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

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The Cmin factor is applied to the voltage to earth (Uo), so if the voltage is 230 the calculation would be 230×0.95 = 218.5 volts. 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. The 17th edition of the IET wiring regulations amendment 3 introduced the Cmin (0.95) factor which reduced the old maximum zs values to allow for the fluctuation of the voltage. Cor 40 O C , lhe purpose of the latter value being to avoid the necessity of de-rating thermaiiy sensitive circuit- I suspect that this latter condition will not be a problem in this case as this is for a specific fault current below the maximum that is already within the scope of the existing installation, so it will be sufficient to do a calculation for the increased let through energy with the new short circuit current.

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’. is a nice number for rules of thumb , 1.6mm is nearly 1/16 of an inch and almost exactly the diameter of 16 standard wire gauge and 16 Birmingham sheet metal gauge, though not american wire, but AWG 14 is ~ 1.6mm dia. )

Types of Surge Protection

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. Now imagine another point in the system, also connected to phase A. If we measure the voltage at this point, we will get the exact same curve. Finally, try to measure the voltage between these two locations. If you look at each instant in time, the voltage _difference_ will be zero. The average of zero is still zero. Net result is that if you measure the voltage between two points, both phase A, you will get zero volts, as expected. All SPDs work by diverting surge currents to earth to reduce the over-voltage to a level that will not damage the components of the system or equipment connected to it. There are three types of surge protection devices: Type 1

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. Which leaves you with the lighting circuits - how far down the cable do you need to go, if the 3kA value is present at the DB, using 1.5mm2 conductors before you are safe again - not far I suspect. K~ 145 for rubbers and 115 for PVC insulation , with certain assumptions about starting temperature. 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)The regulation in question, 536.4.203, was introduced by BEAMA (the UK trade association for manufacturers of electrical equipment including switchgear) to warn designers and installers of the possible dangers of mixing devices from different product ranges or manufacturers in the same distribution board; mainly, but not exclusively, circuit-breakers. When installing a new final circuit for example, if there is spare space in a consumer unit and a circuit-breaker that appears to fit is to hand, it is tempting to use it. Another example is replacing a circuit-breaker with an RCBO to afford better protection for the user.

In other words, adding together CE marked products from one manufacturer with another’s CE marked products does not necessarily equal a CE marked assembly which is compliant with BS EN 61439. This may also be true when mixing product ranges from the same manufacturer. This is reinforced in Note 1 of regulation 536.4.203 which states that ‘ The use of individual components complying with their respective product standards does not indicate their compatibility when installed with other components in a low voltage switchgear and controlgear assembly.’ So now we have the two important facts: voltage is measured between two points, and an AC voltage is an average over time.Additionally, any commercial, industrial, or public building that is supplied by overhead lines requires surge protection – so the majority of buildings will require surge protection. Residential properties will depend on use and occupancy levels. 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. For non-residential properties that do not fit into these categories, a risk assessment must be carried out, a process that has also been simplified in the 18 th edition, detailed in section 443.4 of the IET Wiring Regulations. Where this risk assessment is not conducted, the regulations require that surge protection is implemented. Types of Surge Protection Indeed as Mike mentioned 10ms gives a very large number (for 3kA and 10ms -->> energy let through is 90000).