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Siemens 3RU2126-4CJ0 — Overload Relays

Siemens 3RU2126-4CJ0 SIRIUS thermal overload relay, S0, CLAS

MPN3RU2126-4CJ0

Siemens SIRIUS 3RU2126-4CJ0 thermal overload relay, size S0, CLASS 10, contactor mounting, 690 V rated, 85 x 45 x 85 mm.

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

Specifications

3RU2126-4CJ0 — Identification
ParameterValue
Product brand nameSIRIUS
Product designationthermal overload relay
Frame size (overload relay)S0
Combinable contactor sizesS0
Reference code (IEC 81346-2)F
3RU2126-4CJ0 — Protection & Trip
ParameterValue
Overload current setting range17 ... 22 A
Trip classCLASS 10
Overload release typethermal
3RU2126-4CJ0 — Electrical (main circuit)
ParameterValue
Rated operational current22 A
Poles (main circuit)3
Rated operating frequency50 ... 60 Hz
Rated insulation voltage (AC, pollution degree 3)690 V
Rated value (AC-3e), max.690 V
Rated surge withstand voltage6 kV
Main current circuitRing cable lug connection
Power loss at rated current (hot)8.1 W
Per pole2.7 W
3RU2126-4CJ0 — Auxiliary contacts
ParameterValue
Auxiliary contacts: NO1
Auxiliary contacts: NC1
Auxiliary contacts: CO (changeover)0
Auxiliary switch short-circuit protection (required fuse)fuse gG: 6 A, quick: 10 A
Switching current at 24 V2 A
Switching current at 60 V0.3 A
Switching current at 110 V0.22 A
Switching current at 120 V3 A
Switching current at 125 V0.22 A
Switching current at 220 V0.11 A
Switching current at 230 V2 A
Switching current at 400 V1 A
3RU2126-4CJ0 — Connection & Mounting
ParameterValue
Mounting / fastening methodContactor mounting
Mounting positionany
Main-circuit connector arrangementTop and bottom
Auxiliary/control circuit connection typering terminal lug connection
Removable aux./control terminalNo
3RU2126-4CJ0 — Environmental
ParameterValue
Operating temperature-40 ... +70 °C
Storage temperature-55 ... +80 °C
Transport temperature-55 ... +80 °C
Relative humidity, operating10 ... 95 %
Max. installation altitude2 000 m
3RU2126-4CJ0 — Mechanical
ParameterValue
Width45 mm
Height85 mm
Depth85 mm

Product details

Rated for 690 V, it handles motor loads up to 11 kW at 400 V and 18.5 kW at 690 V. The thermal bimetallic release is temperature-compensated from -40 to +60 °C, so the trip curve stays consistent whether the panel is in a cold warehouse or a hot machine room.

Mounts directly onto a contactor via the contactor mounting fastening method — no DIN rail required, though the S0 footprint is standard for the SIRIUS family. Main circuit connections use ring cable lugs (M4 screw size), and the auxiliary switch is integrated. A Pozidriv PZ 2 screwdriver with a 5–6 mm shaft diameter is what you'll need for the terminals.

The switching ratings across the voltage range tell you what auxiliary contacts can handle: 2 A at 24 V, 3 A at 120 V, 2 A at 230 V, 1 A at 400 V, 0.75 A at 690 V. These are for the integrated auxiliary switch, not the main motor circuit — the main path is rated for the full motor kW figures above. If you're using the auxiliary contact to signal a PLC input, check the voltage and current draw against these numbers. Trip class CLASS 10 is the key selection parameter: it matches standard squirrel-cage motor starting profiles. If your application has a long acceleration time (high-inertia loads like fans or flywheels), you'd typically step up to CLASS 20 or CLASS 30 — but for most conveyors, pumps, and compressors, CLASS 10 is the right call.

Frequently asked questions

What does the note 'for message Tripped' mean?

The note indicates this thermal overload relay includes an integrated auxiliary contact that changes state when the relay trips, providing a 'tripped' signal — typically wired to a PLC input or indicator lamp for remote fault annunciation.

MPN
3RU2126-4CJ0