Siemens 5SU9356-1KK25 RCBO for Small Power Equipment Protection 25A 30mA 1P+N C

The Siemens 5SU9356-1KK25 RCBO stands as a crucial protective device for small power equipment, offering combined overcurrent and earth leakage protection in a compact 1P+N configuration. This unit, rated at 25A with a 30mA sensitivity, integrates the functions of a miniature circuit breaker (MCB) and a residual current device (RCD) into a single pole-and-neutral package, simplifying installation and reducing panel space. Its C-curve tripping characteristic ensures it can handle moderate inrush currents without nuisance tripping, making it suitable for inductive loads commonly found in small power applications. Key advantages include enhanced safety through reliable fault detection, compliance with stringent electrical safety standards, and efficient protection against electrical fires and electric shock hazards.

Product Specifications

| Specification             | Value                               |

| :------------------------ | :---------------------------------- |

| Product Type              | RCBO (Residual Current Breaker with Overcurrent Protection) |

| Manufacturer              | Siemens                             |

| Model Number              | 5SU9356-1KK25                       |

| Rated Current (In)        | 25 A                                |

| Rated Residual Operating Current (IΔn) | 30 mA                               |

| Number of Poles           | 1P+N (Single Pole + Neutral)        |

| Tripping Characteristic   | C-Curve                             |

| Rated Voltage (Ue)        | 230/400 V AC                        |

| Rated Breaking Capacity (Icn) | 6 kA                                |

| Frequency                 | 50/60 Hz                            |

| Terminal Type             | Screw Terminals                     |

| Mounting Type             | DIN Rail (35mm)                     |

| Ambient Temperature Range | -25°C to +45°C                      |

| Protection Class          | IP20 (Enclosure), IP40 (Terminal)   |

Core Features & Market Positioning

The Siemens 5SU9356-1KK25 RCBO distinguishes itself through its robust Siemens engineering, ensuring high reliability and consistent performance in demanding environments. As a Type A residual current device, it offers enhanced protection against both sinusoidal AC residual currents and pulsating DC residual currents, a critical feature for modern electronic equipment that may generate such fault currents. This duality positions it as a superior choice over simpler RCDs or MCBs, providing comprehensive protection against electric shock and fire. Its compact 1P+N design streamlines electrical panel assembly, saving valuable space and reducing installation time, a significant benefit in space-constrained applications or when retrofitting existing systems. The C-curve tripping characteristic provides a balance between overcurrent protection and the ability to withstand transient inrush currents, a common requirement for motors, transformers, and other inductive loads in small power circuits.

Key Application Scenarios

This Siemens RCBO is specifically engineered for the protection of circuits supplying small power equipment, such as lighting circuits, socket outlets, and appliances in residential, commercial, and light industrial settings. It is ideal for protecting individual circuits where both overcurrent (short-circuit and overload) and earth leakage faults pose significant risks. Common applications include domestic installations for kitchen appliances, entertainment systems, and HVAC units, as well as in commercial buildings for office equipment, server racks, and specialized machinery. Its 30mA residual current sensitivity makes it particularly effective in preventing electric shock by quickly disconnecting power upon detecting potentially dangerous leakage currents, safeguarding personnel and preventing damage to sensitive electronic devices. The 25A rating is well-suited for circuits with moderate power demands, ensuring operational continuity while providing essential safety.

Practical System Integration Guidance

Integrating the Siemens 5SU9356-1KK25 RCBO into existing or new electrical systems is straightforward due to its standard DIN rail mounting and familiar terminal layout. For installation, ensure the main power supply to the circuit is de-energized. The line (phase) conductor and neutral conductor from the incoming supply are connected to the corresponding L and N terminals on the RCBO, typically marked with upward arrows indicating supply. The outgoing conductors for the protected circuit are then connected to the load terminals. It is imperative to ensure correct polarity; connecting the neutral incorrectly can render the residual current protection ineffective. The device is designed for secure termination with standard electrical cables, and appropriate torque should be applied to the screw terminals to ensure a reliable connection and prevent overheating. Ensure the upstream overcurrent protection (if any, though the RCBO itself provides this) is adequately rated.

Operation and Risk Mitigation

The Siemens 5SU9356-1KK25 RCBO operates by continuously monitoring the current flowing through the phase and neutral conductors. If an imbalance occurs—indicating current is leaking to earth, often through a person or a faulty appliance—the device will rapidly trip, interrupting the power supply. This 30mA sensitivity is classified as "high sensitivity" and is crucial for protecting against direct contact with live parts, significantly reducing the risk of fatal electric shock. Overload protection is provided by the thermal tripping mechanism, which responds to sustained overcurrents, while short-circuit protection is handled by the magnetic tripping mechanism, which reacts instantaneously to very high fault currents. Common troubleshooting involves checking for persistent earth faults, ensuring correct wiring, and verifying that the circuit load does not exceed the 25A rating. Nuisance tripping can occur with inductive loads that have high inrush currents exceeding the C-curve's threshold; in such cases, a higher C-curve rating or an RCBO with a delayed tripping characteristic might be considered, though this specific model is optimized for small power equipment where such events are typically managed by its C-curve.

Scalability & Long-Term Value

The Siemens 5SU9356-1KK25 RCBO is designed for long-term reliability and offers excellent compatibility within Siemens' broader range of electrical protection and automation components. While not directly a digital or IIoT device, its integration into a smart electrical system is achieved through its dependable performance and standard form factor. It seamlessly fits into standard distribution boards and control panels, allowing for easy replacement or addition of protection devices. Its value lies in its robust construction and the assurance of protection it provides for sensitive and essential small power equipment, minimizing downtime and preventing costly damage. For systems requiring more advanced monitoring or remote control, this RCBO can be part of a larger system where upstream or downstream devices offer smart capabilities, ensuring fundamental safety while enabling broader system intelligence.

FAQs

What is the primary function of the Siemens 5SU9356-1KK25 RCBO?

The Siemens 5SU9356-1KK25 RCBO provides combined overcurrent and earth leakage protection for circuits. It acts as both a miniature circuit breaker (MCB) and a residual current device (RCD) in one unit. This ensures safety against electrical shocks and prevents damage from overloads or short circuits.

How does the 30mA sensitivity of the 5SU9356-1KK25 protect users?

A 30mA residual current sensitivity is considered high and is critical for personal protection against electric shock. If current leaks to earth, it swiftly disconnects the power. This rapid response significantly reduces the risk of serious injury or fatality from accidental contact.

What does the C-Curve tripping characteristic mean for this RCBO?

The C-Curve designation indicates the RCBO can handle higher inrush currents common with inductive loads. This prevents nuisance tripping for devices like motors or transformers. It balances sensitivity for fault protection with tolerance for temporary current surges.

Can the Siemens 5SU9356-1KK25 be used for both residential and industrial applications?

Yes, this RCBO is suitable for a range of applications, including residential and light industrial uses. It is ideal for protecting circuits supplying common appliances and equipment in homes, offices, and workshops. Its compact design is a significant advantage in panel space.

What is the significance of the 1P+N configuration for this device?

The 1P+N (Single Pole + Neutral) configuration means it protects and disconnects both the live (phase) and neutral conductors. This is crucial for comprehensive circuit protection. It simplifies wiring and reduces the number of components needed in a single-phase circuit.

What is the breaking capacity of the 5SU9356-1KK25, and why is it important?

The 5SU9356-1KK25 has a rated breaking capacity (Icn) of 6 kA. This is the maximum fault current it can safely interrupt without being damaged. A higher breaking capacity is essential in areas with potentially high fault currents to ensure reliable protection and safety.

What type of residual current does the 5SU9356-1KK25 detect?

This RCBO is a Type A device. It detects sinusoidal AC residual currents and pulsating DC residual currents. This is important for modern electronics that can produce pulsating DC leakage, offering broader protection than older Type AC devices.

How is the Siemens 5SU9356-1KK25 typically installed?

It is designed for easy installation on a standard 35mm DIN rail within electrical distribution boards. Line and neutral conductors are connected to the input terminals, and the circuit's outgoing conductors connect to the output terminals. Ensure power is off before installation.

What are the environmental operating conditions for this RCBO?

The 5SU9356-1KK25 is rated for ambient temperatures between -25°C and +45°C. It also has specific enclosure and terminal protection ratings (IP20/IP40) suitable for typical indoor electrical installation environments. Avoid exposure to excessive moisture or dust.

Where can I find replacement parts or additional technical documentation for this product?

For replacement parts or detailed technical documentation, including datasheets and installation manuals, you should consult the official Siemens industry or automation product portal. Authorised Siemens distributors are also a primary source for support and component information.