Configuration
4.6 Load feeders - protection against short circuit
SIRIUS 3RM1 motor starter
76 Manual, 06/2016, A5E0345285095020A/RS-AE/005
Configuring a group of load feeders (group installation)
A "group installation" is a combination of several 3RM1 motor starters with one common
short-circuit protection device (branch circuit protection device). This common branch circuit
protection device can be a circuit breaker according to UL489, e.g. a 3RV27 or fuses
according to UL248.
The 3RM19 infeed system is suitable for a group installation according to UL because it can
be loaded up to a total current of 16 A. As an alternative, distribution of the main circuit can
be realized with individual cables that have an AWG 12 cross-section or with infeed system
16 A, with a different distribution, for example, "Power Distribution blocks" 5ST2-5
distribution blocks. Whether loading with a total current of >16 A is possible depends on the
tested assembly.
For further information, see Certificate of Compliance CoC
(https://support.industry.siemens.com/cs/ww/en/view/66427510).
SCCR short-circuit current rating
The SCCR (short circuit current rating) indicates the maximum permissible short-circuit
current for a switching device. A higher value can only be achieved in conjunction with
protection devices such as fuses or circuit breakers.
This rating is required for mounting accessories in control cabinets (control panels)
conforming to UL 508a. The switchgear assembly with the lowest value specifies the value
for the entire control panel.
Circuit breakers for protecting against short-circuit currents
Hazardous voltage at the motor
Will cause death, serious injury, or damage to property.
Health hazard from automatic hot restart.
The 3RM1 motor starter and the safety function must be checked after every tripping of the
motor starter protector (also in the case of overload).
Replace a defective 3RM1 motor starter including the terminals after a short circuit. With
3RM11 / 3RM13 Failsafe motor starters, you must check the safety functions in addition to
replacing the unit.
Standard short circuit according to UL 508 for 460 V + 5 %
Table 4- 14 Circuit breakers for protecting against short-circuit currents
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