Switching on to compliant Central Power Supply System

Switching on to compliant Central Power Supply System

With the global emergency lighting market predicted to grow to $7.1 billion by 20271, the importance of keeping employees and residents safe has never been more topical.Making sure that emergency lighting systems are designed and installed to the highest standards is key to ensuring that any failure risk is minimized. That is why it is crucial to make sure that the Central Power Supply System (CPS) is suitable for the project and will operate the complete installation safely and without interruption.

Why is a Central Power Supply system so important?

As the CPS is classified as a critical life safety system for the building, its design and function are governed by a set of standards, with EN 50171 being the main one.

A CPS is essentially a large set of batteries and control equipment at a single, central location. In the event of a mains failure in the building, the CPS is designed to provide reliable power backup for emergency lighting load, without any impact on the power output and thus playing an important part for a safe evacuation of the building's occupants.

EN50171 defines CPS as “a central power supply system which supplies the required emergency power to essential safety equipment without any restriction in power output.”

Selecting the right EN 50171 compliant Central Power Supply System

To ensure compliance, a CPS system should be selected, which is specifically designed for this purpose and is third-party certified by a globally recognised standard body.

With so many CPS system manufacturers claiming EN 50171 compliance, what does this really mean, and are all ‘EN 50171 compliant’ systems in the market really suitable for emergency lighting?

In our experience, there is a significant difference between ‘complies with’ products, which are self-certified by the manufacturer, and a truly qualified product which has been proven in the field for many years and has third-party certification for the intended application.

There are lots of systems available that claim to be ‘EN 50171 compliant’, when in reality they have been adapted or oversized to provide the same level of performance as a dedicated emergency lighting CPS system. As a result, due diligence is important when selecting these systems to ensure that the correct application and system integrity matches the unique conditions of the emergency lighting backup supply.

A compliant CPS system for your application

Selecting the right CPS starts with designing the whole installation carefully – from end to end. A critical part of any electrical installation (including emergency lighting) is ensuring the fault clearance, by operating circuit protective devices.

This is quite simple to design when you have thousands of amps of prospective fault current from the grid. However, in a mains-fail scenario, there is no grid and, as a result, the CPS system must rely solely on the fault current generation capacity of the CPS system.

For example, a typical 6A Type B final circuit-breaker shows that a minimum of 30A prospective fault current is required to clear this in 0.1 to 5 seconds.

There are EN 50171 compliant and even third party certified CPS systems available on the market today, which either won’t clear circuit-breaker or, are undersized for the application they will be used in for several reasons: the technology has been adapted from another application, the manufacturer is not responsible for ensuring this and mainly because the capacity to generate the prospective fault current in a mains-fail scenario has a large impact on the cost of the system.

The right advice

When selecting a CPS system for a project, consulting your specialist emergency lighting manufacturer on what size of final breaker the system can clear is very important. In line with industry guidance, manufacturers are required to declare this information, to allow an electrical installation to be designed safely, and to make sure it meets all applicable regulations, not just EN 50171.

For added safety, we would recommend that any critical life safety system should be further assessed against the requirement of IEC 61508 by a third party to truly prove and validate that the system will operate and perform reliably when required. IEC 61580 addresses the key safety activities for electrical, electronic and programmable electronic elements that are used for a safety function. The higher the Safety Integrity Level (SIL) the lower the probability of failure.


Managing an emergency lighting design and installation carries significant responsibilities. Ensuring that the CPS system is suitable for the project and will operate the whole installation safely lies solely with the electrical designer or the party selecting the CPS system.

When looking at value engineering projects, we would recommend a more pragmatic approach. Purely focusing on reducing costs and installing a lesser system that is not designed for the specific emergency lighting requirements, could ultimately put lives at risk. As such, making sure that your battery system is compliant and fit for purpose is not an option, it is a must!

The ABB EMEX CPS was developed solely as an emergency solution, fully compliant with EN50171 standards and 3rd party certified under Kitemark license KM 542294. Furthermore, it holds the Safety Integrity Level 2 (SIL2) Certification under Kitemark license KM673347, providing an ultimate life safety product with superior performance, sustainability and value throughout the project life cycle and has been applied successfully in all the markets that it has been tried in.


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