MK 6 AMP TYPE 2 M6 MCB CIRCUIT BREAKER 240V LN 5906 BS 3871

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K~ 145 for rubbers and 115 for PVC insulation , with certain assumptions about starting temperature. Max Zs is the maximum permissible values of earth fault loop impedance (Ω), some maximum Zs values are listed in BS 7671, the maximum earth loop impedance values listed in the Zs tables are used to compare against the actual measured earth loop impedance values to ensure compliance with BS 7671. Section 536 is about ensuring (amongst other aspects) that the performance of devices for protection against faults and overloads are coordinated so that the effectiveness of the operation of individual items of equipment, under both normal and abnormal operating conditions, does not impair the safety or proper functioning of the installation. It includes, for example, the set of regulations that provides requirements for selectivity of protective devices for residual currents, overloads and short-circuits. Type 3 SPDs provide local protection for sensitive equipment. As these have a relatively low discharge capacity, they should always be installed in addition to a Type 1 or 2 device. Indeed as Mike mentioned 10ms gives a very large number (for 3kA and 10ms -->> energy let through is 90000).

If you are looking for reason to keep the existing despite the mains upgrade, then you will need more data, but don't be surprised if it doesn't help much - do you know for example if it was compliant before the upgrade took place (ie at the previous fault level) - have you tried a random MCB is say Amtech (or data from a different supplier)For this reason, while fuses can be cascaded, and if the thin one blows, the fatter one behind it will not, for all values of fault currrent, for MCBs no such statement can be made. Indeed it is common to find a random selection of breakers open under fault, and for really high current faults the fuse at the origin fails instead.

Let through energy is a bit problematic for breakers - a fuse gets faster as the fault current rises, and tends towards a constant let- through energy (I squared r times time, but the resistance r is a fixed parameter of the fuse, as is the weight of metal to be raised to melting point to start it breaking) IF you put in the maximum breaking time of 10ms you will come up with a very large minimum cable requirement,and may well (incorrectly) conclude the cable is not protected. Now for something nifty: the _instantaneous_ voltages between points must always add up. If I measure 5V (DC) from A to B, and 6V (DC) from B to C then I will get 11V from A to B. If I measure 5V from X to Y and 6V from X to Z, then I will measure 1V from Y to Z. Finally , if I measure 5V from A to B, I will measure -5V from B to A. But this is all DC, or instantaneous voltage. For this reason, regulation 536.4.203 states that ‘The relevant part of the BS EN 61439 series shall be applied to the integration of mechanical and electrical devices and components, e.g., circuit-breakers, control devices, busbars into an empty enclosure or existing low voltage assembly.’ Now I’ll set up a nifty little tool; a special transformer that lets me produce output of arbitrary phase angle. The output is still 277V RMS relative to our zero reference, but I can shift its phase relative to phase A. Lets call the output of this transformer ‘phase W’. I adjust phase W so that it is very slightly delayed from phase A, and graph the two phases.

So the Zs calculation formula for a 0.1s to 5s disconnection time for a BS EN 60898 MCB or BS 3871 to calculate the maximum Zs would be: The reference calibration temperature for types B, C or D shallbe 30 'C and for types 1 , 2 , 3 and 4 shall be either Protection against transient over-voltages shall be provided where the consequence caused by over-voltage: