The term safety power supply refers to an electrical system designed to ensure the power supply of user equipment or parts of the system necessary for the safety of persons.

These systems also include emergency lighting systems which, designed to operate in the absence of ordinary lighting, ensure the possible of leaving buildings or places at risk by following the appropriate emergency signs.


The operation of these systems must be guaranteed regardless of whether there is a network or not. Safety regulations state that emergency power supply systems can be divided into two macro-categories: centralised systems and distributed systems.

Centralised emergency power supply systems provide power to all users of a system from a single point using a UPS in CPSS configuration.


A CPSS (Central Power Supply System) or backup UPS is a centralised power supply system, a UPS uninterruptible power supply with precise characteristics used to power emergency systems and, in particular, emergency lighting in buildings.




Emergency lighting systems are usually applied to:


  • Exit routes and associated safety signalling
  • Areas intended for electrical service, emergency generator units and main control panels of ordinary and safety power supply
  • Lift machinery areas
  • Air-conditioning units
  • Data processing centres
  • Kitchens
UPS per impianti di emergenza
UPS per impianti di sicurezza

Emergency power can, in any case, be provided for other safety equipment, such as:


  • automatic alarm detection and fire extinguishing systems
  • paging and calling systems
  • lifts designed to operate in the event of fire
  • extraction ventilation systems
  • safety and carbon monoxide signalling systems
  • miscellaneous electromedical equipment
  • Safety systems for particular buildings, e.g. in high-risk areas, safety curtains, etc.

A backup UPS must, to be used in emergency systems, meet the requirements of the European reference standard CEI/EN 50171 – Centralised systems for supplying safety services, in addition to the requirements of standard IEC EN 62040-3 Uninterruptible Power Supply Systems.





The CEI/EN 50171 standard establishes the characteristics and performance that a centralised UPS must have in order to be used as a power source for emergency lighting systems.

According to the standard, a CPSS UPS must meet specific requirements:

  • In accordance with EN 1838, the CPSS must be able to supply 120% of the prescribed charge, at least for the duration of the foreseen autonomy (nominal duration) and be able to start up a charge, previously switched off, with a response time of 0.5 seconds.
  • The inverter must be protected against reverse battery polarity.
  • The main entrance port and emergency line must be protected by circuit breakers.
  • The CPSS must not have external flammable components.
  • Following a discharge of the full expected range, the CPSS must be able to recharge its batteries to provide at least 80% of the original range within 12 hours of the start of charging.
  • The CPSS UPS must have long-life batteries with an expected life declared by the manufacturer of not less than 10 years, while sizing must provide a project end-of-life of 25%.
  • The batteries must, in accordance with EN 50272-2, be installed in rooms with a temperature lower than 25°C, and an automatic and manual test device must be provided for regular checking of battery conditions.
  • The CPS must adopt a system to protect the battery from complete discharge, an event which would lead to its irreparable damage.


In order to guarantee the feasibility of the checks required by law, the EN 50171 standard also stipulates that centralised power supply systems for emergency and safety must be equipped with operating and measuring devices. The standard also requires the presence of signalling via potential-free contacts relating to battery operation, end-of-range pre-alarm condition and the presence of generic alarm conditions also accompanied by an acoustic warning.


Because of its particular function, a security installation therefore requires an appropriate choice of CPSS system to be used in accordance with current European legislation.

The GTEC solution specifically designed for safety installations, in small- and medium-power applications, is the SHIELD CPS single-phase backup UPS.


SHIELD CPS, available in 5 different sizes (from 4.2 kVA up to 8.3 kVA), is equipped with state-of-the-art technology such as Power Factor 1 output and the ability to achieve 98% efficiency.

UPS soccorritore per impianti di sicurezza

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