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Informationen to IEC 61439

In 2012, the restructuring and revision of the safety requirements for low-voltage switchgear was finalized with publication of the standard, IEC 61439-1:2012. The preceding standard, IEC 60439-1 will be replaced by IEC 61439-1:2012. The former Standard IEC 60349 is valid until 24/09/2014.
After this specified date, the use of IEC 61439 is mandatory (for all new designed switchgear and control gear assemblies) the planning and documentation must be executed in accordance with IEC 61439-1:2012 and its parts. The purpose of this standard is the harmonisation of most of the general regulations and requirements for low-voltage switchgear and control gear assemblies to achieve uniform requirements and verifications for switchgear and control assemblies and to avoid the necessity of verifications in accordance with other standards.
All requirements of the different switchgear and control gear assemblies have been combined in this fundamental standard, together with topics of broad interest and application, e.g heating, insulation properties, etc.

In the future two main standards will be required for each design of a low-voltage switchgear and control gear assembly:
❐ The basic standard that is referenced as "Part 1" in the specific standards;
❐ The applicable parts 2 to 7 of the switchgear and control gear assembly standard that deals with the particularities of the application.

The new IEC 61439 consists of the following parts:

New IEC ...

Replaces IEC ...


General definitions



Power switchgear and control gear



Distribution boards



Assemblies for construction sites



Public cable distribution cabinets



Busbar trunking systems



Draft – specific installations on public
sites, marinas, campsites, market
squares, and EV charging stations


Requirements in this standard, which are object of an agreement between manufacturer of the switchgear and control gear assemblies and user, are summarized on the following pages. This listing facilitates provision of information concerning basic conditions and supplemental user definitions.

Replacement of TSK and PTSK through design verification
The previous terms, like type-tested (TSK) and partially type-tested low-voltage switchgear and control gear combinations (PTSK), as well as the type test for confirmation of compliance with standard specifications in accordance with IEC 60439 do, no longer apply. Instead, the design verification is now used. In addition to this design verification, a piece verification must also be provided, which ensures a correct installation in accordance with the standard, the exclusion of material defects, and compliance with electrical safety requirements.

Definition – "original manufacturer" and "manufacture of the switchgear control gear assembly"
Original manufacturer

Organisation / enterprise that executed the original design and the associated verifications in accordance with the standard.
Manufacturer of the switchgear and control gear assembly
Organisation that completes a device and assembles it into a functional unit. The manufacturer is responsible for piece verification and thus for the product (Declaration of Conformity).
Significance for MENNEKES products:
For ready-wired devices MENNEKES is simultaneously the original manufacturer and the manufacturer. The responsibility and provision of verifications rest with us. We cannot declare partially wired devices that we manufacture as standard compliant. In this case the "finishing entity" becomes the manufacturer and must declare conformity. It is required to forward information to this organisation so that the device ultimately can get a "Declaration of Conformity".

The max. ambient temperature is +40 °C. The average value of the ambient temperature over a period of 24 hours must not be higher than +35 °C.
The verification of heating can be provided through various methods. Through testing of the switchgear and control gear combination, or through derivation of a known reference, and through an expert assessment, e.g in accordance with applicable design rules.
Regardless of the method that is selected to determine the heat and thus the maximum current load of the combination, compliance with the appropriate temperature limit values must be ensured.
The switchgear and control gear assembly and its electrical circuits must be capable of bearing their rated currents under defined conditions and the rated values of the components, their suitability and application must be taken into account, without exceeding limit values specified in IEC 61439-1 Table 6, Part 1. The limit temperatures in Table 6 apply for the average ambient temperature of +35 °C.
▶ The limit temperatures of the installed equipment must be taken into account!

Heating – replacement of components
A device/component may only be replaced through a similar, identically constructed device a of a series other than the series used in the verification, if the power loss, and thus the heating of the connections is less than or equal to that of the device that is being replaced.

Load of the largest electric circuit and of all outgoing circuits individually with rated current
The requirement of IEC 61439 is, that all electric circuits must be individually capable to carry their rated current, without exceeding temperature limit values in the process.
If additional power circuits are added, a rated load factor can be set.
Rated values InA, Inc, RDF

❐ Standard definition InA
The rated current of the switchgear and control gear assembly, InA, is the total current that the main busbar can distribute in the respective installation of the assembly, without exceeding the temperature limit values mentioned in IEC 61439-1 Section 9.2!
The current, InA, is considered to be the maximum current that the assembly can distribute via its outgoing circuits at 100% continuous duty (CD).

❐ Standard definition Inc
The rated current of an electric circuit is the value of the current that can be carried by this electric circuit under standard operating conditions when it is operated alone. The assembly must be capable of carrying this current without exceding the max. temperaturelimits of the individual components specified in IEC 61439-1 section 9.2.

❐ Standard definition – rated diversity factor RDF
The RDF is the specified percentage value of the rated current with which the (individual) outgoing circuits Inc of a switchgear and control gear assembly can be continuously and simultaneously be used with due
consideration of the opposing thermal influences. In this process the InA must not be exceeded.

Table 101 from IEC 61439-3 
Values for assumed load

Number of main
electric circuits

Assumed load factor

2 and 3


4 and 5


6, up to and including 9


10 (and more)


This table provides guide values, if in doubt the manufacturer's specification always applies.