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                          IEC Standards FAQs


                          1) What are the differences between the new and the former standard?

                          Basic points:

                          • Acknowledgement of the “Assembly systems” manufactured by an “original manufacturer” and put at the disposal of final “Assembly manufacturers”.
                          • Confirmation and clarification of a number of safety or reliability requirements.

                          2) Which part corresponds to panels?

                          IEC 61439-2 is specific to “Power switchgear and control gear Assemblies”; i.e. power switchboards; it is based on the IEC 61439-1 general rules.


                          3) Why have the different parts of the standards (switchboards, busbar trunking…) changed?

                          The structure has changed to be consistent with the IEC 60947-X switchgear and  control gear standards. The power switchboards are now covered by a specific  standard, IEC 61439-2, whereas it was covered by a general rules standard.


                          4) Is the standard in force for all kinds of LV Assemblies (switchboards, busbar trunking...)?

                          No. Only IEC 61 439-2 for power assemblies and IEC 61 439-1 for general rules are  available. The other parts are scheduled by 2011. That’s why the IEC  60439-1 & -2 standards are still valid for the busbar trunking systems.


                          5a) Should the tests carried out according to the IEC 60439-1 standard be repeated according to the new standard?

                          No. It is only necessary to carry out the additional tests, such as the temperature rise test  of each circuit loaded with its rated current and the lifting test.


                          5b) My question is regarding panel builders using Schneider Electric devices (CBs…) in their own switchboard systems : What do they have to do to comply with the new IEC? Is it enough to do the new tests (lifting test…), or should they re-do some tests (heat-rise, short-circuit) and which ones?

                          Tests according to IEC 61439-1 already made according to IEC 60439-1 need not be repeated. Only the new tests have to be made.
                          However, the new standard is more strict about the compliance of variants based on tested reference configurations;It means that a single tested configuration is generally not enough.


                          6) Who of the original manufacturer and of the switchboard manufacturer is responsible for the switchboard?

                          The new standard takes better into account the organisation of the market and clarifies the allocation of responsibilities.
                          As before, the panel builder is responsible for the final switchboard by designing it according to his customer’s specifications and to the “original manufacturer’s” instructions, and by carrying out the routine tests.
                          The original manufacturer is still responsible for the design of the Assembly system and for the quality of the parts he sells.


                          7a) Today I carry out a temperature rise test on switchboards equipped with a given manufacturer’s devices and when I use the devices of another manufacturer I calculate the power loss according to the data given by the manufacturer => Does the same apply to the new standard?

                          This practice complies neither with the former standard nor with the new one.
                          Regarding temperature rise, the standard requires strict conditions to allow substitution of a device by another one:
                          The rated current and the physical arrangement must be maintained (in particular the length and cross-section of the connections)
                          The power loss of the new device must be the same as or lower than that of the initial device
                          The temperatures of the terminals of the new device when it’s tested according to the IEC 60947-X standard must be the same as or lower than those of the initial device
                          NOTE: In addition, all the other checks must be repeated, especially the short-circuit test.


                          7b) Can you tell us precisely which paragraph(s) of the new IEC explain the conditions under which a test made with one device (for example a Schneider Electric one like Compact NSX) can be used to validate a performance with another device (for example ABB one)? for heat-rise,short-circuit...

                          Devices substitution is practically impossible because both following conditions must be fulfilled:
                          Temperature rise (sub-clause of new IEC61439-1), the alternative device must have;
                          a power loss less than or equal to the original device;
                          the temperature rise on its terminals that is less than or equal to the original device when both are tested in accordance with the same product standard
                          and physical arrangement within the functional unit must be the same.
                          Short circuit (table 13 from sub-clause 10.11.3 of new IEC61439-1), substitution is only permitted when:
                          * the original and substitute device are from the same manufacturer, and;
                          * the device manufacturer is prepared to certify the alternative device is equal or better than the original device in all relevant respects.


                          8) Because there are many more verification methods, can I comply with the new standard without carrying out tests?

                          No. Just like the former standard, the new standard is still mainly based on type tests.
                          It defines more accurately the verification of a variant by comparison with a configuration already tested.
                          Furthermore, but for temperature rise tests only, the new standard gives two calculation methods based on safety margins and applicable within tight limits of power and complexity of the switchboard.


                          9) Do I have always to use partitions for doing forms 2 to 4?

                          No, separation may be achieved by means of partitions or barriers, but also (it is new) by insulation of live parts or integral housing of a device e.g. a moulded case circuit breaker.
                          For instance in Prisma, In case of mounting the breakers horizontally, using terminal shields each breaker will be at FORM 4 A:=



                          10) The new standard specifies a test of 200 operating cycles for locking and interlocking means and for removable parts, instead of 50. Does this test include also devices like Circuit Breakers?

                          No, the test has to be done only on the parts of the switchboard like doors or drawers. Tests for devices like circuit-breakers are done separately according to the IEC60947-X Series.


                          11) I have heard that for temperature rise tests it is allowed to use Heating resistances instead of devices? Is it true?

                          No, the tests done for a functional unit or an assembly have always to be done with a specified device. Heating resistances could only be used to simulate the heating effects of the devices around the tested functional unit or assembly.


                          12) As a Panel Builder using an assembly system I newly have to do an Impulse withstand voltage test and will have to invest in a new test equipment. Is that true?

                          In the main cases this is not true. IEC 61439-1&-2 Edition 1 specifies an impulse withstand voltage test, that may be replaced by a measurement of the clearances, provided these clearances are larger than 1,5 times the specified values.
                          The future mid 2011 Edition 2 of IEC 61439-1 and -2 will come back to requirements similar to 60439-1, i.e. visual inspection of the clearances only, provided this inspection is practicable and these clearances are larger than the specified values; otherwise a measurement or a voltage test must be done. So the investment is not worth.


                          13) there is a new requirement about designation marking durability. What does it mean?

                          That means that all marking information related to safety issues should be done in a way that they will be always readable and accessible during the whole life of the assembly.

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