between field junction boxes and control room I/O racks.

• Distribution of 24 V DC power to multiple field devices.

• Termination of thermocouple or RTD wires with cold-junction compensation.

• Breakout of multi-core cables for discrete I/O.

Installation and Wiring

The unit snaps onto a standard DIN rail. Field wires are stripped to 8 mm and inserted into the screw terminals; torque to 0.5 Nm. If fuses are used, they must be ordered separately and inserted after wiring. The transparent cover snaps on to protect terminals and hold labels. For high-vibration environments, additional retaining clips are available. The unit should be mounted in a clean, dry cabinet with appropriate clearance for wiring.

Compatibility

The APBU-44C is designed for use with ABB I/O systems but can be used with any control system requiring organized field termination. It is often paired with pre-wired cables like NKx series to connect directly to S800 I/O modules.

Note: This document covers technical aspects only. For ordering and assembly details, refer to ABB's termination unit documentation.