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Siemens 3RU2126-4PJ0 — Overload Relays

Siemens 3RU2126-4PJ0 SIRIUS thermal overload relay, Class 10

MPN3RU2126-4PJ0

Siemens SIRIUS thermal overload relay, 3RU2126-4PJ0, Class 10, Size S0, 690 V rated, 18.5 kW at 400 V, contactor mounting.

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

3RU2126-4PJ0 — Identification
ParameterValue
Product brand nameSIRIUS
Product designationthermal overload relay
Frame size (overload relay)S0
Combinable contactor sizesS0
Reference code (IEC 81346-2)F
3RU2126-4PJ0 — Protection & Trip
ParameterValue
Overload current setting range30 ... 36 A
Trip classCLASS 10
Overload release typethermal
3RU2126-4PJ0 — Electrical (main circuit)
ParameterValue
Rated operational current36 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)9.6 W
Per pole3.2 W
3RU2126-4PJ0 — 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
3RU2126-4PJ0 — 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
3RU2126-4PJ0 — 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
3RU2126-4PJ0 — Mechanical
ParameterValue
Width45 mm
Height85 mm
Depth85 mm

Product details

Rated at 690 V and sized for the S0 frame, this relay mounts directly onto a contactor of the same frame, keeping the panel wiring compact. The thermal release is temperature-compensated from -40 to +60 °C, so the trip point stays consistent whether the panel sits in a cold warehouse or a warm machine room.

The headline power rating is 18.5 kW at 400 V, which tells you the motor it can protect in a standard 400 V three-phase system — match this to your motor nameplate, not the contactor rating. At 480 V it carries 36 A; at 600 V the same 36 A, and at 690 V it handles 30 kW — the current limit is the same across the higher voltages, so the relay's thermal element is current-limited, not voltage-limited, above 480 V. The auxiliary switch is integrated — one normally-open and one normally-closed contact, rated at 2 A at 24 V, 3 A at 120 V, 2 A at 230 V, and 1 A at 400 V. That covers the feedback signal to the PLC or the trip indication lamp without an add-on block. The note "for message 'Tripped'" on the product line means the auxiliary contacts change state when the bimetals have reached the trip threshold — this is the signal you wire back to the control system to flag an overload condition.

Fastens directly onto the contactor — no DIN rail needed, which saves a slot in the panel. Mounting position is any orientation, so it fits in tight enclosures or vertical bus stacks. Main circuit connection is via ring cable lugs, M4 screws. The auxiliary wiring uses screw terminals; the screwdriver shaft should be 5 to 6 mm diameter with a Pozidriv PZ2 tip.

MTTF at high demand rate is 2,280 years. Because it is active and standard, lead time is typically the factory lead for the SIRIUS line — no broker or surplus premium involved.

Frequently asked questions

What does the note 'for message Tripped' mean?

It means the integrated auxiliary switch changes state when the bimetals reach the trip temperature, providing a signal to the control system that the relay has tripped on overload.

MPN
3RU2126-4PJ0