Whoops, you don’t have access to that! Please register with the IET to join the community and access this area. In your given example its not exactly as you name it: for iC60N range the 50kA Icu is only for breakers in range of 0,5-4A, for the rest of the range it is 10kA.

If I understood your question well, the difference comes from ratio of nominal Icn and ultimate Icu breaking capacities ratio to service breaking capacity Ics. It is usually stated in percentage 100%, 75%, 50% or less. As higher this value as more “robust” breaker to withstand Ics. Two standards that specify requirements for low-voltage circuit-breakers (cbs) have been causing confusion for some time among designers and installers of electrical installations. They are BS EN 60898-1 and BS EN 60947-2 and questions are often asked about the difference between them. Yes. The rated voltage currently required in industrial use CBs is 400 V, 440 V, 690 volts, or higher values up to 1000 V. Compare those numbers to the usual value 230V/400 V for residential MCBs. Reference ambient temperature is 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, the usual values of Uimp are 6 or 8kV, in line with the position of the circuit breaker at the origin of the installation. In many European countries there is no table, they only have the formula in their national standards. Note that BS7671:2018 clause 411.4.202 does state that the permissible Zs can be calculated and in my opinion it is the best method to ensure that we are not failing Zs values that are still low enough to achieve the required disconnect time. I will give you an example: 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

A circuit is protected by a 20 A type B circuit-breaker to BS EN 60898. The ambient temperature is 20 oC and the circuit is wired in 2.5 mm 2 twin with cpc thermoplastic cable. Calculate the maximum measured Z s. higher permissible loop impedance using 240Vac in our calculations as per BS7671:2018 clause 411.4.4 ( Zs × Ia ≤ U0 × Cmin). But I’m still confused in case of MCBs that have 2 condition of breaking capacity depend on which IEC that MCB comforting to https://blog.se.com/power-management-metering-monitoring-power-quality/2013/07/16/iec-60947-2-the-all-risk-insurance-for-circuit-breakers/

is used and then corrected by a Cmin of 95% so use 218.5V (which should actually be 94% for the minimum allowed voltage and 216.2V). Dear Sahad, it is normal having MCCB certified as per 947 in commercial/small commercial buildings with MCB’s certified as per 898. And it is wrong to use MCB’s dedicated for domestic applications (60898) in industrial applications installations. From Table B6 of the OSG, the maximum measured Z s value is1.75 Ω at an ambient temperature of 10 oC. As mentioned in the blog, MCB manufactured as per IEC 60898 to be used in residential buildings or similar applications. In industrial applications can be used breakers certified as per IEC 60947-2 or IEC 60947-2 and 60898 both.Circuit-breakers to BS EN 60898-1 can also comply with BS EN 60947-2 but the short-circuit breaking capacity of each may be different. Some manufacturers state that their cbs with a short-circuit capacity of say, 10 kA comply with BS EN 60898-1 and the same cb with a short-circuit capacity of 15 kA complies with BS EN 60947-2. There will be circumstances where a designer has specified requirements which are particular to an electrical installation. I am being told by an inspector that we have to use 230Vac when performing permissible earth loop impedance calculations as per BS7671:2018 clause 411.4.4 Zs × Ia ≤ U0 × Cmin. 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.

From your article I get that IEC 947-2 has stronger specs more than IEC 898-1 such as ( Ue , Ui , pollution degree) but how Icu for 947 ( stronger conditions ) can be greater than 898 for the same MCB Usually it is recommended to use D, K or MA curves MCB’s to protect inductive loads. Typically: C curve: Ii=5 to 10 In, D curve: Ii=10 to 14 In. Circuit-breakers are primary circuit protective devices. They are not intended for frequent switching of loads. Infrequent switching of cbs on load is admissible for the purposes of isolation or emergency switching. 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 are safe and easy to use, even after many years without maintenance. They are suitable for Pollution Level 2 and their classifications and applications are shown in Tables 1a, and 1b.

Where should IEC 60898-1 certified CBs be used?

A frequent enquiry Stroma Certification receives is regarding the maximum values of earth loop impedance (Z s) for legacy circuit breakers manufactured to BS 3871. The maximum values of Z s for BS 3871 circuit breakers were published in The Wiring Regulations up until the 2001 edition of BS 7671. Regulation 510.3 of BS 7671 requires that every item of equipment selected and installed must take account of the manufacturer’s instructions. Dear Mostafa, in IEC 898-1 it is mainly used definition of Icn (rated (nominal) breaking capacity) but not Icu (ultimate breaking capacity) and it makes the difference.

An MCCB with a rated current value (I n) of 32 A is connected to a circuit forming part of a TN supply system which has a U 0 value of 230 V. The MCCB is required to disconnect in 0.4 seconds. Calculate the maximum Z s value. MCCB standard is IEC60947 and MCB is coming under IEC 947 & 898. So what is your opinion of using MCCB-947 & MCB-898 in a single distribution for a residential/commercial buildings. Also any problem occurs if using IEC898 MCB in industrial applications. Manufacturers warn against installing circuit- breakers of one manufacturer as replacements for cbs of another manufacturer, without the necessary verification of performance. This standard BS EN 60898-1:2019 Electrical accessories. Circuit-breakers for overcurrent protection for household and similar installations is classified in these ICS categories: Maximum Z s values for MCCBs to BS EN 60947-2 are not included in BS 7671. Therefore, manufacturers’ tables should be consulted for the rating of the MCCB to be used.How comes BS 88 and bs1361 fuses have two tables for 0.4s and 5S but 60898 fuses have one which covers both.