What a central power system is
A central power system (CPS) is a static inverter that supplies emergency lighting and life-safety circuits from a centralised battery bank when the mains fails. Instead of dozens of individual battery luminaires, a CPS feeds the whole emergency lighting network from one maintained, testable source — simplifying compliance, maintenance and monitoring.
BS EN 50171 explained
BS EN 50171 is the European standard for central power supply systems for emergency lighting. It defines the performance, autonomy, monitoring and construction requirements a CPS must meet so that life-safety lighting is guaranteed to operate when needed. Legrand's central power supplies are designed to EN 50171, making them suitable for healthcare, commercial and public buildings where compliance is mandatory.
CPS vs a standard UPS
A CPS and a UPS share the same inverter-and-battery principle, but they are built for different jobs. A UPS protects IT and critical loads for minutes; a CPS is engineered for life-safety lighting for 1–3 hours, with battery monitoring, automatic periodic testing and compliance documentation built in. A CPS is also rated for the long-duration discharge and ambient conditions of an emergency installation, where a standard UPS is not.
Where CPS are used and how to size
CPS suit hospitals, care homes, offices, retail, transport hubs and any building where emergency lighting must meet building regulations and fire-safety standards. Size the CPS to the total emergency lighting load (kW) and the required autonomy — typically 1, 2 or 3 hours — then coordinate it with the building's UPS and standby generator so life-safety circuits stay powered through any event. See our Legrand range for EN 50171 central power supplies.
Frequently asked questions
What is a central power system (CPS)?
A static inverter with a centralised battery bank that supplies emergency lighting and life-safety circuits when the mains fails, replacing individual battery luminaires.
What is BS EN 50171?
The European standard defining performance, autonomy, monitoring and construction requirements for central power supply systems for emergency lighting.
Is a CPS the same as a UPS?
No. A UPS protects IT loads for minutes; a CPS is engineered for life-safety lighting for 1–3 hours, with automatic testing and compliance documentation built in.
How long must emergency lighting last?
Typically 1–3 hours of autonomy, depending on building type and fire-safety regulations. The CPS battery bank is sized to deliver this at full emergency load.