General setup rules

An ABB AC 31 system always includes an AC 31 central unit. There are three types of central units:

– The 40 series central unit, with a local inputs / outputs extensions interface

– The 50 series central unit, with a local inputs / outputs extensions interface

and a CS 31 bus interface

– The 90 series central unit, with a CS 31 bus interface

Each central unit incorporates a specific number of binary inputs / outputs and occasionally

analog. It is possible, depending on the central unit, to increase the number of inputs / outputs,

to add input / output extensions connected directly to the central units or remote input / output

units via the CS 31 twisted pair.

Central units with extensions

The 40 and 50 series. It’s possible to increase the number of inputs / outputs of the basic

central unit by adding up to 6 local extension units of either type, binary or analog (Figure 1-1).

2.2. Central units with CS 31 bus

The 50 and 90 series. It’s possible to increase the number of inputs / outputs of the basic

central unit by adding remote units. The central unit controlling the system is called the

MASTER central unit. The maximum bus length is 500 m without an amplifier and 2000 m with

3 amplifiers (1 NCB or NCBR unit enables bus amplification for 500 m).