Lennox CLIMATIC 60, User Manual

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CLIMATIC™ 60 – AIRCOOLED CHILLERS
MUL 41E -0610/ 06-2011 Page 35
21 - MASTER / SLAVE
21.1 - Function
The CLIMATIC™ 60 offers possibilities to connect up to 8 units to allow relationship between each unit in order to
perform the system.
The pLAN bus is connected to Climatic™60 on the J8 connector of board BM60. A star connection is not
recommended. For an optimum operation it is advised to connect a maximum of two cables per unit.
The cable length should not exceed 500m and must use a 2 pairs with general shield like LiYCY-P (0.34 mm²).
21.2 - Description
There are 2 different modes to manage the units (“Cascade” & “Backup”)
21.2 1 - The cascade mode :
Used to engage additional cooling / heating capacity in order to reach the water set point. The cascade operating
includes 2 modes:
1. Twin mode : the units work simultaneously in order to equalize the number of compressors stages to
perform the capacity of the unit. The control manages only the increasing of capacity. The decreasing of
stage(s) is controlled individually by each unit. As well the capacity power factor is controlled individually
on each unit according to its demand.
2. Chain mode : the units start one after the other in serial sequence. In case of evaporator pump(s) in the
unit, the pump(s) is engaged according to the demand of the system.
21.2.2 - The backup mode
Used to help the system in case of alarm(s) on the unit running. The unit in standby will start only if one of the other
unit(s) running is in alarm. In this case the unit in alarm will be stopped and replace by the one which was in
standby.
The CLIMATIC™ 60 manages also the rotation between the units declared. . In “Cascade” mode, that means that
the first unit to start will change every week. In “Rol.Backup” mode, the unit in “Backup” is swapped every week.
Example:
In case of 4 units, the rotation is as follow:
Week Example Unit rotation
Week (n modulo 5) Week 1 ….U1

U2

U3

U4

….
Week (n+1 modulo 5) Week 2 ….U4

U1

U2

U3

….
Week (n+2 modulo 5) Week 3 ….U3

U4

U1

U2

….
Week (n+3 modulo 5) Week 4 ….U2

U4

U3

U1

….
The unit selected in standby is the one which has the higher critical(s) alarm(s). In case of disconnection of the
slave(s) unit(s) (@pLAN = 2

8) from the master unit (@pLAN = 1) on the pLAN bus, the disconnected unit will
operate alone.