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Spark123 said: It matters because all large power networks reference earth potential, even if just by capacitive coupling. If you don't know the voltage to earth at some point in the system how do you decide how much insulation to use on your conductors. This is one of the main reasons...

Whether there is any advantage or not is somewhat academic as TN-C-S (PME) is here and it is here to stay. Many wax lyrical about the good old days of TN-S but all systems have advantages and disadvantages. Taken across the world the most widely used system is, in fact, TT. It is mainly...

I have done it a number of times - it is not at all difficult.

Brand new ones that are very sharp :D it can done.

Now does DI mean double insulated? Assuming that it does most cables are not actually double insulated because the outer sheath is there for mechanical protection, not insulation. That said, BS 7671 does recognize that the outer sheath does provide insulation and this is indicated by...

So RCDs for Additional Protection is the must have protection for the future is it. Funny that - the text of 415.1.1 (word for word) was first published in an IEC document in 1982. Its taken us a very long time to get round to implementing this must have essential safety feature :D.

You should check this out http://www.esc.org.uk/forum/forum_nd_thread.html - look for NDQ14 and the answer. This advice has recently been changed to specifically mention the need for a CU of all insulated construction after some fine fellow convinced the ESC of the error of their ways. They...

Well maybe we should all comply with a manufacturer's instructions, whatever they might be. How about this one: Installation should be carried out by competent tradesmen in accordance with the detailed fitting instructions supplied with every unit and in accordance with water regulations...

Oh what fun, another battle of: it says this; no it says that; or it really means this. :D. First the electrical principles - always a good place to start. So I assume we have an existing 32A radial circuit. We now wish to connect cooking appliances with a total load of 6600 + 2400 =...

You would only get one if first fault had already earth referenced the system. It is accepted that in very small installations this is unlikely. The best use of this is for a single item such as a power tool. The food van can be stretching things a bit. Still the next time you visit the...

For the benefit of those without a copy - the second paragraph of 18.2.5 says: It is accepted that small single-phase generators can run satisfactorily as floating systems, i.e. without the winding connected to the frame or earth. The generator frame and enclosure should be bonded to all...

I said I think we are talking at cross purposes here don't you.

If the frame is connected to the centre tap on the winding - as it often is on small generators - you will short circuit half the winding if you earth one of the outers (what you are calling a neutral) Try it - the generators are quite cheap these days :D.

With a centre tapped system that is floating with respect to true earth an RCD can provide protection but not against shocks to true earth. The exposed-conductive-parts of the installation (food van) are connected as usual to the earth terminal of the generator. Any faults within the...

If it is centre tapped you must not connect neutral and earth together - you will short circuit half of the winding.

Many small generators have a centre tapped secondary winding with a mid point earth. The supply is taken between the outer conductors (neither of these is a real neutral). These generators are often operated as IT systems, and are often floating with respect to earth. This is OK on small...

The European plug and socket project ran for around 25 years - they finally gave up when a prototype was rejected by one member state because it had shutters! I believe that country now requires shutters - the mind boggles - don't go there, it ended in tears last time they tried it :D

14. Where indoor wires are put out of sight, as beneath flooring, they should be thoroughly protected from mechanical injury, and their position should be indicated. Seem like only yesterday - circa 1st Edition 1883 :D

Pliers are OK - anything that just takes the bur off will do. Try this http://indoors.pricegrabber.co.uk/power-tools-accessories/HB3-Pipe-Reamer-10-34mm/m711677054.html

You might find one listed as a conduit reamer - it is just a large tapered reamer. They are likely to be expensive - if it is just for occasional use a large round or half round file is OK.