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SENTRYUM EMERGENCY SUPPLY SINGLE PHASE - CBM
EXTERNAL PROTECTIVE DEVICES
RCD BREAKER (RESIDUAL CURRENT DEVICE)
If an input isolation transformer is not present, the neutral from the mains power supply is connected to the CSS output neutral. As a
result, there will be no change to the neutral arrangements of the installation:
THE CSS INPUT NEUTRAL IS CONNECTED TO THE CSS OUTPUT NEUTRAL
THE DISTRIBUTION SYSTEM THAT POWERS THE CSS IS NOT MODIFIED BY THE CSS
The neutral condition is only modified if an isolation transformer is present or when the CSS works with the neutral
isolated upstream.
Make sure that the equipment is properly connected to the input neutral, otherwise serious damage can occur
to the CS
.
During normal operation, when the mains supply is present, an RCD breaker at the input of the CSS will activate if a fault occurs at
the output side, since the output circuit is not isolated from the input.
In any case, other RCD breakers may still be installed at the output, preferably in coordination with those present at the input.
The earth leakage current may exceed 3.5mA (max 15mA), so the RCD breaker located upstream must have the following
characteristics:
Differential current adjusted to the sum of CSS + Load; we recommend keeping a suitable margin to prevent nuisance tripping
(100mA min. - 300mA recommended)
Type B
Delay of at least 0.1s
NOTE for DUAL INPUT connection:
1. A single RCD breaker must be installed upstream at the point where the sources divide to supply the standard input and the
bypass input of the CSS (refer to 22).
2. If the standard input and the bypass input are supplied from two separated sources, then it is required to use a dedicated
RCD device for each source.
BACKFEED PROTECTION
The CSS has an internal protection against backfeed. This protection acts by means of a sensing circuit which turns the inverter off if
a fault within the static switch is detected. During this condition, to avoid interrupting the supply to the connected load, the CSS
switches to the bypass line.
If this fault occurs during battery operation, the inverter is stopped.
A volt free contact can be configured to drive a disconnecting device to be installed upstream of the bypass input to the CSS, in this
case when a backfeed fault occurs, the system opens the external disconnecting device, hence avoiding the requirement to stop the
inverter (refer to the user manual to configure this option).
The label supplied with the CSS named “Risk of Voltage Backfeed” and included in the accessory box, must be affixed
to all disconnectors installed within the electrical system upstream of the CSS.
THERMAL-MAGNETIC CIRCUIT BREAKERS
As previously explained, the CSS has protection devices for output faults as well as for internal faults.
In order to configure the power source, a thermal-magnetic switch must be installed upstream of the CSS.
Please follow the indications in the table below:
Automatic external protective devices
Table 12
CSS Model
Mains input
Bypass Input (P+N)
Single-phase input (P+N) Three-phase input (3P+N)
6 63A (trip characteristic curve “C”) 20A (trip characteristic curve “C”) 40A (trip characteristic curve “D”)
8 80A (trip characteristic curve “C”) 25A (trip characteristic curve “C”) 50A (trip characteristic curve “D”)
10 80A (trip characteristic curve “C”) 40A (trip characteristic curve “C”) 63A (trip characteristic curve “C”)
15 100A (trip characteristic curve “C”) 50A (trip characteristic curve “D”) 100A (trip characteristic curve “C”)
20 125A (trip characteristic curve “C”) 50A (trip characteristic curve “D”) 100A (trip characteristic curve “C”)
If the protective device upstream of the CSS interrupts the neutral wire, it must also interrupt all of the phase wires at
the same time (4-pole breaker).
Please select the thermal-magnetic circuit breakers in accordance with the “SHORT CIRCUIT WITHSTANDING” below.
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