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Siemens 3RU2126-4NC1 — Overload Relays

Siemens 3RU2126-4NC1 SIRIUS thermal overload relay, S0, 15 k

MPN3RU2126-4NC1
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Siemens SIRIUS 3RU2126-4NC1 thermal overload relay, size S0, Trip Class 10, 15 kW at 400 V, 690 V rated, spring-loaded terminals, integrated auxiliary switch.

Source DocumentedChannel stated on listing & quote
Condition PhotosReal unit photos / video on request
WhatsApp AnswersFast human replies for machine-down parts
Worldwide DispatchDHL/FedEx — transit quoted per order
Independent China distributor & sourcing agent· Listing updated Sep 2026

Specifications

3RU2126-4NC1 — Identification
ParameterValue
Product brand nameSIRIUS
Product designationthermal overload relay
Frame size (overload relay)S0
Combinable contactor sizesS0
Reference code (IEC 81346-2)F
3RU2126-4NC1 — Protection & Trip
ParameterValue
Overload current setting range23 ... 28 A
Trip classCLASS 10
Overload release typethermal
3RU2126-4NC1 — Electrical (main circuit)
ParameterValue
Rated operational current28 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 circuitspring-loaded terminals
Power loss at rated current (hot)9.6 W
Per pole3.2 W
3RU2126-4NC1 — 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
3RU2126-4NC1 — Connection & Mounting
ParameterValue
Mounting / fastening methodstand-alone installation
Mounting positionany
Main-circuit connector arrangementTop and bottom
Auxiliary/control circuit connection typespring-loaded terminals
Removable aux./control terminalNo
Conductor cross-section: solid or stranded2x (0.5 ... 2.5 mm²)
Conductor cross-section: finely stranded with ferrule2x (0.5 ... 1.5 mm²), 2x (0.75 ... 2.5 mm²)
Conductor range (AWG), main contacts1x (18 ... 8)
Conductor range (AWG), auxiliary contacts2x (20 ... 14)
3RU2126-4NC1 — 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
3RU2126-4NC1 — Mechanical
ParameterValue
Width45 mm
Height114 mm
Depth95 mm

Product details

The relay is rated for 15 kW at 400 V and 22 kW at 690 V (AC-3e duty), with a maximum rated insulation voltage of 690 V.

The Trip Class 10 rating governs the thermal curve: it allows the motor to draw starting current for up to 10 seconds before the bimetallic strip trips. That suits motors that reach full speed within that window — standard squirrel-cage induction motors on centrifugal loads. For high-inertia loads (crushers, centrifuges) that need a longer acceleration ramp, a Class 20 or Class 30 relay would be required; this one will nuisance-trip on those. The power ratings are tied to specific voltages: 15 kW at 400 V, 18.5 kW at 500 V, and 22 kW at 690 V. The current ratings at 480 V and 600 V are both 28 A, which gives you the thermal setting range. The relay's rated insulation voltage is 690 V, so it can be used on 400 V, 480 V, 600 V, and 690 V systems without derating the insulation. The auxiliary switch is integrated — no separate add-on block needed. The switch ratings cover a wide control-voltage range: 2 A at 24 V, 3 A at 120 V, 2 A at 230 V, and 1 A at 400 V, among others. That means the same relay works in 24 VDC control circuits and 230 VAC panels without swapping the auxiliary contact block. Termination is spring-loaded (cage-clamp style), accepting 2× 0.5 to 2.5 mm² solid or stranded. No screw torque to verify — just strip to 8 mm and push in. The relay mounts in any position and is designed for stand-alone installation, not ganged to a contactor.

The relay carries a substance prohibition date of October 1, 2009, aligning with RoHS and REACH substance restrictions. Temperature compensation is active from -40 to +60 °C, so the thermal curve stays accurate across the typical industrial panel ambient.

Frequently asked questions

Where can I buy 3RU2126-4NC1 and how do I get a price?

This part is sourced to order against an RFQ through independent distribution. Availability and current pricing are confirmed at quote time — submit an RFQ for a firm price and lead time.

What is the closest functional alternative to 3RU2126-4NC1?

The 3RU2116-1FC1 is a smaller-frame SIRIUS overload relay (S00 size vs S0), so it will not physically fit the same contactor interface or mounting footprint. For a drop-in replacement without rewiring, stay with the S0 frame size in the 3RU2126 series.

What does the note 'for message Tripped' mean on 3RU2126-4NC1?

The note indicates that the integrated auxiliary switch changes state to signal a 'Tripped' condition — it is the normally-closed contact that opens when the relay trips, providing a status signal to a PLC or indicator light.

What is the depth of 3RU2126-4NC1?

The depth is 95 mm, with a width of 45 mm and height of 114 mm. This is the S0 frame size — it mounts on DIN rail or directly with screws.

Will 3RU2126-4NC1 drop into a panel wired for 3RU2116-1FC1?

No — the 3RU2116-1FC1 is an S00 frame size with different mounting hole spacing and terminal layout. The S0 frame of the 3RU2126-4NC1 is physically larger and will not align with the existing footprint without panel modifications.

What compliance documentation does Siemens provide for 3RU2126-4NC1?

The relay carries a substance prohibition date of October 1, 2009, indicating RoHS and REACH compliance. Standard Siemens documentation includes the declaration of conformity and environmental product declaration.

MPN
3RU2126-4NC1