Electrical earth leakage at computer housing

Electrical earth leakage at computer housing

Since I moved into my current house, I had on many occasions, received complains from my visitors, and sometimes I myself, that there was a small electric tingling shock whenever any one of us touched the steel housing of the computer body. These happened on several different occasions, leading me to think that it might be related to static electricity whenever the atmospheric condition was right for this. Reading up from forums on the internet, I found that many of them blamed this on static electricity.

Electrical earth leakage at Air Conditioning socket

Electrical earth leakage at Air Conditioning socket

Not totally convinced from the discussions, I had opened up my computer to check the wiring, and had found that every connection was proper and there were no loose connections that would give out any tiny electrical leak to the body of the computer.

Original power socket

Original power socket. Note the yellow wire and the blackish green wire.

This went on for some time without causing me any concern, until the day my air conditioning unit was not functioning well and I had to check it out. I found that the air conditioning outdoor condenser unit was also giving me a slight electrical shock when I touched the steel body. I could not service the unit myself, other than cleaning up some air filters, because I did not have all the tools and equipment for this. So I called in the service men.

Electrical switchboard

Electrical switchboard

The air conditioning technicians had to use a piece of cloth to insulate themselves from the electrical shock when they dismantled/connected the freon gas inlet in order to charge the refrigerant gas into the system. That was when I decided that this was a real problem. Something was not right with the wiring of this house.

electric light bulb tester

Electric light bulb tester

After talking with a contractor, I managed to extract some information from him regarding the malpractices of some people in his line of work. Opening up the electrical power socket and observing the wires there confirmed my worst fears. There was a yellow wire connected to a white wire at the same live connector terminal of the socket, and a green wire connected to the black wire at the neutral terminal. And there was only one green wire at the earth connector terminal.

Electric distribution map color coded

Electric distribution map color coded

Well, I was not very well versed in house electrical wiring, but I could sense that this was definitely not right. The wiring contractor did mention that sometimes in their desperate need to finish a job, and when they were faced with a situation where the concealed wiring embedded in a concrete wall did not conduct (meaning that there was a break somewhere inside the wall), they might use an earth wire as a neutral wire, just to make it work. Alarming, but true.

Electrical distribution floor plan

Electrical distribution floor plan

In order to fully understand how the wiring was laid, I read up from a DIY book, and also studied the house switchboard. What I discovered was more unapproved wiring connections. There was a bathroom heater which was added in, connected on externally laid pvc 3-core wiring. But the most important thing I wanted to establish was whether I could switch off the power for the house/circuit that I wanted to dismantle. Well, since I was already doing this, I decided to do a complete distribution map for all the electrical outlets for the whole house.

What I did was this: I made a rough sketch of the switchboard and switched on all the lights and power socket points for the whole house. I had also prepared a simple tester tool consisting of an electric light bulb wired to a plug. This tool was used to test whether a socket had any electrical supply when plugged in. I identified each of the switches by numbering them from 1 to 7. When I switched off each of the main switches individually, and then observing which equipment/light was turned off, I could determine which switch controlled which area. From this exercise, I managed to make a map of the electrical distribution for the whole house. I used color crayons to mark the different areas for easier reference during the testing.

After much thought, I deduced that somebody (the previous tenant/contractor) had accidentally cut the wire in the wall, or had found that the wire was not long enough to connect to the required socket, so they had connected a yellow wire to the white wire, now embedded in the concrete wall, and similarly, a green wire to the black in order to extend the length to make the socket work. But he forgot or did not have enough green wire to connect to the green wire of the socket. The white, black and green wires which were already connected to the socket were to loop to another different socket in the house. (at least the green wire was suspected to be going to the air conditioning unit socket) With this in mind, the options I had were:

  1. To lay a completely new white, black and green wires from the switchboard direct to the offending socket
  2. To still use the existing yellow and green wire for live and neutral and lay a new earth wire from the switchboard to the offending socket
  3. To adopt item 2 above, but connect another earth wire from the nearest place, in this case it was a lighting circuit earth wire still sticking out of the wall.

I opted for the 3rd choice as it was the easiest.

So I tested the theory out. (See the video below) I found a long wire and connected it temporarily using crocodile clips from the earth wire of a lighting circuit and attached it to the power socket earth connector in question. The electrical leak was found to have disappeared. My theory worked. Somehow the stray charges had been conducted to the earth of the building and were no longer present.

After that, it was a relatively simple matter to make a proper connection using a new earth wire and covering them up inside a casing for a more pleasant appearance.

So the electrical leak from my computer had been eliminated. Note: The stray electrical leak was confirmed to be from the computer. This phenomenon manifested itself only when the earthing of the house was not present.