The seven most expensive words in low voltage assembly!!!

Image by xdfolio from Pixabay

‘We have always done it that way ….’

By Ludi Erasmus, Director of Modulêr Electrical Assemblies.

FIRST of all, it must be understood that the rules and regulations have changed drastically.
In this article we are only focusing on South African Standards for Low Voltage Assemblies
The current legal document in South Africa is the SANS10142-1 Ed3.1 released in 2021 already.

In this document we will see that SANS 61439-1 as well as SANS61439-2 are mentioned, drilling down to Table 4.1 we will see that Electrical Assemblies are broken down into:
“ ≤ 10 kA short-circuit current low-voltage switchgear and control gear Assemblies that must comply to SANS1973-3 and Assemblies > 10 kA (most Assemblies connected to a Transformer 315kVA and larger) which must comply to SANS 61439-2.”

SANS 61439-1 and 2 are exact copies of IEC 61439-1&2 Ed3 published in 2020, by referring to SANS/IEC61439 in the new SANS 10142, South Africa has actually moved into the IEC 61439 world, there is no more reference in the latest SANS 10142-1 to the old SANS 60439.

So why the change?

Designs and market needs for switchboards have evolved over the years with changing technology in circuit breakers and a lot of new multinational component manufactures entering the market.

It is not practical to fully type test every conceivable configuration of assembly produced.
Where type testing is not feasible, there has to be alternative ways of ensuring an assembly meets the minimum required safety and performance criteria. The methods for proving the design of a partially type tested assembly in accordance with IEC60439 and old SANS1973-1(pre 2017) is weak and rely entirely on the capability of the panel builder, The new standard focuses on temperature and heat dissipation and this is all taken in to effect when fitting components and copper busbar; no longer is height x width x 1.6 = to current caring capacity. Most multi nationals now dictate what the minimum recommended size of copper connections are and in some cases even the orientation that will have an effect on current.

If we take the published installation rules of a well known multinational we will see that for a 2 500A Air circuit breaker their min/recommendation is for horizontal tags 2 x 100 x 10 Copper and for Vertical tags will be 2 x 80 x 10 Copper which then also gets downgraded if the breaker is in an IP31 enclosure to 2 250A and an IP54 enclosure to 2 000A only, so if your client has a load of 2 500A you will now have to install a 3 200A breaker with
horizontal bars of 3 x 100 x 10 for 2 800A in IP31 or 2 500A in IP54 , or 3 x 80 x 10 in vertical, with rating of 3 100A in IP31 or 2 700A in IP54.

So now you can see that to comply has strict rules to follow from the multinationals as well and it becomes very expensive to build the way you always have built and your equipment will start failing!