oSIST prEN 2665-004:2026

• Abstract:

  This document specifies the characteristics of three-pole circuit breakers, temperature compensated with a rated current from 20 A to 50 A, used in aircraft on-board circuits at a temperature between −55 °C and 90 °C at an altitude of 15 000 m max.; These circuit breakers are operated by a push-pull type single pushbutton (actuator), with delayed action "trip-free" tripping; They will continue to function up to the short-circuit current.

• Status: Not Published
• Public Enquiry End Date: 30-Oct-2026
• ICS: 49.060 - Aerospace electric equipment and systems
• Technical Committee: I13 - Imaginarni 13
• Current Stage: 4020 - Public enquire (PE) (Adopted Project)
• Start Date: 04-Sep-2026
• Due Date: 22-Jan-2027
• Ref Project: prEN 2665-004 - Aerospace series - Circuit breakers, three-pole, temperature compensated, rated current 20 A to 50 A - Part 004: UNC thread terminals - Product standard

• Revises: SIST EN 2665-004:2014 - Aerospace series - Circuit breakers, three-pole, temperature compensated, rated current 20 A to 50 A - Part 004: UNC thread terminals - Product standard
• Effective Date: 08-Jan-2025

oSIST prEN 2665-004:2026 is a draft European Standard from CEN, prepared by ASD-STAN, for aerospace three-pole circuit breakers with UNC thread terminals. It specifies the characteristics, dimensions, electrical and mechanical performance, marking, and delivery codes for temperature compensated breakers rated from 20 A to 50 A for aircraft on-board circuits.

What does oSIST prEN 2665-004:2026 specify?

oSIST prEN 2665-004:2026 specifies three-pole, temperature compensated circuit breakers for aircraft on-board circuits used between -55 °C and 90 °C and up to 15 000 m altitude. These breakers use a push-pull type single pushbutton actuator, delayed-action trip-free tripping, and are intended to keep functioning up to short-circuit current.

The document is organized into:

• Clause 1 - Scope
• Clause 2 - Normative references
• Clause 3 - Terms and definitions
• Clause 4 - Dimensions and mass
• Clause 5 - Characteristics
• Clause 6 - Designation
• Clause 7 - Rated current code
• Clause 8 - Delivery codes
• Clause 9 - Marking
• Clause 10 - Technical specification

In practice, the standard gives the product definition, the installation interface, the electrical behavior, and the identification rules needed to specify, buy, test, and install the breaker consistently.

What are the key requirements of oSIST prEN 2665-004:2026?

oSIST prEN 2665-004:2026 combines dimensional control, mechanical robustness, environmental endurance, and electrical trip performance. For a user, that means the breaker is not only sized to fit, but also qualified for the intended aircraft conditions and protection duty.

Dimensions and installation

Clause 4.1 requires the configuration, dimensions, and tolerances shown in Figure 1, with dimensions in millimetres except for the 8-32 UNC terminal thread. The illustration is not the only acceptable shape, but the stated dimensions are binding, which matters when checking interchangeability and panel fit.

Clause 4.2 defines the electrical state: pushbutton released means CB open, and pushbutton pressed means CB closed. The load and supply can be inverted, which simplifies wiring practice.

Clause 4.3 limits mass to 180 g maximum for delivery code A including hardware, and Clause 4.4 requires panel mounting to follow EN 2665-001. This helps buyers and installers control weight and confirm that the mounting matches the approved family.

Mechanical and environmental characteristics

Clause 5.2 requires fasteners to comply with EN 6113 and gives installation torque values for the attaching nut and connection hardware. It also includes vibration, shock, and mechanical endurance requirements, so qualification testing covers both handling loads and in-service service life.

Clause 5.3 covers humidity, corrosion, contaminating liquids, and lightning-caused overvoltage by reference to EN 2665-001. These items matter because aircraft equipment must keep operating after exposure to moisture, contaminants, and electrical stress.

Electrical performance

Clause 5.4.1 sets the operating circuit voltage range at 115 V to 200 V AC, 360 Hz to 800 Hz, three phases. Clause 5.4.2 limits voltage drop at rated current, so the breaker’s internal losses stay under control.

Clauses 5.4.3 and 5.4.4 define the minimum and maximum tripping thresholds and overload trip times at different temperatures and altitude conditions. This tells a designer or test lab how quickly the breaker must respond under normal overloads.

Clause 5.4.5 defines short-circuit performance, including the prospective currents, altitude conditions, and the CO and OCO operating sequence from EN 3841-305. Clause 5.4.6 then sets no-load and load endurance, Clause 5.4.7 covers dielectric rigidity, and Clause 5.4.8 covers insulation resistance. Together, these clauses show whether the breaker can interrupt faults, survive repeated operation, and retain electrical isolation.

Identification and supply

Clauses 6 to 9 define designation, rated current code, delivery codes, and marking. This is the part that supports ordering, traceability, and correct assembly of the breaker and its hardware.

What terms does oSIST prEN 2665-004:2026 define?

• Trip-free - A tripping action that opens the circuit breaker even if the actuator is held in the operated position.
• Actuator - The push-pull type single pushbutton used to operate the circuit breaker.
• CB - Circuit breaker, the device identified in Figure 2 as open or closed.
• Rated current - The current rating used throughout the document for classification, marking, and performance checks.
• Load - The circuit side shown in Figure 2 that receives power through the breaker.
• Supply - The power source side shown in Figure 2; the document allows the load and supply to be inverted.
• CO and OCO - The short-circuit test operation sequence used with EN 3841-305, meaning break and make-break operations.

Who uses oSIST prEN 2665-004:2026?

Aircraft electrical engineers use oSIST prEN 2665-004:2026 when selecting a breaker for a circuit that must work within the stated voltage, temperature, and altitude limits. Test laboratories use it to verify tripping, short-circuit behavior, endurance, dielectric rigidity, and insulation resistance.

Manufacturers use it to design the breaker body, actuator, terminals, mounting arrangement, and hardware. Quality managers and buyers use it to check part marking, delivery codes, and the hardware kit arrangement before release or purchase.

Installers and maintenance teams use it for panel mounting, tightening torque, and identification on the product and packaging.

What changed in oSIST prEN 2665-004:2026 from the previous edition?

oSIST prEN 2665-004:2026 will supersede EN 2665-004:2013. The foreword lists these technical changes:

• revised short-circuit values in Table 5
• mass changed from 162 g to 180 g in 4.3
• modified external diameter of the button in Figure 1

Which standards are used with oSIST prEN 2665-004:2026?

• EN 2350 - supplies the terms and definitions used in Clause 3.
• EN 2665-001 - provides panel mounting, material and surface treatment, environmental characteristics, insulation resistance, and the technical specification.
• EN 3841-305 - provides the short-circuit test method and the meaning of CO and OCO.
• EN 6113 - specifies the connecting and attachment hardware used with the breaker.
• SAE-AMS-STD-595 - provides the colour references used for the black and white markings in Figure 1.
• TR 6083 - is cited with the panel cut-out positioning shown in Figure 1.

What does the oSIST prEN 2665-004:2026 document contain?

oSIST prEN 2665-004:2026 contains two main figures and nine tables that drive design and verification. Figure 1 gives the configuration, dimensions, tolerances, terminal thread, actuator, and panel-mounting features; Figure 2 gives the electrical diagram and the open/closed states.

The tables cover nominal voltage, voltage drop, tripping thresholds, overload trip time, short-circuit values, endurance, dielectric rigidity, rated current code, and delivery codes. That makes the document useful both for product design and for acceptance testing.

SLOVENSKI STANDARD
01-oktober-2026
Aeronavtika - Odklopniki, tripolni, temperaturno kompenzirani, za naznačene
tokove od 20 A do 50 A - 004. del: UNC-navojni priključki - Standard za proizvod
Aerospace series - Circuit breakers, three-pole, temperature compensated, rated current
20 A to 50 A - Part 004: UNC thread terminals - Product standard
Luft- und Raumfahrt - Schutzschalter, dreipolig, temperaturkompensiert, Nennströme
von 20 A bis 50 A - Teil 004: UNC-Klemmengewinde - Produktnorm
Série aérospatiale - Disjoncteurs tripolaires compensés en température, intensités
nominales 20 A à 50 A - Partie 004 : Bornes à filetage UNC - Norme de produit
Ta slovenski standard je istoveten z: prEN 2665-004
ICS:
49.060 Letalska in vesoljska Aerospace electric
električna oprema in sistemi equipment and systems
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

DRAFT
EUROPEAN STANDARD
NORME EUROPÉENNE
EUROPÄISCHE NORM
August 2026
ICS 49.060 Will supersede EN 2665-004:2013
English Version
Aerospace series - Circuit breakers, three-pole,
temperature compensated, rated current 20 A to 50 A -
Part 004: UNC thread terminals - Product standard
Série aérospatiale - Disjoncteurs tripolaires compensés Luft- und Raumfahrt - Schutzschalter, dreipolig,
en température, intensités nominales 20 A à 50 A - temperaturkompensiert, Nennströme von 20 A bis 50
Partie 004 : Bornes à filetage UNC - Norme de produit A - Teil 004: UNC-Klemmengewinde - Produktnorm
This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee ASD-
STAN.
If this draft becomes a European Standard, CEN members are bound to comply with the CEN/CENELEC Internal Regulations
which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.

This draft European Standard was established by CEN in three official versions (English, French, German). A version in any other
language made by translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC
Management Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are
aware and to provide supporting documentation.

Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without
notice and shall not be referred to as a European Standard.

EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2026 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 2665-004:2026 E
worldwide for CEN national Members.

Contents Page
European foreword . 3
1 Scope . 4
2 Normative references . 4
3 Terms and definitions . 4
4 Dimensions and mass . 4
4.1 Dimensional characteristics . 4
4.2 Electrical diagram . 6
4.3 Mass . 6
4.4 Panel mounting . 6
5 Characteristics . 6
5.1 Material, surface treatment . 6
5.2 Mechanical characteristics . 6
5.2.1 Fasteners . 6
5.2.2 Recommended tightening torque of attaching nut for installation . 6
5.2.3 Recommended tightening torque of connection hardware for installation . 6
5.2.4 Resistance to vibrations . 7
5.2.5 Resistance to shocks . 7
5.2.6 Mechanical endurance . 7
5.3 Environment characteristics . 7
5.3.1 Humidity . 7
5.3.2 Corrosion . 7
5.3.3 Contaminating liquids . 7
5.3.4 Overvoltage caused by lightning . 7
5.4 Electrical characteristics . 7
5.4.1 Nominal voltage of operational circuits . 7
5.4.2 Voltage drop at Ι . 7
n
5.4.3 Minimum and maximum tripping thresholds . 8
5.4.4 Overload trip . 8
5.4.5 Short-circuit values . 8
5.4.6 No-load and load endurance . 9
5.4.7 Dielectric rigidity . 9
5.4.8 Insulation resistance . 10
6 Designation . 10
7 Rated current code . 10
8 Delivery codes . 10
9 Marking . 11
10 Technical specification . 11
Bibliography . 12

European foreword
This document (prEN 2665-004:2026) has been prepared by ASD-STAN.
After enquiries and votes carried out in accordance with the rules of this Association, this document has
received the approval of the National Associations and the Official Services of the member countries of
ASD-STAN, prior to its presentation to CEN.
This document is currently submitted to the CEN Enquiry.
This document will supersede EN 2665-004:2013.
...