63
Residual risks
14.1.4 Backup master unit
It is possible to configure a unit as a back-up master, preven-
ting the interruption of certain modes should the master fail.
To configure a back-up master, dip-switch 3 of the S4 must
be set to On.
At start-up, the service parameters must be configured inde-
pendently on both the HMI of the master and the backup
master.
This can be done by setting the former and copying the
parameters to the back-up unit via USB. This is the only way
to ensure that when the master fails, the other will provide
the system with the same pre-loaded functions.
Switching from the Master to the Back-up Master will only
take place in the event of major system alarms and only the
status (On/Off), Mode (Hot/Cold) and setpoint operation
parameters are copied. The remaining user setting parame-
ters are not transferred to the system in case of problems.
It is therefore advisable to copy that set on the Master to
the back-up master on a regular basis to prevent loss of the
desired settings.
Connection diagram of the electrical control system for the cascade system (three-phase)
Master unit
Slave unit 1
H1 H2
Slave unit 2
H1 H2
Slave unit x
H1 H2
......
L1 L2 L3 N
L1
L2 L3 N
L1
L2 L3 N
L1
L2 L3 N
ON
OFF
SW9
Slave unit
Master unit
T1 T2
X/HA Y/HB
Use shielded wire, the shielding layer must be earthed
Distribution
panel
Distribution
panel
Distribution
panel
External electric heater
Distribution
panel
On/Off
switch
Power supply
Only the last IDU requi-
res the addition of the
heater
H1-H2
......
Power supply
On/Off
Manual switch
Wire distribution box
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