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Understanding the definitions in Clause 3 of SANS 10142-1 - Part 3

LAST month we looked at the limits of the electrical installation as per the definitions of SANS 10142 and, hopefully, the illustration cleared up some confusing issues and statements by people who do not fully understand the definition.

Although the final word was a bit simplistic perhaps, if you apply your mind you should have no trouble in defining the exact limits of the installation you test and for which you issue a Certificate of Compliance.
It is sad to see how many so called ‘inspectors' (or contractors, electricians and ‘consultants') deliberately twist the facts and make loads of money out of the unsuspecting public.

Sometimes an ill-informed ‘inspector' can cost the public unnecessary money by demanding a rewire of old wiring for instance, whereas if he knew the code, the way he should, that expense would not have been incurred.

This is something that has bothered me for years! And, no matter how hard I try to get the message across, there always seem to be someone out there, who sees a gap and applies unscrupulous tactics to put money in their pocket...

Okay, so let us explore further - at least we now have a clear framework within which to operate...

Between the ‘beginning' and the ‘end' of an electrical installation there are quite a few definitions that make up that installation, as you might have noticed since we started looking more closely at Clause 3 of SANS 10142-1.

And so, to continue...

3.2 Accessible ‘not permanently closed in by the structure or surface(s) of the premises'

The above statement simply states that if something has a lid - elbow, ‘T', two-way round box, etc, that is designed to be opened and closed (with or without screws) and if items where cables or wiring can make a 90 degree turn in mid air, such as draw boxes, trays, trunking etc - it shall be accessible at all times.

I must be able to easily access it and open the lid (however it is fixed in place) and be able to manipulate the wiring for faultfinding or repair.

This means you will not plaster it closed; you will not install it in a ceiling space where you will never be able to access again after completing the job, nor behind a built-in cupboard, and so on.

Another ill-understood definition is that of the appliance. Even though the appliance does not form part of the installation, there are definite do's and don'ts when it comes to connecting them to the electrical supply.

Let's have a look...

3.4 Appliance ‘machine, tool, device or instrument that is operated by electricity for the purpose of doing work, or for providing heat, light or motion, or in which electrical energy is modified into another form of energy'

The first part of the above definition up to the word ‘or' is actually repeated in the rest of the sentence.

Why do I say that? Simply because taking electricity and providing heat for instance, is exactly the same as taking electricity and modifying it into another form of energy - what else is a heater doing other than taking electrical energy and turning it into heat energy?

Anyway, what these guys want me to understand is that a drilling machine, grinder, washing machine, stove, a pool or any other pump and a ceiling fan are all appliances in terms of the definition.

Now because of this, and depending on the construction or method of installation, I have to treat each appliance on its own merit when it comes to installing these in or on premises and connecting them to the electricity supply.

To be able to do this, I have to ‘classify' the appliances into various ‘categories' if you like. Formulate a set of rules for each of these ‘categories' and then install these or treat these appliances according to those rules.

To begin, you get the following ‘category':

3.4.1 Class I appliance ‘appliance that has at least basic insulation throughout, and that is provided with an earthing terminal or earthing contact and is designed (in the case of single phase) for connection by means of a three-core flexible cord'

The key words here are that there are provisions for earthing - terminal, contact etc.

You do not have to be a rocket scientist to figure out that the above is describing a kettle or electric urn, for instance. Firstly, it is made of metal. The electrical bits are insulated from the rest of the appliance. It is provided with an earth terminal and flexible cord is used to connect it to a socket outlet that has an earthing contact.

But then a geyser... What about a geyser? Or a stove for that matter? These are not normally connected to the supply via a flexible cord, but they also fully comply with the definition of a ‘class I appliance'.

The second main ‘category' of appliances is:

3.4.2 Class II appliance ‘appliance that has double insulation or reinforced insulation (or both)
throughout, and that is without provision for earthing'

The key words here are: without provision for earthing - no earth terminal, contact etc.
Here the standard describes a handheld hairdrier, food mixer or electric shaver perhaps. And, as you know, these appliances normally come with a cord and plug with only two pins.

Next month we'll look at some more sub categories and put this whole appliance thing into perspective.

What appliance would you like for Christmas?