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: 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. 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. I am also being told from an inspector that the permissible disconnection time in table BS7671:2018 41.1 is 0.4 seconds.

The table is based on nominal rather than actual voltage - 230V nominal is usually taken to be anything within the -6% to +10% range - i.e. between 216.2V and 253V. It's very common for DNOs to have far above 230V at their transformers to compensate for voltage drop in the distribution system - typically a 433/250V. So as long as your supply doesn't go above 253V (during times of low load say) I'd say it's acceptable to use the 230V nominal column (e.g. 0.4s for TN small final circuits). Where a more frequent switching is required, such as the switching on and off of banks of luminaires, the manufacturer’s instruction should be followed and preferably an alternative device should be selected. 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: 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. How comes BS 88 and bs1361 fuses have two tables for 0.4s and 5S but 60898 fuses have one which covers both.A cb designed for Pollution Level 2 conditions would not be suitable for harsh outdoor or humid applications that require Pollution Level 3. However, as the resistance of conductors tends to increase with temperature, the ambient temperature at which testing is carried out is a significant factor in determining the temperature (and therefore the resistance) of conductors. IEC 60898-1 relates to a.c. low-voltage circuit breakers for household and similar applications– also known as MCBs (miniature circuit breakers)– which we find in homes, schools, shops, and office electrical distribution switchboards. The standard states that the maximum rated current is 125A, while the lowest is a few amps, and the maximum value of rated short-circuit capacity (Icn) is 25kA. Those basic tech specs alone tell us just how different the use of circuit breakers (CBs) are as defined by the two standards. Many more differences between IEC 60898-1 and IEC 60947-2?

IEC 60898-1:2015 applies to a.c. air-break circuit-breakers for operation at 50 Hz, 60 Hz or 50/60 Hz, having a rated voltage not exceeding 440 V (between phases), a rated current not exceeding 125 A and a rated short-circuit capacity not exceeding 25 000 A. This second edition cancels and replaces the first edition published in 2002, Amendment 1:2002 and Amendment 2:2003. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition: One of the more common types of BS 3871 circuit breaker found on installations is the Crabtree C50 which was produced in single phase and 3 phase versions. These are all Type 2 circuit breakers and their fault current rating can be determined by the infill paint in the operating handle. White paint infill indicates a 3kA rating and yellow paint indicates a 4.5kA rating. However if we perform the calculation using 230Vac will will get a reduced permissible Zs. This would seem to suggest to me that we could be failing Zs values that allow enough current to flow in the event of a fault to trip the fault protective device. If it was a curve of disconnection times versus voltage in the regs and not a table no one would care, as 230V and 240v would have times very similar.Any installer who plans to substitute a different cb must obtain authority from the assembly manufacturer to do so in compliance with Regulation 536.4.203. Otherwise, responsibility for the testing and integrity of the compatibility between devices would be down to the contractor. When this is not carried out, there is a probability that, in the event of an accident, fire or other damage, the installer would be accountable under Health and Safety Legislation. For example, the BS EN 60898-1 standard describes B, C and D operating curves with ratio to rated current. But the BS EN 60947-2 standard prescribes an instantaneous tripping release which may be provided with a plus or minus 20% tolerance and adjustable as illustrated in Fig. 1. For this reason, manufacturers provide additional curves K, Z and MA to the B, C and D curves.

BS 3871 circuit breakers were also manufactured as Type 4. Generic data cannot be used for Type 4 circuit breakers and the manufacturer’s data must be used to calculate maximum values of earth loop impedance. The more common forms of Type 4 are listed in the following tables, together with their maximum values of Z s, for 0.4s and 5s disconnection times. FEDERAL 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.Two requirements that ensure reliability of circuit- breakers are the ultimate breaking capacity (I cu) and service breaking capacity (I cs). Where manufacturers’ values of Z s for MCBs are used, they will often recommend multiplying the measured value of Z s by a correction factor, to correct for ambient temperature. For example, Schneider, recommend using a factor of 0.8, 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. Alternatively, the maximum Z s value can calculated using the time- current characteristic of the MCCB being used, as shown in Fig. 2 for a 32 A MCCB.