Q&A: Ask an expert: New plug, socket configuration for SA

September 8th, 2014, Published in Articles: Vector

 

In 2013, SANS 10142-1 identified SANS 164-2 as the preferred standard for plugs and socket systems and it is now expected that this configuration will be phased in on new installations. Vector‘s Peter Adams talks to Crabtree Electrical about the new configuration.

Picture-017Are our current plugs and sockets illegal?

No, the traditional three-pin 16 A plugs and sockets we have used for decades will still be legal for the foreseeable future. It would be impracticable to try and replace them in less than a generation or even longer than that.

So, what should the electrical contractor do when faced with a new installation?

The contractor should consider installing “dual” electrical sockets in all new installations. These are sockets that include some “old pattern” 16 A sockets and some “new pattern” three-pin sockets.

What if the customer insists on having old-pattern sockets installed?

Obviously, the contractor must take his customer’s wishes into account. At this stage, the new pattern sockets are the “preferred” standard, they are not compulsory.

Why is the standard being changed?

There are several reasons. One of them is safety. Our old plugs and sockets are not completely safe – it is possible to touch the live electrode pins as the plug is pushed into the socket or pulled out.

And the socket openings are large – big enough for little fingers to be pushed into them. That makes them dangerous.

Aren’t there shutters preventing fingers or other objects from being pushed in?

Yes, but inquisitive children often find ways to open the shutters by using a pencil or something else. And the shutter mechanisms in some lesser-quality sockets sometimes stick or break, and frustrated home-owners just find a way to remove the shutters.

What features make the new sockets and plugs safer?

First, the sockets are recessed so the pins on the plug are screened as the plug is inserted or removed. Secondly, the shutter mechanism is different – both current-carrying pins must be pushed into the socket at the same time before the shutters open. As far as the plug is concerned, the live pins are insulated for more than half of their visible length. At no time is there any live metal exposed while the plugs are being inserted or removed.

The pins are smaller. Can they carry 16 A?

Yes. The pins on our old plugs were significantly over-designed. As with many other systems, designers erred on the side of extra security and made everything bigger and heavier than necessary.

The old-pattern plugs could carry up to 40 A without problems, even though they are rated for a maximum of 16 A.

Does this mean that even heavy appliances like washing machines and resistance heaters will use the new plugs?

Yes. The new plug might seem small but it is perfectly capable of handling 16 A consistently throughout a full work-cycle of any feasible length. But when appliances will come with them fitted as standard is a different question. The situation is one of supply and demand – when demand increases, then so will supply.

The plug’s cable-entry is smaller. Can you get three-core cable into it?

The pins are designed to take 1,5 mm conductors, which is adequate for this strength of current. There is a cable-grip in each plug and the cable goes into the pin at a right angle, making it harder to wrench the cable out of the plug. And the plug-top design resists any pull on the cable, so it is unlikely to be wrenched out of the socket.

Apart from safety, what are other benefits?

Economy is a big advantage. The old pattern system uses about 70 mg of metal in the pins and sockets, as compared to just 15 mg in the new one. This is important, particularly as the country is facing a major upsurge in building activities as millions of new homes are being promised.

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