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Unless the transformer is very large the true PFC will not be anywhere near 40 kA. As an example a 1000 kVA transformer with a per unit impedance of 4.8 % would only produce a PFC of 28 kA at its terminals. A 2000 kVA transformer with 6.0 % pu impedance would give just over 40 kA but...

Well first the R1 + R2 test is not a requirement of BS 7671 - but assuming you like doing it - what does it actually tell you? Now you could go on, as you describe, and measure Rn + R2 and it is just possible that your results might identify a problem. However that would very much depend on...

Is it a basic requirement - by that do you mean that is easy to do, or do you mean that it is essential for safety? What exactly are you hoping to confirm from your "measurement of continuity"? What does measurement of continuity mean - a circuit is continuous or it is not. Do you...

First you would need to get a bit more detail. Next - I am not quite sure what you hope to achieve with a current / time graph. I assume you are trying to determine if the 315A fuse will provide 'backup' protection to the mcb. If so you need to know the Let Through Energy of the fuse...

Do you call that putting the cat among the pigeons :D You don't do it like that - you do it like this - First please find a regulation in the national standard BS 7671, or its parent IEC and CENELEC documents that requires that I measure R1 + R2 on initial verification or a PIR...

Class 2 wiring systems do exist and some are very large - http://www.eaton.com/EatonCom/ProductsServices/MEM/LiteratureLibrary/index.htm Look at the PDFs on the Halyester systems. In the domestic environment there are quite rare but you may consider the 'double insulated' tails from...

This question has been answered many times. Paul Cook addressed it pre 2004 see here: http://www.theiet.org/publishing/wiring-regulations/mag/pre-2004/ and open the PDF on earthing plastic pipes. Note the resistance of tap water in a 15 mm pipe. The Electrical Research Association (ERA)...

martinxxxxxx said I suggest you read 412.2.4.1, and then section 412.2 generally :D

530.4.2 is at the root of this. The 'fabric of the building' is not defined. Now if you choose to interpret this regulation to mean accessories cannot be fitted to kitchen units - you have a problem with supplies to 'island units' :D. The regulation refers to 'unenclosed equipment' -...

To those who believe that bonding creates an equipotential zone please look at the definitions in the 17th Edition - you will find that the term 'Earthed Equipotential Zone' has been omitted - why - because there is no such thing in an electrical installation under fault conditions...

All ships do not have two rudders - I was in the Merchant Navy for about seven years in total and I supervised five major refits in dry dock - so I think I would have noticed :D. IT systems gain favour because of the reduced fault current and increased reliability. They do have there...

IT systems - lets restrict this to LV systems derived from either the secondary winding of a delta star HV / LV three phase transformer or from an LV three phase alternator with a star winding. In both cases then we have a star point - just like a normal TN distribution system. The...

Ah DC ships I remember them well :D. My first vessel was the SS Benloyal - built in the late 50's she had a steam turbine and a destroyer shaped hull. She managed 28 knots in sea trials but damaged her gear box and was later restricted to 21 knots service speed. She was probably the...

Leaving ships out of it for now - Looking at the supply network we could put forward a number of reasons for referencing it to earth. Taking just two: 1) It simplifies the problem of selecting the correct amount of insulation required for cables. 2) It facilitates the use of a simple...

First I agree that you should get an electrician to check it out for you. Now this can occur with gas supplies that have steel supply pipes that also connect to other properties. This is likely if you have a pme (TN-C-S) electricity supply system. If you have there may be a notice at the...

What a load of old tosh - just whack a self tapper in, or a wood screw :shock: :D Now where did I park me horse - ye ha :D

I am quoting the temperature range for performance tests given in BS 1363-1 1995. BS 1363-4 1995 deals with connection units (FCU). Both standards give an operating range of -5 to +40 degrees with the average temperature over 24 hours not exceeding 25 degrees. The use of plugs and...

BS 1363 plugs are designed to work in 'normal temperatures'. The standard requires that performance tests are carried out in an ambient temperature of 20 +/- 5 degrees. The ambient temperature in many airing cupboards would exceed this - so the use of 1363 plug and sockets is usually...

Dr Who could probably measure peak to peak voltage directly, but mere mortals could not :D.

What do you think the continuous rating of a two gang 13A socket outlet is then :D. A quick check in BS 1363-2 1995 points to an answer - and its not 26A :shock: .