Of note here is that a protective device may conform to the appropriate product standard (e.g. BS EN 60898) and be UKCA marked. If the devices are from different manufacturers, they are likely to be designed differently and will perform differently – though both may comply with the appropriate safety requirements of BS EN 60898. Step 2 remember that for AC circuits the voltage is a constantly changing value, and when we give a single number, it is a form of average voltage, called the RMS voltage. The RMS voltage of an AC waveform corresponds to the DC voltage which would deliver the same power to a resistive load. If you take AC at 480V RMS and apply it to a 480 ohm resistor, the average power delivered to that resistor would be 480W. If you take DC at 480V and apply it to a 480 ohm resistor, the power delivered to that resistor would be 480W. 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.

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’. Before delving into the detail of this change, as ever it pays to start at the beginning – namely the Fundamental Principles of Part 1. 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. The last bit is to ask ‘how do I calculate the voltage difference between two phases with some other phase angle?’ Clearly this is some function of the amplitude of the phases, and also a function of the phase angle between them. Simplify the question by stating that both phase A and phase W have the same phase to neutral RMS voltage V. Call the phase angle between these two phases T. The voltage between the phases is then given by V * 2 * sin(T/2). So for the 180 degree phase difference we get V * 2 * sin(180/2) = V *2

New Requirements

The values of earth loop impedance shown in these tables must compensate for conductor temperature rise, if the measurement of loop impedance is taken at ambient temperature. A useful rule of thumb is to allow for a temperature rise from 20 degrees to 70 degrees by multiplying the listed value by 0.8. The measured value can then be compared to the compensated value. Make a graph of the difference between A and W, and you will find out that it is a sine wave with low amplitude. In fact, it is a law of mathematics that the sum or difference of two sine waves of the same frequency (but possibly different amplitudes or phases) is another sine wave of the same frequency, again with different frequency or phase. 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) Every item of equipment shall comply with the appropriate British or Harmonized Standard.’ For distribution boards, this is the BS EN 61439 series. Part 3 is a specific part of the BS EN 61439 suite and it includes requirements for Distribution Boards intended for use by ‘ordinary persons’. 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.

should be taken as soon as possible to improve the safety of the installation." would be appropriate but maybe your not talking about the LoadMaster In summary, can you mix devices in distribution boards (including consumer units)? Yes, you can. But you need to seek assurance from the manufacturer of the original assembly that the devices will be compatible, or conduct your own study to ensure the requirements are met. In the words of BEAMA, ‘The installer has responsibility to act “with due care”. If this is not done then there is a probability that, in the event of death, injury, fire or other damage, the installer would be accountable under Health and Safety legislation.’ The Dorman Smith Loadmaster was very common years ago and because not a din rail mount very hard to replace without whole enclosure replacement but I seem to remember there was only a thermal trip in them and not a magnetic type as well so they would not have a number or letter just a current rating.Protection against transient over-voltages shall be provided where the consequence caused by over-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 Originally there would have been a graph like we still get for a fuse and I would not think they would comply with BS7671:2008 and will need replacing to comply. Not sure what I would code it as? I think Code 2 "(Requires improvement) This code is to be used to indicate that the observed deficiency requires action to remove potential danger.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.’ OK - I was assuming 90C/250C (ie XLPE insulation and K of circa 150) so you should be OK for 2.0mm2 and upwards - which should exclude a whole load of circuits from your assessment. Indeed as Mike mentioned 10ms gives a very large number (for 3kA and 10ms -->> energy let through is 90000). 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. MCB (Miniature Circuit Breaker ( BS 3871 ) is a mechanical device operate automatic operation designed to connect and disconnect the electrical circuit in the ordinary and extraordinary situation.Suitable for AC and DC voltage.It mean main function is to protected equipment or circuit from overload and short circuit.