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

Product Information

That just because individual components conform to their respective product standards and are UKCA marked, it does not indicate their compatibility for integration into an assembly. So now we have the two important facts: voltage is measured between two points, and an AC voltage is an average over time. 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. If you are looking for a reason to scrap the existing, then absence of that data is as good a reason as any I don't for one moment think we need to use 3000 A for 0.1 seconds in this case but if you did then the 300 becomes more like 1000, and the minimum cable size is probably 10mmsq....

The correction factor is 0.8, this 0.8 correction factor is to allow for the rise in temperature under fault conditions.

New Requirements

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. Indeed as Mike mentioned 10ms gives a very large number (for 3kA and 10ms -->> energy let through is 90000). 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. Protection against transient over-voltages shall be provided where the consequence caused by over-voltage: The 100% values should be recorded as the maximum permitted Zs value on the electrical test certificate and the temperature adjusted 80% values are used to compare against the actual readings obtained when testing the circuit. 60947-2 Max Zs Values

This is developed in Note 2 to regulation 536.4.203, which states that ‘ If an assembly deviates from its original manufacturer’s instructions, or includes components not included in the original verification, the person introducing the deviation becomes the original manufacturer with the corresponding obligations’. 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 When carrying out an earth loop impedance test you are carrying out the test under normal conditions, so to take into account of the rise in cable temperature under fault conditions we need to apply the 0.8 correction factor to the maximum Zs value, therefore 1.37 * 0.8 = 1.096 (rounded to 1.1) which you then compare to your test results.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. A Type 1 SPD is designed to provide protection against surges caused by direct lightning strikes. These often feature spark gap technology, which can handle very high voltages by creating a short to ground when a level of current is reached. Type 2 To see how AC voltages add up, we have to remember that the AC voltage is a form of average, and we have to look at the instantaneous values, get an instantaneous sum, and take the average of that. On a slightly more benign note, circuit-breakers are designed to run warm in normal conditions when carrying load current. The thermal performance of the assembly is considered in BS EN 61439 to ensure that the internal temperature is not excessive and the operation of protective devices is not impaired – when excessively warm for example, the thermal overload operating current of a device will reduce, potentially causing premature operation. Excessive temperatures may affect the control circuits of electronic equipment mounted in the enclosure.