LAST time around we only started scratching the surface with regard to ‘conductors'.
And it wasn't about conductors of the ‘transport' or ‘musical' kind...
If you took the trouble to try and figure out why I said there are some 23 definitions in this category, you would have noticed that conductors in SANS 10142-1 come in many guises. Fact is, it can be a length of thin round copper, some would call wire, others again would call the same thing cable, and yet more people would call it a conductor.
You also get flat conductors - not one that has been run over by a bus (with an engine and wheels), but ‘bus' as in busbar - that length of flat copper you find in a distribution board used to connect common live, neutral or earth conductors or cables to - you know as in a piece of copper or aluminium busbar.
Another flat conductor can be a piece of tin or sheet metal - such as the material that could be used to manufacture a distribution board or other electrical box or enclosure.
So let us try to get all this ambiguity sorted out, one way or another.
One thing to remember is that no two electricians will necessarily refer to the same item or thing by exactly the same name or terminology - and this can create confusion for many people. Therefore, instead of rushing into something, think carefully of what it is that you have been requested to do, or to install... and be practical.
If someone asks you to install a piece of conductor between point ‘A' and point ‘B', consider for a moment what would be the best way to go. Would you use soft, floppy thin stranded wire or cable (some call it ‘panel wire' or ‘welding cable'), flexible but fairly rigid wire or cable (some call it ‘house wire' or ‘hard drawn single core cable') or very rigid, near rock solid bar (some call it ‘busbar' or ‘solid core cable').
The funny thing is, not even the authors of SANS 10142-1 can make up their minds about when something is a conductor and when that exact same thing is a cable.
Why does SANS 10142-1 talk about aerial conductor and earth continuity conductor and not aerial cable or earth continuity cable? After all, both those items can also conform 100% to the definition for ‘cable' as defined in Clause 3.9 of SANS 10142.
Let's attempt to list the definitions chronologically instead of alphabetically so as to try and create a clearer picture.
Broad classification of conductors
3.15: conductor: material that is capable of conducting electric current.
3.14: conductive part: any part that is capable of conducting electric current.
On their own, it is a little difficult to picture the need for the distinction, but in the sub classifications it becomes more practical.
We can group the above into sub categories:
3.15.1: aerial conductor: conductor that is supported above the ground and that is (or its insulation is) exposed direct to the open air. (See also SANS 1418-1 (SABS 1418-1)).
An example can be bare or insulated ‘overheads' as it is commonly known, or Aerial Bundle Conductor (ABC) that is used extensively in low-cost reticulation and distribution.
3.15.2: bonding conductor: conductor, including any clamp or terminal, that connects together exposed conductive parts (see 3.14.1), extraneous conductive parts (see 3.14.2) or both exposed and extraneous conductive parts, with the object of bringing such parts to the same electrical potential.
An example is that piece of 2.5 house wire or copper strap you use to ‘bond' the metal hot and cold water pipes to a geyser element earth terminal.
3.15.4: earth continuity conductor: earthing conductor: conductor, including any clamp or terminal, that connects the consumer's earth terminal to the exposed conductive parts of an installation for the purpose of earthing such parts and carrying fault currents.
This is that piece of bare or green/yellow wire or cable connecting your socket outlet earth pin back to the earth bar in the distribution board.
3.14.1: exposed conductive part: conductive part that a) can easily be touched, and b) is not a live part under normal conditions, but can become live under fault conditions.
Examples include plug and light switch covers, metal conduit, distribution boards and other boxes. In other words, these items are part of the electrical installation and are designed to be part of the installation from the get go and are open to touch under normal operating conditions.
3.14.2: extraneous conductive part: conductive part that does not form part of the electrical installation
NOTE: Examples of extraneous conductive parts are a) structural metalwork of a building, b) items such as heating tubes and non-electrical apparatus electrically connected to them such as radiators and gas-fired or coal-fired cooking appliances, and c) floors or walls made of conductive material.
These parts were never intended to be part of the electrical installation but come into contact with the electrical installation sort of by default. A more common way for me to think of it is the copper water pipes connecting the geyser and the taps, for instance.
Similar to the exposed conductive part above but (and this is a very big but...) the metal water pipes were never intended to be part of the electrical installation or to conduct electricity, and because the geyser has an electric element and a metal tank, if something goes wrong on the electrical side, the pipes can become live.
Next month we will delve a little into cables and the obscure use of the word ‘functional'.