Square D KQ B 32 AMP MCB 240 v BS60898 10B132 A 10Ka CIRCUIT BREAKER

Product Information

The prospective fault current ratings of BS 3871 circuit breakers are indicated by the letter ‘M’ followed by a digit.

In this case, the inspector of the installation should ask for the design criteria or arrange to forward the test results to the designer for verification.However it should be noted that when measuring Zs and accounting for the rise of temperature under IEC 60364 the permissible earth loop impedance is de-rated by 1/3 where as in the UK under BS7671 it is only de-rated by 20%.

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. 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.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. Two requirements that ensure reliability of circuit- breakers are the ultimate breaking capacity (I cu) and service breaking capacity (I cs). Alternatively, the maximum Z s value can calculated using the time- current characteristic of the MCCB being used, as shown in Fig.

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. Whilst these circuit breakers are obsolete, they are fully acceptable to remain in service and some may be more robustly constructed than their modern equivalents. 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. Using ABB curves software we can quickly obtain the required tripping current (Ia) for a 5 second trip = 77. 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.

Does it mean that the trip kA is different when the breaker is used for residential or non residential use? 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. It is important to select the correct type and current rating of circuit- breaker for the environment, circuit and equipment if adequate protection for overcurrent, short-circuit, fault currents and unwanted tripping is to be provided. 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.