Dale's Ramblings

We have a storage space below the stairs in which there is a light bulb. This week the bulb got bumped and the glass separated from the aluminum threaded socket. I crawled in there with some small pliers with which to grab the threaded part and unscrew it. Before I touched it I decided to test to see if the switch was on or off so I applied my voltage tester to the socket and the metal housing - it had 110 Volts. I flipped the light switch and tested again - still 110 Volts !  Swicth - test, switch -  test ,switch -  test - no doubt about it, the thing was live no matter how the switch was set. Wow! if I had touched it with the pliers 110 Volts would have run through my body to the concrete floor below.

So I switched off the power at the main distribution box and tested again, now it was dead and I could unscrew the remains of the light bulb. Screwed in a new light bulb and swithed the circuit on again. The light worked and the switch operated it fine again.

So why was there current when the switch was off? Well the switch only switches one of the wires that run to the light. After switching the electricty off at the main panel again I unscrewed the light fitting to ensure it was proplery grounded. Looked fine. Then I opened up the switch and found that  it was also was grounded OK, but... the white wire was being switched. The white wire is the USA represents the neutral wire. So the live (black) wire was always live at the light socket!

It seemed illogical to me that the outer threaded contact that is easily touched was always live so I did some web searches on the subject. Sure enough there are two errors in the wiring.

1. The live (black) wire is the one that should be switched, not the white neutral.
2. The live (black) wire should be wired to the center contact of the light socket.

I will be rewiring both the switch and the light socket. In fact I will replace the light fitting with one that has a protective cage around the light bulb. i also plan on testing all the other sockets in the house for incorrect wiring! You might want to have your lights checked also.

Most importantly, do not assume that because the switch is off, there is no power at the light socket!