Latest Discussions : Electrical & Lighting

04:28PM | 09/12/02

Member Since: 05/24/02
8 lifetime posts

Why is the "hot" wire hot when the switch is off?

OUCH! Our bathroom fan was condensation damaged (non-insulated duct in Wisconsin=bad idea). So, I bought new ducting (insulated) and another fan unit (same type). While the wall switch was off, I instaled the unit in the attic. I accidentally (with the screwdriver) made the black (hot) wire and the green (ground) wire complete a connection. [I should also mention that my finger was part of the completed circuit.] Got quite a surprise shock. I looked at the switch and it is most confusing, as there is no ground wire to be seen and both of the wires to the switch are black. Undiscernable hot/neutral wiring is common in "this old house." They both appear black in almost every switch and junction box I have examined. But, in all previous installations of such things as dimmer switches and ceiling fans, if I've marked and followed the previous owner's/original electrician's wiring assumptions, I've never been "burned." I.E.: his "black-to black" becomes my "black-to-black" and his "black-to-white" becomes my "black-to-white." Where would be the most likely place that the neutral and the ground were crossed, assuming that this is the reason I got shocked? What is the easiest way to determine this? What tools would I need? Should I seek professional help (for the electrical problem, that is

kellyyouse

07:20PM | 09/12/02

Member Since: 09/11/02
78 lifetime posts

What always reassures me when doing wiring is shutting off the main power at the circuit breaker to the whole house. That way, there's no little surprises. Also, I would recommend buying some electrical testing tools, namely, a continuity tester (for switches), and a general electrical tester (mainly for outlets). Both can tell you if power is running and help determine which are "hot" wires. These testers are relatively inexpensive (both under $5 a piece at Home Depot).

I also highly recommend Black & Decker's "Complete Guide to Home Wiring." It's so well-explained, it makes me feel like an electrician

Hope this helps!
Kelly

BobF

08:30AM | 09/15/02

Member Since: 10/19/98
223 lifetime posts

Depends in part on whether the the switch is before the light or after the light. Sounds like the switch is after the light, ie) power goes to the light then to the switch. In this case the black is always hot and the white from the switch is also hot, but controlled by the switch.

The other part of this is whether the person who wired the switch and light knew what they were doing.

Never take a chance. Always kill the power at the breaker before doing any electrical work.

The book is an excellent reference.

JimB

05:38PM | 09/15/02

Member Since: 09/09/02
7 lifetime posts

Hello Chaz,

If we asked enough questions about your situation, we could probably determine exactly what happened, but with the information so far, it is impossible to tell for certain.

One possiblility is that the electrician that wired the house used a switch leg to control the fan. In this case, one of the black wires in the fan would ALWAYS be hot unless the breaker is turned off. There would be no neutral in the switch box, only one always hot wire and one switched hot wire.

Regardless of what happened there, please remember that there is no substitute for safe wiring practices. Electricity is dangerous and many many people have been electrocuted when the "switch was off". If you are going to be performing your own electrical work, you should purchase a meter and/or other test devices to check the circuits you are working on. Some of these are very inexpensive and they will pay for themselves very quickly.

For simple wiring and testing, this board and others like it are a great place to ask questions, but remember your limitations and if you aren't sure about something, call an electrician.

Cheers

chazb1

08:05PM | 09/16/02

Member Since: 05/24/02
8 lifetime posts

Kellyyouse
BobF
JimB
JUST WANTED TO SAY THANKS FOR ALL OF YOUR HELP!!! (And, yes, the book is a great reference.)