Siemens has introduced the SENTRON Electronic Circuit Protection Device (ECPD) to the UK market, offering a new approach to protecting low-voltage electrical systems with response times up to 1,000 times faster than conventional electromechanical circuit protection.

Designed for use in electrical distribution boards and control cabinets, the semiconductor-based device can reduce the energy released during a short circuit by up to 99.5%, helping to minimise equipment damage, reduce downtime and improve system resilience.

Combining circuit protection, switching, measurement and communication functions within a single unit, the SENTRON ECPD also enables remote diagnostics and switching, making it particularly well suited to remote or difficult-to-access installations. Siemens says the integrated design can reduce the space required within electrical panels by up to 80%, depending on the application.

The device forms part of the wider communication-enabled SENTRON portfolio and can be configured using the SENTRON Powerconfig app, while integration with SENTRON Powercenter gateways allows performance data and diagnostics to be monitored locally or in the cloud.

Jacob Wells, Product Manager at Siemens UK & Ireland, said: “As UK sites become more electrified and more connected, circuit protection needs to become smarter too. SENTRON ECPD gives installers, panel builders and operators a future-ready way to protect circuits, monitor performance and support uptime.”

Suitable for commercial, industrial and infrastructure applications, the SENTRON ECPD has been developed to help improve safety, simplify panel design and enhance the reliability of modern electrical installations.

For more information, visit: https://www.siemens.com

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Martin Plumbridge, Technical Manager at Doepke, discusses RCD protection and looks at whether an RCCB Type B trips on DC.

We have witnessed an increase in reports from several well-informed installers relating to Type B’s that do not function correctly in the presence of DC components. For example, one design was marked as bidirectional but failed smooth DC tripping test. Although the basic requirements of BS 7671 do not require verification that the Type B RCD protection feature works, it would seem prudent to spend a few minutes checking that modern complex domestic systems costing possibly £10,000 or more are protected by a functioning RCD. A simple test with the correct instrument can be performed to verify that the RCD trips when subject to smooth DC.

RCD tests and thresholds

The existing BS7671 1 x RCD verification test required for example for 30mA RCDs relates to an AC sinusoidal residual current, irrespective of the type of RCD.

• All RCCBs subjected to 50Hz residual current are designed to trip between >50% – <100% I∆n, which equates to 15 to 30mA. The max switch off time at 1 x is 0.3s.
• Type A, type F, and type B pulsed residual current (50Hz); the tripping current threshold changes to >35% – < 140% I∆n.

Type A (BS EN 61008-1) must still trip with the pulsed waveform superimposed on 6mA smooth DC.

Type F (BS EN 61008-1 and BS EN 62423) must still trip with the pulsed waveform superimposed on 10mA smooth DC.

Type B (BS EN 61008-1 and BS EN 62423) subjected to smooth DC residual current must trip between >50% – <200% I∆n i.e. for 30mA equates to 15 < 60mA DC on both cycles 0° and 180°.

The standards define the tripping thresholds and times based on the residual current components. Although BS 7671 only requires verification of the AC trip threshold irrespective of the type, Michael Peace’s IET Article in Issue 91 July 2022 explains that other tests are not precluded.

Why DC tripping characteristics matter

RCD Types A and F use a magnetic core to detect imbalance between live and neutral conductors. Smooth DC residual current above the design current can saturate this core, a phenomenon known as DC blinding.

When the core is saturated, The RCD becomes insensitive to further imbalance. Trip thresholds increase unpredictably; the device may fail to trip entirely. This is a major safety concern because a circuit could carry a dangerous fault current without any protective disconnection.

Type B RCDs are designed to detect smooth DC and trip when it exceeds the default value. This maintains sensitivity to both AC and pulsating DC components while also responding to pure DC leakage.

Test instruments

For test instruments equipped with a Type B RCD setting, a multiplier of 2 × I∆n is applied in accordance with the product standard BS EN 62423. We have witnessed an increase in complaints relating to a number of type B’s that do not function correctly in the presence of DC components. Particularly those that are marked as bidirectional. A simple test can be performed to verify DC tripping on DC currents.

Testing procedure for Type B RCDs

The testing procedure for a type B RCD is relatively straight forward from connecting the live, neutral and earth to probes the appropriate terminals on the load side and carrying out the tests. Once complete, carry out the same test on the supply side to check the device is true bidirectional.

• Carry out standard AC test first (following all testing safety procedures).
• DC Tripping test applicable to any 2-pole 30mA type B (Outgoing circuit should be disconnected).

To measure RCD tripping current on a Fluke 1654B

1. Turn the rotary switch to I∆n position.
2. press F1 to select the test current phase, 0° or 180°.
3. press F3 to select the RCD test-current waveform: smooth – DC current to test type B RCD.
4. press F4 to select the RCD current rating (10,30,100,300 or 500mA).
5. press and release ‘test. Wait for the test to complete.

Conclusion

So, does a Type B RCCB trip on DC? Well, the answer is that it should do but some don’t. If it is detecting DC it should trip between >50% – <200% I∆n, which equates to 15 to 60mA range on both cycles 0° and 180° for 30 mA device. If it is truly bi-directional it will trip on DC irrespective of which side, you connect the supply.

The testing procedure for a type B RCD including DC test takes a few minutes in addition to the standard AC test. If it is complex installation requiring Bi-directional RCD functionality you can verify the operation by repeating the test on the reverse side.

Spend a few additional minutes checking that your modern complex domestic system and the people using it are adequately protected by the RCD you have specified and installed.

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Click Scolmore has announced the launch of the Elucian Type B Heat Pump (HP) Bi-Directional RCCB, a high specification protective device designed to protect people and equipment by disconnecting the power supply when excess leakage current to earth is detected.

The new Elucian Type B HP RCCB builds on the capabilities of a standard Type B device by delivering enhanced sensitivity at higher frequencies. While a conventional Type B RCCB detects pure direct current from 0Hz upwards and alternating current leakage up to 1kHz, the Type B HP extends detection capability to 20kHz. This significantly broader detection range provides reliable protection in installations where high frequency leakage currents are present.

Enhancing Elucian’s growing circuit protection portfolio offerings, this advanced RCCB helps prevent electric shock and potential fire hazards, making it suitable for advanced residual current protection for modern high-performance electrical installations. Designed to detect high-frequency and DC leakage currents that standard RCCBs might miss, the new Type B HP provides reliable protection for these increasingly complex circuits.

The Elucian Type B RCCB is suitable for use across a wide range of applications, including EV charging installations, HVAC systems, elevators, pumps and heat pumps, and CNC machinery.

Find out more here

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Jake Green, Head of Technical Engagement, Scolmore Group, looks at how electrical faults can generate high fault currents — and why it’s crucial to ensure protective devices and switchgear are correctly rated to handle them.

In any electrical system, a fault – whether to Earth or between live conductors – will produce what’s known as a fault current. The level of this current depends on a range of factors, including system voltage, number of phases, and how close the installation is to the distribution transformer.

For wholesalers and contractors, understanding these fault levels is key to selecting and supplying the right equipment. This article explores typical fault current scenarios, how they can be assessed, and why choosing products with the correct breaking capacity is vital for safe and compliant installations.

In any electrical system a fault to Earth or a fault between live conductors will generate a fault current. The level of fault current will depend on a range of factors, including voltage levels, number of phases, proximity to the distribution transformer, and the like.

This article looks at likely levels of fault current, how they are to be assessed and the nature of equipment being sufficient to manage such fault currents (breaking capacity).

Types of fault

There are two types of ‘short circuit’ generally considered in BS 7671:

• Earth fault current – a current resulting from a fault of negligible impedance between a line conductor and an exposed-conductive-part or a protective conductor.
• Short circuit – an overcurrent resulting from a fault of negligible impedance between live conductors having a difference in potential under normal operating conditions.

Single-phase fault

Based on Figure 1 the level of fault current is determined by the following:

• The voltage – single phase (230 V)
• The impedance of the transformer winding
• The impedance of the supply cable (line-to-Earth or line-to-neutral)
• The impedance of the internal cable (line-to-Earth or line-to-neutral)

The simplest way to determine the level of fault current in a single-phase system is to determine the combined values of the transformer winding and the line and neutral conductors.

This can be simplified to

Two-phase fault

Based on Figure 1 the level of fault current is determined by the following:

• The voltage – between two phases (400 V)
• The impedance of the transformer winding.
• The impedance of the supply cable (line-to-Earth or line-to-neutral).
• The impedance of the internal cable (line-to-Earth or line-to-neutral.

The simplest way to determine the level of fault current between two-phases is to determine the combined values of the transformer winding and the line and line conductors.

This can be simplified to

The level of fault will be greater than for a single-phase fault but will not be double the value of a single-phase fault.

Three-phase fault

Based on Figure 1 the level of fault current is determined by the following:

• The voltage – counter-intuitively this is taken to be the value of a single-phase supply (230 V)
• The impedance of the transformer winding.
• The impedance of the supply cable (line only).

The simplest way to determine the level of fault current between three-phases is to determine the combined values of the transformer winding and the line conductor.

This can be simplified to

The level of fault will be greater than for a single-phase fault, and a two-phase fault but will still not be double the value of a single-phase fault.

Understanding the difference between expected fault current levels is important when selecting electrical equipment, such as circuit-breakers, switches and the like.

In a subsequent article we will consider the impact of prospective fault current values on the choice of equipment and recognise the importance of ensuring that the correct breaking capacity is selected.

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In this month’s Face to Face we speak with Alistair Eaton, Commercial Manager at Electrium, to hear about the evolution of the Crabtree brand.

• When was Crabtree founded and how has its product offering evolved over the years?

Crabtree was founded in 1919 by John Ashworth Crabtree in Walsall, UK, originally as J.A. Crabtree & Co. Ltd. Starting with light switches, the company quickly expanded into sockets, plugs, and power accessories, becoming a pioneer in electrical engineering. It introduced several industry firsts, including the “Quick Make & Break” switch and the UK’s first earth leakage circuit breaker. Over time, Crabtree diversified into switchgear, fusegear, motor control gear, and panelboards. The launch of Starbreaker in 1979 marked a major advancement in domestic circuit protection, followed by Polestar and Loadstar for commercial use. Since joining the Siemens-owned Electrium Group in 2006, Crabtree has continued to evolve, offering solutions across the residential and commercial sector, while maintaining its legacy of innovation, quality, and trusted performance.

• What are Crabtree’s core product ranges?

Crabtree offers a comprehensive range of circuit protection and power distribution products, spanning from 100A single-phase consumer units to 630A panelboards. At the heart of its domestic offering is the innovative Starbreaker range, known for its safety, compliance, and ease of installation. For commercial and light industrial applications, Loadstar and Polestar provide versatile three-phase distribution board solutions tailored to different installation needs. Fusestar delivers reliable fuse switch disconnection, while Powerstar completes the portfolio with robust panelboards designed for high-capacity installations up to 630A. Together, these ranges reflect Crabtree’s commitment to quality, innovation, and trusted performance across all sectors of the electrical industry.

• Does Crabtree still manufacture in the UK?

Crabtree is proud to still maintain a significant manufacturing footprint in the UK at our site at Hindley Green. We manufacture all our three phase distribution boards at the site alongside our Wylex and Siemens offering. We see manufacturing in the UK as hugely important to not only us but also to all our stakeholders, whether they be suppliers, distributors, specifiers or contractors. Our UK manufacturing facility empowers us to deliver exceptional quality, faster lead times, and a more resilient supply chain as well as supporting local employment, driving innovation, and supporting our sustainability goals.

• Since its launch in 1979 the Starbreaker brand has remained popular with installers and wholesalers – what makes it stand out in a crowded marketplace?

Starbreaker is Crabtree’s innovative circuit protection range, offering unmatched safety, reliability, and installation efficiency. Its unique plug-in busbar design reduces connections by 25%, lowering the risk of loose terminals and ensuring secure, consistent device fitting. The fully shrouded busbar provides insulation, preventing accidental contact, arcing, and incorrect device installation—key benefits for social housing and safety-focused projects. Designed for flexibility, Starbreaker supports both bespoke configurations and pre-assembled units, streamlining installation and saving time on site. It’s ideal for new builds and retrofits, with support for easy upgrades using the latest safety technologies such as surge protection, bidirectional AFDDs, and RCBOs. Built for longevity and compliance, Starbreaker continues to meet the evolving demands of modern electrical installations without compromising on performance.

• What does the future hold for the Crabtree brand?

Crabtree is synonymous with quality, innovation, and trusted performance and will continue to enhance its circuit protection portfolio with exciting new products, ensuring it remains the preferred choice for professionals seeking reliability, safety, and forward-thinking design.

Find out more about Crabtree UK here

Catch up on previous ‘Face to Face’ articles here

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The humble electrical fuse is often the unsung hero of circuit protection. Harsha Raghaven of Lawson Fuses explains why it remains such a vital component.

In the world of electrical engineering, circuit protection is a critical aspect that ensures the safety and longevity of electrical systems. Amongst the various methods of circuit protection, fuses have stood the test of time as one of the most reliable and essential components and have continued to do so, due to the constant review of international and local standards, improved design capability and modern manufacturing techniques.

It is a testament to the longevity of a type of component initially patented in 1890, with first British Standard getting released in 1919 and Lawson Fuses have been designing and manufacturing these fuses since 1938, with more demand for new types and higher quantities each year.

Protect and connect

Circuit protection involves the implementation of devices and mechanisms designed to prevent excessive current flow, which can cause overheating, fires, and damage to electrical components. The primary goal is to ensure that electrical systems operate within safe parameters, thereby protecting both the equipment and the users.

As electrical circuits become ever more complex, and regulations more stringent, there are many different circuit protection devices available, including circuit breakers, surge protectors, residual current devices and fuses. Each of these devices has its unique characteristics and applications, but fuses remain a fundamental component due to their simplicity, reliability, and effectiveness.

The silent guardian

A fuse is a simple yet ingenious device that consists of a metal element or wire that melts when excessive current flows through it. This melting action breaks the circuit, stopping the flow of electricity and preventing damage to the system. A lot of fuses are dual action, in that they will protect against low over currents but will also protect against massive currents generated by a short circuit failure. Fuses are designed to be the weakest link in an electrical circuit, ensuring that they will fail before any other component is damaged.

The key advantages of fuses include:

1. Speed: Fuses are generally faster than other protection devices for short circuit protection and will operate around 2ms, which is approximately 10 times faster than other types of protection.
2. Application: Whilst other protection devices are for low voltage protection only, fuses are suitable for very low and very high voltages, ranging from miniature devices for 230V up to full HV qualified fuses. The breaking capacity of a fuse will generally always be much higher. Typical breaking capacities are 80kA and 120kA, as opposed to typical ratings of 15kA for other devices.
3. Simplicity: Fuses are straightforward devices with no moving parts, making them easy to understand and use.
4. Reliability: Fuses provide consistent and predictable protection, as they are designed to operate under specific conditions.
5. Cost-Effectiveness: Fuses are generally inexpensive compared to other circuit protection devices, making them an economical choice for many applications.

For all the above reason, despite the development of more sophisticated circuit protection devices, fuses remain indispensable. Especially, like the one developed by Lawson Fuses; High Rupture Capacity (HRC) fuses are the backbone of industry protection as they offer such varied options for LV to HV, massive breaking capacities and offer protection against low current overloads and short circuit failures.

There is an enormous range of sizes and fittings available so there will always be a fuse that is suitable for your application, no matter how new or old your system is. Types include bolted, offset tags, slotted tags, cylindrical and square body with a choice of size depending on your current rating requirement.

Modern alternatives and their limitations

While modern alternatives like circuit breakers and electronic protection devices offer advanced features and greater flexibility, they also come with certain limitations:

• Complexity: Circuit breakers and electronic protection devices are more complex than fuses, requiring regular maintenance and calibration to ensure proper operation.
• Cost: These advanced devices are generally more expensive than fuses, which can be a significant factor in large-scale applications.
• Response Time: Although circuit breakers can offer adjustable trip settings, they may not always respond as quickly as fuses in certain overcurrent conditions.

Conclusion

In conclusion, fuses continue to be a vital component of circuit protection due to their simplicity, reliability, cost-effectiveness, and quick response time. The various fuse standard committees are highly active, and the IEC has released updated standards for LV fuses in the last couple of months.

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Click Scolmore has updated its ‘Wiring Accessories and Circuit Protection’ catalogue to include the latest product launches. Issue 15 is now available and brings together all products into one, easy to access reference guide.

It comprises of the latest additions across the Click range, including the new RCD sockets and LED indicator products to the Mode range. A new antique brass finish has been added to the Definity Complete range, plus new Part M unswitched sockets, as well as USB-C sockets and modules. Also added to the expanding Elucian circuit protection collection is a 25A rated RCBO, energy meters, and unpopulated consumer units.

Available to download from the Scolmore website, the new catalogue provides wholesalers, contractors, and specifiers with a valuable, in-depth resource to help them locate the right products and solutions for a variety of projects.

The catalogue is rich in product and technical information and features every product from each range that Click covers and incorporates all the latest additions that have been developed to meet the growing demand in the marketplace.

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When it comes to circuit protection, cutting corners can lead to serious consequences. Nico van der Merwe, VP Home & Distribution UK & Ireland at Schneider Electric, discusses the shortcuts that can lead to short-circuits and how you can avoid them.

A consumer unit is the electrical heart of the home and its vital responsibilities are often overlooked. The devices fitted within a consumer unit can help protect against electrical faults, such as overloads, short circuits, earth leakage, and arc faults. Without this protection, it could result in electric shocks and damage to the cable installation. Arcing can potentially damage cables over time, which leads to an increased risk of fire.

However, having a consumer unit doesn’t guarantee comprehensive protection for customers. Compliance with relevant standards and regulations, whilst considering the type and age of devices inside the unit, is key. Not only is compliance essential for the safety of the home in which the units are installed, the reputation of the businesses that sold, supplied, and installed them is at high risk of being tarnished too.

This highlights the importance of creating a thorough vetting process for consumer unit procurement, as well as checking compliance with the latest standards and getting regular checks of installations. As the consumer unit is the heart of everyone’s home, it is paramount that all the necessary steps are taken to ensure it is as safe as possible.

Don’t just go with the flow, go for those in the know

While there is a vast array of brands out there all vying to secure that position on a shelf within your branch, opting for the right manufacturer is critical not only for the safety of your customers and end users, but also for the reputation of your business. Compromising on quality could cause serious repercussions.

When making that decision on which manufacturer’s product you are going to stock, the quality of the product, the reputation of the manufacturer, as well as the availability of future support should all be considered before making your selection. Doing this will give you peace of mind that you have done as much as you can to ensure the safety of your customers and the end users.

So, what are the key things to look out for when selecting a manufacturer?

1. Go for those in the know– Looking for a manufacturer that specialises in circuit protection is maybe the most obvious tip, but it is the clearest way of knowing that the products they supply are high-spec and built to the latest industry standards.
2. BEAMA Membership– You would be surprised at the number of manufacturers that are not members of BEAMA, the UK’s trade association for electrical manufacturers and providers of energy infrastructure technologies and systems. Members of BEAMA are committed to building products in line with their high standards, allowing you to buy with added confidence.
3. Future Ready– Consumer units aren’t something that you rip out and replace every 2-3 years, they are a mainstay of a household’s electrical system. If an older unit needs to be repaired, your customers may need access to spare parts for products that may be 10-15 years old. In the same vein, a company that innovates its products to factor in potential future changes is one that you know has the market knowledge and experience to depend upon.

Taking these steps to assess your manufacturer of choice will not only give you clarity of choice in the short term, but it will enable you longer, healthier relationships with customers who experience fewer faults as a result of safer, more reliable equipment. A little knowledge and effort go a long way toward making sure your customers’ (and their customers’) needs are met.

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