BOM / RFQ

3RB2123-4QB0 - Siemens

MPN3RB2123-4QB0

Overload relay 6...25 A For motor protection Size S0, class 5...30 Contactor mounting Main circuit: screw terminal Auxiliary circuit: screw terminal Manual-Automatic-Reset Internal ground fault detection!!! Phased-out product!!! Successor is SIRIUS 3RB3 Preferred successor type is >>3RB3123-4QB0<<

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Sourced new & surplus through independent channelsAuthenticity-screened · ESD-safe packingListing updated Jul 2026

Specifications

3RB2123-4QB0 — Identification
Parameter	Value
Product brand name	SIRIUS
Product designation	solid-state overload relay
Combinable contactor sizes	S0

3RB2123-4QB0 — Protection & Trip
Parameter	Value
Overload current setting range	6 ... 25 A
Trip class	CLASS 5E, 10E, 20E and 30E adjustable

3RB2123-4QB0 — Electrical (main circuit)
Parameter	Value
Poles (main circuit)	3
Rated insulation voltage (AC, pollution degree 3)	690 V
Rated surge withstand voltage	6 kV
Main current circuit	screw-type terminals
Power loss at rated current (hot)	0.05 W
Per pole	0.02 W

3RB2123-4QB0 — Auxiliary contacts
Parameter	Value
Auxiliary contacts: NO	1
Auxiliary contacts: NC	1
Auxiliary contacts: CO (changeover)	0
Auxiliary switch short-circuit protection (required fuse)	fuse gL/gG: 6 A
Switching current at 24 V	2 A
Switching current at 60 V	0.55 A
Switching current at 110 V	0.3 A
Switching current at 120 V	4 A
Switching current at 125 V	0.3 A
Switching current at 220 V	0.11 A
Switching current at 230 V	3 A

3RB2123-4QB0 — Connection & Mounting
Parameter	Value
Mounting / fastening method	Contactor mounting
Mounting position	any
Auxiliary/control circuit connection type	screw-type terminals
Conductor cross-section: solid	0.5 ... 4 mm², 2x (0.5 ... 2.5 mm²)
Conductor cross-section: finely stranded with ferrule	0.5 ... 2.5 mm², 2x (0.5 ... 1.5 mm²)
Conductor range (AWG), main contacts	2x (14 ... 10)
Conductor range (AWG), auxiliary contacts	2x (20 ... 14)

3RB2123-4QB0 — Environmental
Parameter	Value
Operating temperature	-25 ... +60 °C
Storage temperature	-40 ... +80 °C
Transport temperature	-40 ... +80 °C
Relative humidity, operating	100 %
Max. installation altitude	2 000 m
Shock resistance	15g / 11 ms