Hitachi SAMURAI Series Service Manual page 53

2. Control Functions
Control of Master/Slave group
5 Rotation Control
When starting up the modules, the modules with the shortest operation time have priority. (Comparison is carried out
between units with the same priority order settings, though) When stopping modules, the modules with the longest
operation time have priority. If the operation with the minimum number of operating units continues for a long time,
forced rotation control is conducted.
6 Priority order setting
It is possible to set the desired order of priority in operation, when there are machines with different capacities or when
inverter type and continuous control type are mixed together.
(Maximum 8 steps)
In this case, module 1 is operated first, as it has the highest priority, and then a rotation control is performed among
modules 2 to 4, which have the same priority order.
7 Function to cancel the control of Master/Slave group
It is possible to cancel the functions to control the number of units when simultaneous thermo ON/OFF of all the units
is required with without performing the control of Master/Slave group. (Possible in 1-pump systems only)
N O T E
Setting method: In 1-pump system settings, set both waiting time for effect of addition and waiting time for effect of
reduction to "0".

Practical operation
1 At system start-up
First one chiller unit with the highest priority order is started up, and thermo ON/OFF judgement is conducted.
When the conditions to start up the compressor are fulfilled, the rest of modules are started up in sequence.
2 During normal operation
The control of Master/Slave group is not performed.
In case that any module within the same group is set to thermo OFF, the other modules are stopped.
When the conditions for thermo ON are fulfilled, the rest of modules are started up in sequence.
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SMGB0097 rev.0 - 07/2015
Module
HP
Priority order setting