EN 50171:2021/prA1:2026
(Amendment)Central safety power supply systems
- Abstract
This document specifies the general requirements for central power supply systems for an independent energy supply to essential safety equipment. This standard covers systems that are permanently connected to AC supply voltages not exceeding 1 000 V and use batteries as an alternative power source. Central safety power supply systems are intended to ensure energy supply to emergency escape lighting in the event of normal supply failure and may be suitable for energizing other essential safety equipment, for example: – electric circuits of automatic fire extinguishing installations; – paging systems and signalling safety installations; – smoke extraction equipment; – carbon monoxide warning systems; – special safety installations related to specific buildings, e.g. high-risk areas. The power supply of CPS systems should be dedicated only to the essential safety equipment, and not for other type of loads such as general purpose IT or industrial systems etc. Combinations of the aforementioned safety equipment types are permitted together on the same central safety power supply system providing the availability for safety equipment loads is not impaired. A fault occurring in a circuit should not cause the interruption in any other circuit used to supply essential safety equipment. Schematic representations of typical central safety power supply equipment are depicted in Clause 4. Power supply systems for fire alarm equipment that are covered by EN 54 (series) are excluded.
- Status
- Not Published
- Publication Date
- 04-Mar-2027
- Technical Committee
- CLC/TC 22X - Power electronics
- Drafting Committee
- CLC/TC 22X/WG 07 - Power supplies
- Current Stage
- 4060 - Enquiry results established and sent to TC, SR, BTTF - Enquiry
- Start Date
- 16-Oct-2026
- Due Date
- 03-Feb-2026
- Completion Date
- 16-Oct-2026
EN 50171:2021/prA1:2026 is a CENELEC project amendment to EN 50171:2021 on central safety power supply systems. It applies to systems permanently connected to AC supply voltages not exceeding 1 000 V and using batteries as the alternative power source. The document updates the rules for supplying emergency escape lighting and other essential safety equipment, and aligns the standard with revised EMC and UPS references.
What does EN 50171:2021/prA1:2026 specify?
EN 50171:2021/prA1:2026 specifies amendments to the European Standard for central safety power supply systems, including their scope, definitions, operating modes, EMC requirements, battery protection, monitoring and battery life provisions. It is organized as a foreword and 24 modification items that revise Clauses 1, 2, 3, 4.2 to 4.7, 5.1, 5.2, and 6.1 to 6.13.4.
The standard applies to systems used for independent energy supply to essential safety equipment, especially emergency escape lighting. It also allows the same CPS to feed other essential safety loads, such as fire extinguishing circuits, paging and signalling safety installations, smoke extraction equipment, carbon monoxide warning systems, and special safety installations for specific buildings.
It excludes power supply systems for fire alarm equipment covered by the EN 54 series. In practice, that helps users avoid applying the wrong standard to fire alarm power supplies.
What are the key requirements of EN 50171:2021/prA1:2026?
EN 50171:2021/prA1:2026 mainly clarifies how a CPS must behave in emergency service, how it must be monitored, and which EMC and UPS requirements apply.
Operating modes and continuity of supply
Clause 4 revises the graphics for the different operating modes, including changeover mode, mode without interruption, and their variants with additional control switching devices. These figures matter because they show how the load is transferred and what kind of switching arrangement is acceptable.
Clause 6.1 adds that, in battery mode, the CPS shall maintain continuity of supply to emergency lighting even if a first insulation failure occurs in the battery circuit or luminaire circuit. In practice, this means the system must keep emergency lighting alive through a single insulation fault.
EMC and location-dependent requirements
Clause 5.1 replaces the battery protection item and adds detailed EMC obligations. The CPS shall protect the battery against deep discharge, and its immunity and emissions shall follow the applicable EN IEC EMC standards for the installation location.
For systems using a UPS to feed the essential safety system, EN IEC 62040-2 applies as specified for residential, commercial and light-industrial, and industrial locations. The location categories matter because they determine which EMC limits and categories the system must meet.
Battery, monitoring and readiness
Clause 5.2 now requires the user to specify the type and intended location of the battery. Clause 6.8.1 adds battery charge/discharge current to the list of monitored values, and Clause 6.8.2 clarifies when the system is ready to operate.
Clause 6.12.1 adds requirements for automatic test units with recording facility, including constant charge monitoring or periodic monitoring at intervals shorter than 5 min. This helps users and maintainers verify system status without relying only on manual checks.
UPS use and battery life
Clauses 6.3.1 and 6.6.11 state that when a CPS uses a UPS, it shall comply with EN IEC 62040-1 and the additional requirements of this document. Clause 6.13.2 sets a design life expectancy of at least 10 years at 20 °C for batteries used in CPS and LPS. For buyers and maintainers, that affects battery selection, service planning and replacement intervals.
What terms does EN 50171:2021/prA1:2026 define?
- CPS - Central safety power supply system; the central power source for essential safety loads.
- LPS - Low power safety supply system; the document applies the same 10-year battery life expectation here.
- UPS - Uninterruptible power system; when used in a CPS, it must also meet EN IEC 62040-1 and EN IEC 62040-2 as relevant.
- EMC - Electromagnetic compatibility; the ability of the system to operate without causing or suffering unacceptable interference.
- Residential location - A domestic setting connected directly to the low-voltage public mains network.
- Commercial location and light-industrial location - A non-residential setting on the low-voltage network, with examples such as retail, offices, hospitals and workshops.
- Industrial location - A location with a separate power network, typically supplied from a high- or medium-voltage transformer for the installation.
Who uses EN 50171:2021/prA1:2026?
EN 50171:2021/prA1:2026 is used by manufacturers, designers, installers, test laboratories and specifiers of central safety power supply systems. It is relevant to emergency lighting, building safety systems, fire protection equipment, smoke extraction, paging, signalling and other essential safety loads. Buyers and quality managers use it to check whether a CPS is suited to the intended location, battery arrangement and EMC environment.
What changed in EN 50171:2021/prA1:2026 from the previous edition?
Compared with EN 50171:2021, EN 50171:2021/prA1:2026 updates the scope wording, replaces and adds several normative references, and adds three EMC-related location definitions. It also revises the operating-mode figures in Clause 4.
The amendment adds or clarifies requirements for deep discharge protection, EMC compliance by location, UPS use, battery monitoring, automatic test units, and 10-year battery life expectations. It also changes several wording points, including the emergency activation timing and the test conditions in Clause 6.
Which standards are used with EN 50171:2021/prA1:2026?
- EN IEC 62040-1 - provides UPS safety requirements when a CPS uses a UPS.
- EN IEC 62040-2 - provides EMC requirements for UPS used in essential safety supply.
- EN IEC 61000-6-2 - provides immunity requirements for industrial environments.
- EN IEC 61000-6-3 - provides emission requirements for residential locations.
- EN IEC 61000-6-4 - provides emission requirements for industrial environments.
- EN IEC 61000-6-8:2020 - provides emission requirements for professional equipment in commercial and light-industrial locations.
- EN 54 series - identifies fire alarm equipment that is outside the scope of this standard.
What does the EN 50171:2021/prA1:2026 document contain?
EN 50171:2021/prA1:2026 contains replacement figures for the main CPS operating modes in Clause 4, including changeover and no-interruption arrangements. It also contains edited wording across Clauses 5 and 6 for EMC, user-specified battery data, insulation failure behavior, charging and rectifier use, and deep discharge protection.
The text gives the points a designer or assessor needs to check during design review and compliance verification: what must be monitored, what battery and UPS characteristics apply, and how readiness and emergency behavior are judged.
Relations
- Effective Date
- 15-Oct-2024
- Effective Date
- 15-Oct-2024
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Frequently Asked Questions
EN 50171:2021/prA1:2026 is a draft published by CLC. Its full title is "Central safety power supply systems". This standard covers: This document specifies the general requirements for central power supply systems for an independent energy supply to essential safety equipment. This standard covers systems that are permanently connected to AC supply voltages not exceeding 1 000 V and use batteries as an alternative power source. Central safety power supply systems are intended to ensure energy supply to emergency escape lighting in the event of normal supply failure and may be suitable for energizing other essential safety equipment, for example: – electric circuits of automatic fire extinguishing installations; – paging systems and signalling safety installations; – smoke extraction equipment; – carbon monoxide warning systems; – special safety installations related to specific buildings, e.g. high-risk areas. The power supply of CPS systems should be dedicated only to the essential safety equipment, and not for other type of loads such as general purpose IT or industrial systems etc. Combinations of the aforementioned safety equipment types are permitted together on the same central safety power supply system providing the availability for safety equipment loads is not impaired. A fault occurring in a circuit should not cause the interruption in any other circuit used to supply essential safety equipment. Schematic representations of typical central safety power supply equipment are depicted in Clause 4. Power supply systems for fire alarm equipment that are covered by EN 54 (series) are excluded.
This document specifies the general requirements for central power supply systems for an independent energy supply to essential safety equipment. This standard covers systems that are permanently connected to AC supply voltages not exceeding 1 000 V and use batteries as an alternative power source. Central safety power supply systems are intended to ensure energy supply to emergency escape lighting in the event of normal supply failure and may be suitable for energizing other essential safety equipment, for example: – electric circuits of automatic fire extinguishing installations; – paging systems and signalling safety installations; – smoke extraction equipment; – carbon monoxide warning systems; – special safety installations related to specific buildings, e.g. high-risk areas. The power supply of CPS systems should be dedicated only to the essential safety equipment, and not for other type of loads such as general purpose IT or industrial systems etc. Combinations of the aforementioned safety equipment types are permitted together on the same central safety power supply system providing the availability for safety equipment loads is not impaired. A fault occurring in a circuit should not cause the interruption in any other circuit used to supply essential safety equipment. Schematic representations of typical central safety power supply equipment are depicted in Clause 4. Power supply systems for fire alarm equipment that are covered by EN 54 (series) are excluded.
EN 50171:2021/prA1:2026 is classified under the following ICS (International Classification for Standards) categories: 29.240 - Power transmission and distribution networks. The ICS classification helps identify the subject area and facilitates finding related standards.
EN 50171:2021/prA1:2026 has the following relationships with other standards: It is inter standard links to EN 50171:2021, EN 50171:2021/AC:2024-08. Understanding these relationships helps ensure you are using the most current and applicable version of the standard.
EN 50171:2021/prA1:2026 is associated with the following European legislation: EU Directives/Regulations: 2014/30/EU, 2014/35/EU; Standardization Mandates: M/511, M/552. When a standard is cited in the Official Journal of the European Union, products manufactured in conformity with it benefit from a presumption of conformity with the essential requirements of the corresponding EU directive or regulation.
EN 50171:2021/prA1:2026 is available in PDF format for immediate download after purchase. The document can be added to your cart and obtained through the secure checkout process. Digital delivery ensures instant access to the complete standard document.
Standards Content (Sample)
SLOVENSKI STANDARD
01-julij-2026
Centralni varnostni napajalni sistemi
Central safety power supply systems
Zentrale Sicherheitsstromversorgungssysteme
Systèmes d'alimentation de sécurité à source centrale
Ta slovenski standard je istoveten z: EN 50171:2021/prA1:2026
ICS:
29.200 Usmerniki. Pretvorniki. Rectifiers. Convertors.
Stabilizirano električno Stabilized power supply
napajanje
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
NORME EUROPÉENNE PROJET
EN 50171:2021
EUROPÄISCHE NORM
EUROPEAN STANDARD
prA1
Juillet 2026
ICS 29.240 -
Version française
Systèmes d'alimentation de sécurité à source centrale
Zentrale Sicherheitsstromversorgungssysteme Central safety power supply systems
Ce projet d'amendement prA1, s'il est approuvé, modifiera la Norme Européenne EN 50171:2021; il est soumis aux membres du CENELEC
pour enquête.
Date limite du CENELEC: 2026-10-16.
Il a été établi par le CLC/TC 22X.
Si ce projet devient un amendement, les membres du CENELEC sont tenus de se soumettre au Règlement Intérieur du CEN/CENELEC,
qui définit les conditions dans lesquelles doit être attribué, sans modification, le statut de norme nationale à cet amendement.
Le présent projet d'amendement a été établi par le CENELEC en trois versions officielles (allemand, anglais, français).
Une version dans une autre langue faite par traduction sous la responsabilité d'un membre du CENELEC dans sa langue nationale, et
notifiée au CEN-CENELEC Management Centre, a le même statut que les versions officielles.
Les membres du CENELEC sont les comités électrotechniques nationaux des pays suivants: Allemagne, Autriche, Belgique, Bulgarie,
Chypre, Croatie, Danemark, Espagne, Estonie, Finlande, France, Grèce, Hongrie, Irlande, Islande, Italie, Lettonie, Lituanie, Luxembourg,
Malte, Norvège, Pays-Bas, Pologne, Portugal, République de Macédoine du Nord, République de Serbie, République Tchèque, Roumanie,
Royaume-Uni, Slovaquie, Slovénie, Suède, Suisse et Turquie.
Les destinataires du présent projet sont invités à présenter, avec leurs observations, notifications des droits de propriété dont ils auraient
éventuellement connaissance et à fournir une documentation explicative.
Avertissement: Le présent document n'est pas une Norme Européenne. Il est diffusé pour examen et observations. Il est susceptible de
modification sans préavis et ne doit pas être cité comme Norme Européenne.
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
European Committee for Electrotechnical Standardization
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Bruxelles
© 2026 CENELEC Tous droits d'exploitation sous quelque forme et de quelque manière que ce soit réservés dans le monde entier aux
membres du CENELEC.
Project: 80778 Réf. n° EN 50171:2021/prA1:2026 F
Contents Page
1 European foreword . 3
2 1 Modification to Clause 1, “Scope” . 4
3 2 Modification to Clause 2, “Normative references” . 4
4 3 Modification to Clause 3, “Terms and definitions” . 4
5 4 Modification to 4.2, “Changeover mode” . 5
6 5 Modification to 4.3, “Mode without interruption” . 6
7 6 Modification to 4.4, “Changeover mode with an additional control switching device for
8 central switching of the load” . 6
9 7 Modification to 4.5, “Changeover mode with an additional control switching device for
10 partial switching of the load “ . 6
11 8 Modification to 4.6, “Non-maintained changeover mode” . 7
12 9 Modification to 4.7, “Mode without interruption with an additional control switching device
13 for central switching of the load” . 7
14 10 Modification to 5.1, “Normal operating conditions and requirements for central safety
15 power supply systems” . 7
16 11 Modification to 5.2, “Requirements to be specified by the user” . 8
17 12 Modification to 6.1, “General requirements” . 8
18 13 Modification to 6.3.1, “Battery charges and rectifiers” . 8
19 14 Modification to 6.5.4 . 8
20 15 Modification to 6.6.8 . 8
21 16 Modification to 6.6.11 . 8
22 17 Modification to 6.7 “Deep discharge protection” . 8
23 18 Modification to 6.8.1 . 9
24 19 Modification to 6.8.2 . 9
25 20 Modification to 6.8.4 . 9
26 21 Modification to 6.12.1 . 9
27 22 Modification to 6.12.4 . 9
28 23 Modification to 6.13.2 . 9
29 24 Modification to 6.13.4 . 9
30 European foreword
31 This document (EN 50171:2021/prA1:2026) has been prepared by CLC/TC 22X “Power electronics”.
32 This document is currently submitted to the Enquiry.
33 The following dates are proposed:
• latest date by which the existence of this (doa) dav + 6 months
document has to be announced at national level
• latest date by which this document has to be (dop) dav + 12 months
implemented at national level by publication of
an identical national standard or by
endorsement
• latest date by which the national standards (dow) dav + 36 months
conflicting with this document have to be (to be confirmed or
withdrawn modified when voting)
35 1 Modification to Clause 1, “Scope”
nd
36 In the 4th paragraph, 2 sentence, replace “the interruption” with “a failure”.
37 2 Modification to Clause 2, “Normative references”
38 Replace the references to EN 62040-1, EN 61000-6-2, EN 61000-6-3 and EN 61000-6-4 with the following,
39 respectively:
40 EN IEC 62040-1, Uninterruptible power systems (UPS) - Part 1: Safety requirements (IEC 62040-1)
41 EN IEC 61000-6-2, Electromagnetic compatibility (EMC) - Part 6-2: Generic standards - Immunity standard for
42 industrial environments (IEC 61000-6-2)
43 EN IEC 61000-6-3, Electromagnetic compatibility (EMC) - Part 6-3: Generic standards - Emission standard for
44 equipment in residential locations (IEC 61000-6-3)
45 EN IEC 61000-6-4, Electromagnetic compatibility (EMC) - Part 6-4: Generic standards - Emission standard for
46 industrial environments (IEC 61000-6-4)
47 Add the following references:
48 EN IEC 61000-6-8:2020, Electromagnetic compatibility (EMC) - Part 6-8: Generic standards - Emission
49 standard for professional equipment in commercial and light-industrial locations
50 EN IEC 62040-2, Uninterruptible power systems (UPS) - Part 2: Electromagnetic compatibility (EMC)
51 requirements
52 3 Modification to Clause 3, “Terms and definitions”
53 Add the 3 following definitions:
54 3.24
55 residential location
56 area of land designated for domestic dwellings where the mains pow
...