The Siemens 3RH2140-1KB40 is a SIRIUS 3RH2 coupling contactor relay designed for switching auxiliary circuits in industrial automation and control systems. It features 4 normally open (4 NO) contacts, a 24 V DC low-power coil, an integrated suppressor diode, and screw-terminal connections. Siemens specifies this model as a Size S00 coupling contactor relay suitable for PLC outputs.
The relay is particularly suitable for PLC-controlled systems where low control-power requirements, reliable auxiliary switching and direct interfacing with PLC outputs are important.
The 3RH2140-1KB40 belongs to the Siemens SIRIUS 3RH2 contactor relay family, which is designed for switching control and auxiliary circuits rather than directly switching high-power motor loads.
As a coupling relay, it can provide electrical isolation and interface functionality between a PLC output or another control signal and downstream auxiliary circuits.
Typical applications include:
PLC output interfacing
Industrial automation
Machine-control panels
Control cabinets
Auxiliary circuit switching
Relay logic
Electrical interlocking
Signalling circuits
OEM machinery
Process automation
The 3RH2140-1KB40 uses a 24 V DC coil with a reduced control-power design. Siemens specifies the permissible operating range as 0.7 to 1.25 × Us and identifies the coil as suitable for PLC outputs.
The rated coil voltage is 24 V DC.
This makes the relay well suited to control systems where the output device has limited switching power and where efficient coil operation is desirable.
The relay includes an integrated suppressor diode across the DC coil. This helps limit voltage transients generated when the coil is de-energized and supports suitable interfacing with electronic control outputs.
This is particularly useful in PLC-based control panels where the relay is directly interfaced with electronic output modules.
The 3RH2140-1KB40 provides 4 normally open auxiliary contacts.
All four contacts are specified as instantaneous NO contacts.
These contacts can be used for:
Auxiliary switching
PLC signal transfer
Contactor control
Status signalling
Electrical interlocking
Machine sequencing
Control logic
Interface circuits
The combination of four NO contacts allows one relay to handle multiple auxiliary control functions within the same panel.
The 3RH2140-1KB40 uses screw-type terminals for its auxiliary and control circuits.
This provides a conventional wiring method familiar to electrical panel builders and maintenance teams.
The specified conductor capability supports practical industrial control-panel wiring and commissioning.
A key feature of the 3RH2140-1KB40 is its suitability for PLC outputs. Siemens specifically identifies the device as suitable for PLC output applications.
This makes it useful when a PLC needs to control multiple auxiliary switching paths through a compact relay interface.
Typical applications include:
PLC-controlled contactors
Solenoid interface circuits
Auxiliary relay switching
Machine-status control
Control-system isolation
Industrial signalling
The actual PLC output module must be checked for compatibility with the relay's 24 V DC coil characteristics.
The 3RH2140-1KB40 uses the compact S00 frame size.
Its compact dimensions make it suitable for control cabinets where efficient use of DIN-rail and panel space is important. Siemens specifies a width of approximately 45 mm for the device.
The relay can be installed using screw or snap-on mounting on a 35 mm DIN rail.
Siemens specifies the 3RH2140-1KB40 as not expandable with an auxiliary switch.
The four integrated NO contacts therefore provide the available auxiliary-contact configuration for this particular article.
The 3RH2140-1KB40 can be used in a wide range of control and automation systems.
It can act as a coupling relay between PLC outputs and downstream auxiliary circuits.
The four NO contacts can support machine sequencing, signalling and auxiliary control functions.
It can be used for auxiliary control and interlocking around motor starters and contactors.
The relay can provide switching interfaces for control-system commands and process equipment.
Its compact S00 format and low-power 24 V DC coil make it suitable for standardized OEM machine-control designs.
The 3RH2140-1KB40 is suitable for OEM machine manufacturers, electrical panel builders, automation integrators and industrial maintenance professionals.
Its combination of 4 NO contacts, 24 V DC low-power coil, integrated suppressor diode, PLC compatibility and screw terminals makes it a practical coupling relay for industrial control panels.
Siemens SIRIUS 3RH2 coupling contactor relay
Article number 3RH2140-1KB40
4 NO instantaneous contacts
24 V DC coil
Low-power coil design
Integrated suppressor diode
Screw-terminal connections
Size S00
Suitable for PLC outputs
Not expandable with auxiliary switch
Suitable for auxiliary circuit switching
Suitable for industrial automation
Suitable for OEM control panels
Low-power 24 V DC coil: Suitable for electronic control outputs and PLC interfaces.
Integrated suppressor diode: Helps reduce coil-related voltage transients.
4 NO contacts: Provides multiple auxiliary switching paths.
PLC compatibility: Designed for suitable PLC output applications.
S00 compact size: Helps optimize control-panel space.
Screw terminals: Provides a familiar industrial wiring method.
DIN-rail mounting: Supports practical control-panel installation.
Reliable coupling function: Helps interface electronic control signals with auxiliary circuits.
The Siemens 3RH2140-1KB40 combines a 24 V DC low-power coil, four instantaneous NO contacts and an integrated suppressor diode in a compact S00 coupling relay. Siemens specifically identifies it as suitable for PLC outputs, making it a practical interface component for modern industrial automation systems.
Its screw-terminal design and compact DIN-rail mounting make it suitable for OEM control panels, automation cabinets, PLC interfaces and auxiliary switching applications.
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It is a Siemens SIRIUS 3RH2 coupling contactor relay with 4 NO contacts and a 24 V DC low-power coil.
It has 4 normally open instantaneous contacts.
The rated coil voltage is 24 V DC.
Yes. The relay has an integrated suppressor diode.
Yes. Siemens specifically identifies the 3RH2140-1KB40 as suitable for PLC outputs.
Yes. It uses screw-type terminals for the auxiliary and control circuits.
It is a compact S00-size relay.
No. Siemens specifies this article as not expandable with an auxiliary switch.
It can be used in PLC interfaces, industrial automation, machine-control panels, auxiliary switching systems, interlocking circuits and OEM control cabinets.
You can explore the Siemens product range at SB Smart for Siemens coupling relays, contactor relays, auxiliary contact blocks and other industrial automation products.
| Specification | Details |
|---|---|
| Product Name | Coupling Contactor Relay |
| Manufacturer | Siemens |
| Brand | Siemens |
| Series | SIRIUS 3RH2 |
| Model Number | 3RH2140-1KB40 |
| SKU | 3RH2140-1KB40 |
| Product Type | Auxiliary Contactor / Coupling Relay |
| Contact Configuration | 4NO |
| Number of Normally Open Contacts | 4 |
| Number of Normally Closed Contacts | 0 |
| Frame Size | S00 |
| Control Supply Voltage | 24V DC |
| Coil Type | Low Power Consumption Coil |
| Power Consumption | 2.8 W |
| Operating Range | 0.7 – 1.25 × Us |
| Overvoltage Protection | Integrated Suppressor Diode |
| Connection Type | Screw Terminals |
| Suitable for PLC Outputs | Yes |
| Expandable with Auxiliary Contacts | No |
| Rated Operational Current AC-12 | 10 A |
| Rated Operational Current AC-15 at 230V | 10 A |
| Rated Operational Current AC-15 at 400V | 3 A |
| Rated Insulation Voltage (Ui) | 690 V |
| Rated Impulse Withstand Voltage (Uimp) | 6 kV |
| Protection Class | IP20 |
| Operating Temperature | -25°C to +60°C |
| Storage Temperature | -55°C to +80°C |
| Standards | IEC 60947-1, IEC 60947-4-1, IEC 60947-5-1 |
| Mounting Type | DIN Rail / Panel Mount |
| Applications | PLC Interface, Control Circuits, Automation Systems |
| Product Family | Siemens SIRIUS Coupling Relays |
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