In response to the question “What’s the difference between standards IEC 60898-1 and IEC 60947-2?”, I’m tending to answer with another question: What do they have in common? They are both standards that specify requirements for low-voltage circuit breakers. Is there more in common? Let’s look into.
IEC 60947-2, which I introduced at length in the first of these blog posts, governs CBs for industrial applications. They protect electrical power distribution of up to 1000 volts a.c. and 1500 volts d.c. with whole spectrum of rated current from 0,5 to 6300A. Utilities and manufacturing facilities use them: air circuit breakers (ACBs), molded case circuit breakers (MCCBs) and miniature circuit breakers (MCBs).
As for IEC 60898-1, it relates to the a.c. low-voltage circuit breakers – MCBs – we find in our homes, schools, shops, and offices electrical distribution switchboards. The standard states that the top rated current is 125A, while the lowest is 6A and maximum value of rated short-circuit capacity (Icn) is 25kA. Just those basic tech specs tell us how different the use of circuit breakers defined by our two standards are.
Many more differences and IEC 60898-1 and IEC 60947-2?
Yes. The rated voltage currently required in industrial-use CBs is 440, 690 volts or higher. Compare those numbers to the 400V upper limit between phases for residential MCBs. Reference ambient temperatures are 30°C for households. The same goes for impulse withstand voltage (Uimp). IEC 60898-1 requires 4kV, in line with the use for final circuits. Whereas for industrial circuit-breakers, usual values of Uimp is 6 or 8kV, in line with the position of the circuit-breaker, at the origin of the installation.
Who confuses the two standards and how?
Users confuse – particularly “prescribers”, e.g. those people who draw up specifications in invitations to tender. Procurement managers in utilities, too, can get things wrong. As to how they mix up the standards, I can’t say. But happen it does.
The history of standard IEC 60947 may have something to do with it. The concept behind it as it evolved in 1970s-80s was a single standard for all low-voltage switchgear. That notion, combined with lack of knowledge or technical expertise, may have led to the misconception that there is one standard for all CBs. Of course, it wouldn’t matter so much if people thought it was IEC 60947-2.
Can IEC 60898-1 be used instead of IEC 60947-2?
No. Consequences can be dire if residential CBs are used instead of industrial ones. An MCB designed for indoor, pollution-free conditions would be woefully inadequate for harsh, outdoor applications that require pollution degree 3.
Or take the tripping characteristics: IEC 60898-1 clearly describes B, C and D curves with ratio to rated current, while in IEC 60947 2 the instantaneous tripping release may be adjustable according to the need of the user or pre-defined my manufacturer with ±20% tolerance. This is the reason why manufacturers in addition provide a wide scope of different curves: K, Z, MA.
Typically IEC 60898-1 certified CBs meet minimally required performance to proof proper protection of household installations: Pollution degree 2, impulse voltage 4kV, isolation voltage is the same as nominal voltage 400V. That is the reason why usually we meet limited number of printed technical information on CBs.
Where should be used IEC 60898-1 certified CBs?
These CBs are intended for use of indoor, pollution and humidity-free conditions: household or similar installations overcurrent protection by uninstructed people and not being maintained. In other words – in final distribution electrical switchboards of buildings which nominal current does not exceed 125A. Usually these circuit breakers sold by electrical retailers: simple to install, safe and easy to use even after many years without maintenance.
The most suitable solution for use are MCBs certified with both standards as their performance meets requirements of use for residential installations and high enough for use in industry and infrastructure applications. Due to high level of protection performances these CBs should be used at least in incoming electrical switchboards of buildings applications.
I can say is that mix-ups of standards happen. The best way to avert them is tightly worded, highly enforced national regulations. And for prescribers to specify what CBs will be used for and then to check the standard for that use.
Have you ever mixed up the two standards? Leave us your comments below!