Sequencing; Multisab Sequencing; Sequencing Parameters - Johnson Controls SABROE UniSAB III Engineering Manual

8: Multisab Master
Start#
Compr#
If selecting Compr#, the compressor with the lowest compressor number will always be the regulator in
a Multisab system independent of the starting sequence. If selecting Start#, the compressor with the
lowest starting number and which is in Remote/Multisab will be the regulator.
6.2

Sequencing

6.2.1

Multisab sequencing

Multisab is a distributed compressor control system which is very useful when more compressors are
working together (e.g. connection to the same suction line). With Multisab it is possible to start, stop and
capacity regulate compressors according to the varying cooling requirements.
Multisab is a standard function in UniSAB III. The system is described in detail in the UniSAB III se-
quence manual. In order for Multisab to work, all UniSAB III units which should participate in the distrib-
uted control must be physically connected via the Danbuss communication network. Fig. 45 in
subsection 8.5.3 Configuration of RS485 port/Danbuss describes how to connect the units.
To get optimal use out of Multisab it is very important that certain key parameters are selected correctly
by the user as explained in subsection Multisab regulation. To explain the contents of the Sequencing
picture, the following key parameters are described here: Compr. no, Start no, System no, System regu-
lator, Multisab Master, Compr. Mode, Compr. Status, Multisab Status and Control Mode.
6.2.2

Sequencing parameters

Always make sure that all UniSAB III units on a network have different compressor numbers, i. e. two
units are not allowed to have the same Compr. no. See subsection 6.4.4 Plant.
System no tells Multisab which compressors are going to work together.
Fig. 23 below shows two examples.
UNISAB
Compr. 1
Suction line, sub-plant 1
UNISAB
System no. = 1
Compr. 2
Common
Multisab
network
UNISAB
Compr. 3
Suction line, sub-plant 2
UNISAB
System no. = 2
Compr. 4
Separated compressor plants
Fig. 23: Examples of compressor systems
In the left example two separate compressor plants are connected on a common Danbuss network. In
this system it is very important that:
System no.
UNISAB
= 1 or 2
Compr. 1
System no.
UNISAB
= 1 or 2
Compr. 2
Multisab
network
System no
= 1 or 2
UNISAB
Compr. 3
System no.
UNISAB
= 1 or 2
Compr. 4
Common compressor plant
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Suction main line 1
System no. = 1
Suction main line 2
System no. = 2
Engineering manual - UniSAB III 1.10.8
001930 en 2021.06
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