SIST EN 3841-404:2005

• Abstract:

  This standard specifies a method of verifying explosion proofness of circuit breakers.; It shall be used together with EN 3841-100.

• Status: Published
• Publication Date: 31-Mar-2005
• ICS: 49.060 - Aerospace electric equipment and systems
• Technical Committee: SS SPL - Technical Board for the general field
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 01-Apr-2005
• Due Date: 01-Apr-2005
• Completion Date: 01-Apr-2005
• Ref Project: EN 3841-404:2004 - Aerospace series - Circuit breakers - Test methods - Part 404: Explosion proofness

• Refers: SIST EN 3841-100:2024 - Aerospace series - Circuit breakers - Test methods - Part 100: General
• Effective Date: 28-Jan-2026
• Refers: SIST EN 14893:2007 - LPG equipment and accessories - Transportable Liquefied Petroleum Gas (LPG) welded steel pressure drums with a capacity between 150 litres and 1 000 litres
• Effective Date: 28-Jan-2026
• Referred By: SIST EN 2995-001:2024 - Aerospace series - Circuit breakers, single-pole, temperature compensated, rated currents 1 A to 25 A - Part 001: Technical specification
• Effective Date: 28-Jan-2026
• Referred By: SIST EN 4839-001:2018 - Aerospace series - Arc fault circuit breakers, three-poles, temperature compensated, rated current 3 A to 25 A - 115 V a.c. 400 Hz constant frequency - Part 001: Technical specification
• Effective Date: 28-Jan-2026
• Referred By: SIST EN 3774-001:2015 - Aerospace series - Circuit breakers, three-pole, temperature compensated, rated currents 1 A to 25 A - Part 001: Technical specification
• Effective Date: 28-Jan-2026
• Referred By: SIST EN 3661-001:2025 - Aerospace series - Circuit breakers, single-pole, temperature compensated, rated currents 20 A to 50 A - Part 001: Technical specification
• Effective Date: 28-Jan-2026
• Referred By: SIST EN 3773-001:2025 - Aerospace series - Circuit breakers, single-pole, temperature compensated, rated currents 1 A to 25 A - Part 001: Technical specification
• Effective Date: 28-Jan-2026
• Referred By: SIST EN 4838-001:2018 - Aerospace series - Arc Fault Circuit breakers, single-pole, temperature compensated, rated current 3 A to 25 A - 115 V a.c. 400 Hz Constant Frequency - Part 001: Technical specification
• Effective Date: 28-Jan-2026
• Referred By: SIST EN 2665-001:2014 - Aerospace series - Circuit breakers, three-pole, temperature compensated, rated current 20 A to 50 A - Part 001: Technical specification
• Effective Date: 28-Jan-2026
• Referred By: SIST EN 2794-001:2014 - Aerospace series - Circuit breakers, single-pole, temperature compensated, rated current 20 A to 50 A - Part 001: Technical specification
• Effective Date: 28-Jan-2026
• Referred By: SIST EN 2996-001:2024 - Aerospace series - Circuit breakers, three-pole, temperature compensated, rated currents 1 A to 25 A - Part 001: Technical specification
• Effective Date: 28-Jan-2026
• Referred By: SIST EN 2794-001:2024 - Aerospace series - Circuit breakers, single-pole, temperature compensated, rated currents 20 A to 50 A - Part 001: Technical specification
• Effective Date: 28-Jan-2026
• Referred By: SIST EN 2665-001:2024 - Aerospace series - Circuit breakers, three-pole, temperature compensated, rated currents 20 A to 50 A - Part 001: Technical specification
• Effective Date: 28-Jan-2026

SIST EN 3841-404:2005 is the Slovenian adoption of EN 3841-404:2004, published by SIST for the aerospace sector. It specifies a test method for verifying the explosion proofness of circuit breakers, and it is intended to be used together with EN 3841-100. In practice, it tells test laboratories and aerospace manufacturers how to set up the chamber, test mixture, temperature and operating sequence for this verification.

What does SIST EN 3841-404:2005 specify?

SIST EN 3841-404:2005 specifies a method for checking whether a circuit breaker is explosion proof under test conditions. The document is structured as a short test method: Clause 1 gives the scope, Clause 2 lists the normative references, and Clause 3 sets out the mounting, procedure and acceptance requirement.

Clause 3 is the technical core. It separates the test into how the specimen is mounted, how the test is run, and what result is acceptable. That structure matters because users need to build the right test setup before they can judge the result.

What are the key requirements of SIST EN 3841-404:2005?

SIST EN 3841-404:2005 requires the circuit breaker to be tested in a chamber that can expose it evenly to an explosive mixture. The chamber must be large enough for uniform exposure, mounted with the specimen near the centre, and equipped so the breaker can be operated with the chamber closed. In practice, this means the lab must control both the physical arrangement and the operating access before the test starts.

• Clause 3.1.1 - test mounting: the chamber needs a spark plug to verify combustibility after the operations, and a way to switch the circuit breakers on while closed. This lets the operator confirm the mixture and run the test safely.
• Clause 3.1.2 - test circuit: the document gives separate circuit arrangements for d.c. and a.c. single-pole testing, and for a.c. three-pole testing. The reader must select the circuit that matches the breaker configuration.
• Clause 3.1.3 - test mixture: the mixture is air and fuel vapour, using 100/130 octane gasoline, propane or standard hexane at a volumetric ratio of 13:1, following ISO 7137. This matters because the ignition risk depends on using the specified mixture.
• Clause 3.1.4 and 3.1.5 - test conditions: the test temperature is 70 °C and the chamber pressure is atmospheric pressure at normal altitude. These conditions define the environment in which the breaker is challenged.
• Clause 3.2 - procedure: the chamber is heated, filled with the explosive mixture, and the circuit breakers are stored in that atmosphere for 3 h before break operations. The operations are carried out at 1 h intervals, and the mixture must remain explosive during the period.
• Clause 3.3 - requirement: the mixture shall not ignite when the circuit breakers are operated. After the operations, the combustibility of the mixture is checked with the spark plug, and if the mixture does not ignite, the test is repeated with new test samples. This gives a clear pass/fail criterion and a retest rule.

What terms does SIST EN 3841-404:2005 define?

SIST EN 3841-404:2005 uses several technical terms and abbreviations that are important for reading the method.

• Explosion proofness - the ability of a circuit breaker to be operated without igniting the explosive mixture used in the test.
• Circuit breaker - the test specimen being mounted and operated in the chamber.
• Test chamber - the enclosed volume where the breaker is exposed to the explosive atmosphere.
• Test mixture - the air and fuel vapour mixture used to create the explosive atmosphere for the verification.
• d.c. - direct current, used in one of the test circuit arrangements.
• a.c. - alternating current, used in the single-pole and three-pole circuit arrangements.
• Spark plug - the device used after the test to verify whether the mixture is still combustible.

Who uses SIST EN 3841-404:2005?

SIST EN 3841-404:2005 is used by aerospace manufacturers, test laboratories, and quality teams that need to verify circuit breaker performance in explosive atmospheres. It is also relevant to buyers and approval engineers who specify test evidence for aerospace electrical equipment.

In practice, users apply it when setting up qualification or verification tests, selecting the right test circuit, preparing the explosive mixture, and documenting whether the breaker caused ignition.

What changed in SIST EN 3841-404:2005 from the previous edition?

SIST EN 3841-404:2005 is the Slovenian adoption of EN 3841-404:2004.

Which standards are used with SIST EN 3841-404:2005?

• EN 3841-100 - provides the general circuit breaker test method framework that this part must be used with, including the broader test setup and product-standard connection.
• ISO 7137 - provides the aircraft environmental conditions and test procedures referenced for the explosive mixture and test context.

What does the SIST EN 3841-404:2005 document contain?

The document contains a foreword, a scope, normative references, and Clause 3 with the test method. Clause 3 includes the mounting requirements, two circuit diagrams in Figure 1 and Figure 2, the fuel-air mixture description, temperature and pressure conditions, the test sequence, and the pass/fail requirement.

For a test engineer, the most useful parts are the circuit diagrams and the step-by-step procedure, because they show how to build the test and when to check for ignition. For a buyer or approver, the document provides a clear, narrow method for demonstrating explosion proofness of circuit breakers under defined conditions.

SLOVENSKI STANDARD
01-april-2005
Aeronavtika - Odklopniki - 404. del: Eksplozijska tesnost
Aerospace series - Circuit breakers - Test methods - Part 404: Explosion proofness
Luft- und Raumfahrt - Schutzschalter - Prüfverfahren - Teil 404: Explosionsdichtheit
Série aérospatiale - Disjoncteurs - Méthodes d'essais - Partie 404 : Antidéflagration
Ta slovenski standard je istoveten z: EN 3841-404:2004
ICS:
49.060 /HWDOVNDLQYHVROMVND Aerospace electric
HOHNWULþQDRSUHPDLQVLVWHPL equipment and systems
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN 3841-404
NORME EUROPÉENNE
EUROPÄISCHE NORM
December 2004
ICS 49.060
English version
Aerospace series - Circuit breakers - Test methods - Part 404:
Explosion proofness
Série aérospatiale - Disjoncteurs - Méthodes d'essais - Luft- und Raumfahrt - Schutzschalter - Prüfverfahren - Teil
Partie 404 : Antidéflagration 404: Explosionsdichtheit
This European Standard was approved by CEN on 10 September 2004.
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Contents Page
Foreword.3
1 Scope .4
2 Normative references .4
3 Method .4
3.1 Test mounting .4
3.2 Procedure .6
3.3 Requirement.6

Foreword
This document (EN 3841-404:2004) has been prepared by the European Association of Aerospace
Manufacturers - Standardization (AECMA-STAN).
After enquiries and votes carried out in accordance with the rules of this Association, this Stan
...