Siemens 3RU2126-4DC0 SIRIUS Thermal Overload Relay, CLASS 10

Name: 3RU2126-4DC0
Brand: Siemens
SKU: 3RU2126-4DC0
Availability: LimitedAvailability
Author: Storeroom Stan

Specifications

Identification

3RU2126-4DC0 — Identification
Parameter	Value
Product brand name	SIRIUS
Product designation	thermal overload relay
Frame size (overload relay)	S0
Combinable contactor sizes	S0
Reference code (IEC 81346-2)	F

Protection & Trip

3RU2126-4DC0 — Protection & Trip
Parameter	Value
Overload current setting range	20 ... 25 A
Trip class	CLASS 10
Overload release type	thermal

Electrical (main circuit)

3RU2126-4DC0 — Electrical (main circuit)
Parameter	Value
Rated operational current	25 A
Poles (main circuit)	3
Rated operating frequency	50 ... 60 Hz
Rated insulation voltage (AC, pollution degree 3)	690 V
Rated value (AC-3e), max.	690 V
Rated surge withstand voltage	6 kV
Main current circuit	spring-loaded terminals
Power loss at rated current (hot)	8.1 W
Per pole	2.7 W

Auxiliary contacts

3RU2126-4DC0 — 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 gG: 6 A, quick: 10 A
Switching current at 24 V	2 A
Switching current at 60 V	0.3 A
Switching current at 110 V	0.22 A
Switching current at 120 V	3 A
Switching current at 125 V	0.22 A
Switching current at 220 V	0.11 A
Switching current at 230 V	2 A
Switching current at 400 V	1 A

Connection & Mounting

3RU2126-4DC0 — Connection & Mounting
Parameter	Value
Mounting / fastening method	Contactor mounting
Mounting position	any
Main-circuit connector arrangement	Top and bottom
Auxiliary/control circuit connection type	spring-loaded terminals
Removable aux./control terminal	No
Conductor cross-section: solid or stranded	2x (0.5 ... 2.5 mm²)
Conductor cross-section: finely stranded with ferrule	2x (0.5 ... 1.5 mm²), 2x (0.75 ... 2.5 mm²)
Conductor range (AWG), main contacts	1x (18 ... 8)
Conductor range (AWG), auxiliary contacts	2x (20 ... 14)

Environmental

3RU2126-4DC0 — Environmental
Parameter	Value
Operating temperature	-40 ... +70 °C
Storage temperature	-55 ... +80 °C
Transport temperature	-55 ... +80 °C
Relative humidity, operating	10 ... 95 %
Max. installation altitude	2 000 m

Mechanical

3RU2126-4DC0 — Mechanical
Parameter	Value
Width	45 mm
Height	102 mm
Depth	84 mm

Product details

CLASS 10 trip curve and motor protection

The 3RU2126-4DC0: This is the standard trip class for general-purpose motor starting — it allows the motor to accelerate through inrush without nuisance tripping while still protecting against locked-rotor conditions. The 480 V and 600 V ratings both list 25 A, which matches the S0 frame size current ceiling.

S0 frame and contactor mounting

Size S0 overload relay, 45 mm wide, 84 mm deep, 102 mm tall. Mounts directly onto the matching SIRIUS contactor — no DIN rail bracket needed. The fastening method is contactor mounting, and the relay can be installed in any position.

Active production and sourcing

Temperature compensation is active from -40 to +60 °C, keeping the trip curve accurate across the typical panel environment.

Frequently asked questions

What does the 'Note for message Tripped' mean on the 3RU2126-4DC0?

The note indicates the relay has a built-in auxiliary contact that changes state when the overload trips, providing a signal that can be wired to a PLC input or indicator lamp for remote fault indication.

What is the depth of the 3RU2126-4DC0?

The depth is 84 mm, with a width of 45 mm and height of 102 mm. It mounts directly onto the SIRIUS contactor.