Tuesday, 31 December 2013

Shoddy Workmanship Results in Burnt Electrical Plug

Season's Greetings and Happy New Year.

This time I won't be ranting about the scheiss of the IT industry. Instead, I'm going to relate to you a real problem I've noticed with a widely available electrical accessories some of which are OK, whilst others downright shoddy.

Life is so convenient these days, three-in-one instant coffee packages with coffee powder, sugar and creamer premixed and sold in packets (no wonder Malaysia has the highest incidence of diabetes in the region), ready-assembled printer cables, prefabricated computer power cords and so on.

The day before yesterday, my cousin passed me a ready-assembled extension power bar to inspect and see what I could do about it. Part of the plug attached to it had melted, presumably after it was used it to power something which drew a high current.

Now here's a picture of the plug. Click on it to view it in full size.

Opening it up revealed that there was a small fire inside by the live pin, which had blackened the fuse. Lucky the fire was contained and did not spread. (See below)

Taking it apart revealed that the copper part of the brown coloured live wire had melted, as can is evident from the beads of molten copper in the wire hole in the live pin where it was connected.

Such high temperatures under heavy load could only be generated either by insufficiently tight fastening with the screw, too thin an amount of copper wire secured bythe screw, the wire merely touching the connector of the live pin or a wire which had broken and was just touching the other part secured by the screw.

Such wiring connections will not show any problems under light electrical loads, such as notebook PCs, mobile phone chargers, video, audio equipment and even TVs but power a high current device from it, such as a washing machine, kettle or vacuum cleaner and the loose point of contact will get very hot due to high contact resistance.

Remember the power equation, Power = Current squared x Resistance
or P = I squared X R.

If resistance is large for a given current, then the heat generated at that point will be high.

When fastening electrical conductors together, it's essential to ensure that good contact by the maximum surface area between the two conductors to minimise electical resistance of the area in contact.

To achieve this, first make sure that a thick enough amount of wire is inserted into the hole in the pin and then tighten the screw upon it firmly to ensure a good contact  between a maximum surface area.

Opening up the connector side of the power bar revealed that the wires had been shoddily fastened to the terminals. This is apparent from how the blue neutral wire was secured in the terminal. (see below)

Removing the cord grip also revealed how shoddily the green and yellow earth wire was fastened, with a long amount of exposed earth wire protruding from the connection point.

Unfortunately, such shoddy workmanship is pretty common with these ready-assembled power bars.

Such problems also happen with ready-moulded notebook PC power cords, like the one which came with my Hewlett-Packard notebook PC, in which the internal connection came apart so the notebook could not charge. Fortunately, it was a standard type of power cord, so I could buy a replacement from a computer shop.

However, my friend bought a similar notebook PC power cord which grew hot and melted a part of the plastic socket which fits into the mains power adaptor.

He had bought a cheap, China-made power cord and ended up with such problems. So don't be penny-wise, pound-foolish when buying such electrical items, since in the worst case, it could even kill you or your loved ones.

Another thing to note is that the power cord is firmly secured by the cord grip in plugs and power bars. Firmly securing the cord (i.e. the plastic or fabric sheath of the electrical cable) is very important, since the cable will inevitably be tugged under normal use and if the cord is not firmly secured by the cord grip, the strain will be on wires at their point of connection in the plug and not on the cord, which can lead to the wire breaking inside the plug.

For the same reason, this is why you should pull a power cord out of a PC's power adaptor by holding its plastic connector part and not pulling on the cable, as this can eventually result in an internal disconnection.

Below is an example of a plug previously attached to a ready-assembled power bar where the right nylon leaf of the cord grip had been removed by the assembler, who must have found it too hard or was too lazy to force the cable in between the two leaves, which admittedly is a bit hard to do but very necessary.

The assembler most probably was some smart Alec or ignoramus in doing so, which left the cord effectively ungripped.

However, I lay most of the blame fairly and squarely on his or her management who did not bother to brief their workers and supervisors, and conduct adequate quality control, knowing what cheapskate pariahs most Malaysian managements are, with their mentality of competing on the lowest price and cost cutting, whilst ruthlessly exploiting their workers, most of whom are foreign.

Many power bars in the market are also shoddily constructed like the one below, which bears a SIRIM (Standard and Industrial Research Institute of Malaysia) quality assurance stamp to boot.

After some use, some of the switches on this power bar came off, exposing dangerous live contacts which can kill a person who touches them.

As an interim measure, I had taped over one of the exposed broken switches but others came off later.

I won't just throw this power bar away, since someone may pick it up and use it. Instead, I will either dismantle this power bar and remove the copper and plastic for recycling or just smash it with a hammer before disposing of it

However, I can re-used the power cord with attached plug with a good power bar.

With such pariah cheapskate attitudes amongst Malaysian managements with simple, low-tech, screwdriver assembled items such as power bars, such attitudes will carry over into highly sophisticated products such as Malaysian made IT equipment and software.

If this third world mentality is allowed to continue, I see no way that Malaysia will ever achieve developed nation status by the year 2020, whatever bullshit and ballyhoo our leaders and ministers throw at us, via their spin doctors and a gullible, subservient media.

Below is an example of how a plug should be properly wired up. It's only plugged into the power bar to hold it in place for photography. The power bar is not plugged into the mains.

The plug used here is a rather pricey one by the British firm MK, which most probably has a patent on this unique design, since I've not seen it in any other plug brand.

Here the screw sticks up from the connection points and the copper wire is wrapped clockwise around the screw.

The brass nut with a circular washer (shown removed for illustration) is tightened clockwise onto the wire, with the washer pressing down on the wire, making tight contact between wire and pin over a wider surface area than for most other plug designs.

Why wrap the wire clockwise? Well the nut is tightened by turning it clockwise, so the wire should also be wrapped clockwise around the threaded screw post to be in harmony with the direction of rotation of the nut.

 Also, note that the cord is firmly secured between the two leaves of the cord grip.

When I was a computer service engineer, installing and maintaining refrigerator sized mini computers and filing cabinet sized hard disk drives, I used such MK plugs for all our computer equipment.

No. This isn't an advertisement for MK but an expression of my appreciation for its innovative design which has made it a world class brand.

This article is primarily for the benefit of consumers, though hopefully some more enlightened Malaysian managements reading this will also take note of the importance of electrical best practices and of good product design.

It's not rocket science but simple common sense, even with seemingly "unsexy" things such as electrical power bars and plugs, but such best practices are the foundation of more sophisticated, higher value products.

Remember that a strong foundation is the most important part of a building, since the most architectually sophisticated building with a gee whiz smart building system, bio-climatic yada, yada, yada design can still come tumbling down upon its occupants if the foundation is weak.



  1. Yikes! I feel your pain. I used to live in a really old home with poor electrical devices. Many of the electrical sockets in the wall had burned out and broken electrical contacts and other electrical parts that kept it from working right. I had some cords melt as well. I get that companies want to be cheap, but I'd rather pay more for a better made product then to have something cheap that melts. That's just dangerous!

  2. Amazing really how simple it can be to communicate with people and have them understand a certain topic of burnt electrical plug, you made my day.

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  6. Hi everyone,

    Apologies for my ver late response.

    Thanks for your kind comments.

    I hope this will help improve the situation with power bars somewhat, even though I don't expect it will change the world.

    I hope this