A cb designed for Pollution Level 2 conditions would not be suitable for harsh outdoor or humid applications that require Pollution Level 3. Typically IEC 60898-1 certified circuit breakers meet required performance to prove proper protection of household installations: Pollution degree 2, impulse voltage 4kV, isolation voltage is the same as nominal voltage 400V. Also, the requirements of this standard are adapted for non-technical users which is why limited technical information is printed in detail on CBs. Table B6 of the OSG and Table A4 of GN 3 contain maximum Z s values for circuit-breakers based on the cross-sectional area (csa) of the protective conductor and at an assumed conductor temperature of 10°C. Circuit-breakers to BS EN 60898-1 may look identical to those complying with BS EN 60947-2 but they are not necessarily inter-changeable. Circuit-breakers to BS EN 60947-2 are intended for operation by skilled users and they must be maintained. They are suitable for Pollution Level 3, which includes unheated rooms, boiler rooms, industrial and farming areas.

IEC 60947-2 governs circuit breakers (CBs) for industrial applications. They protect electrical power distribution of up to 1000 volts a.c. and 1500 volts d.c. with an entire spectrum of rated currents from 0,5 to 6300A. Utilities and manufacturing facilities often use air circuit breakers (ACBs), molded case circuit breakers (MCCBs), and miniature circuit breakers (MCBs) 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 by the manufacturer, with ±20% tolerance. This is the reason why manufacturers additionally provide a wide scope of different curves: K, Z, MA.

Where should IEC 60898-1 certified CBs be used?

Regulation 510.3 of BS 7671 requires that every item of equipment selected and installed must take account of the manufacturer’s instructions. I am also being told from an inspector that the permissible disconnection time in table BS7671:2018 41.1 is 0.4 seconds. I know 40mS is Max but is this o.k it could be because the house was very old and damp when we started wiring or should i change the RCD. When Z s tests are carried out at an ambient temperature of 10°C, the conductors being tested may be assumed to be also at 10°C. This means that the tabulated maximum Z s values of Tables 41.2, 41.3 and 41.4 need to be adjusted accordingly. For a cable having thermoplastic insulation with a maximum permitted temperature of 70°C, this adjustment can be made by simply multiplying the maximum Z s values in the appropriate table by 0.8 (Appendix A2 of GN 3). However when I look at table 41.1 it is stating that if Uo is 240Vac the permissible disconnection time is only 0.2 seconds.

The maximum Z s values to achieve disconnection time vary with different types of protective devices and also between manufacturers. Appendix 3 of BS 7671 recommends that wherever possible designers use manufacturer- specific data. So a barefoot victim gets exposed to about 120V, and maybe we can have an argument about reduced CPC in twin and earth.I can say is that mix-ups of standards happen. The ideal way to avoid them is with tightly worded and highly enforced national regulations. And, for prescribers to specify what CBs will be used for and then confirm that the standard governs that usage. The values of earth loop impedance shown in these tables must compensate for conductor temperature rise, if the measurement of loop impedance is taken at ambient temperature. A useful rule of thumb is to allow for a temperature rise from 20 degrees to 70 degrees by multiplying the listed value by 0.8. The measured value can then be compared to the compensated value.

Assemblies such as distribution boards are validated with specific circuit-breakers installed and these cbs are usually from the same manufacturer as the distribution board. Where cbs made by a different manufacturer are to be installed, verification will have to be undertaken by the manufacturer of the distribution board to BS EN 61439-2 or BS EN 61439-3. Fitting unverified devices will invalidate any verification and the warranty. I cs is expressed as a percentage ratio of I cu and gives the maximum short-circuit current a cb can break three times and still function in normal service.The most suitable solution is for MCBs that are certified by both IEC standards since their performance meets requirements for use in residential installations and is high enough for use in industry and infrastructure applications. Due to the high level of protection performance of these CBs, they should be used at least for the incoming electrical switchboards in buildings applications. Appliance for MCB’s to standards in different applications of use