Background:
My home has two-wire electrical boxes, hot and neutral, there is no ground wire running to any of the wall boxes or wall switches. The house is 50 years old, the wiring is insulated with some cloth like stuff jacketed around the two wires. The wire appears to be in good shape throughout the house.
Problem:
While adding some lights in a bathroom remodel, I turn off the wall switch that feeds the lights I’m adding, then notice a small tingle sensation when I touch the hot neutral wires. I measure the voltage across hot and neutral and measure about 60Vac. So, why is there a voltage across hot and neutral when the SWITCH IS OPEN ?
Obviously, there is current flowing on neutral which is causing this voltage. What should I do ? Is it because I don’t have a ground ? Shouldn’t the neutral and ground (from the power companies electrical pole) be connected together at the main box ? If their not connected, is this the result ? Can I establish an earth ground 40 feet (in the bathtroom that I’m remodeling) from the main electrical box by connecting to a copper cold water supply going into mother earth ?
Any help is greatly appreciated !!
Replies
please don't work on any circuit unless you turn it off at the service panel! Don't trust that the wall switch was wired properly. Also, especially if you don't know that wiring intimitely (know for sure that it was all run correctly, that is), confirm that the power is off at the device by using a tester before touching any bare wires (experience from seeing enough dangerously mis-wired stuff in my time).
Why does your neutral have 60V when the light switch is off? Probably you've another device that is running (because you did not shut off that circuit at the service panel) and its 'return' current is available on that neutral to energize you any time you present a better ground path than the one that your wiring is providing when you touch it. You can confirm this by shutting off all power/unplugging anything else on that circuit. The potential difference should drop to 0. If it does not then you've got a problem somewhere that must be resolved.
Of course, without more information this is just a guess.
I am not an electrican, but my experience with working on older houses is.......that the feeds to the ceiling lights generally do not come from the switches. The power is feed to the box in the ceiling and a switch leg to the wall switch and back. So when you turn off the switch you still can have power in the ceiling box. Best rule: Turn of the breaker, be safe not toast!
First and foremost, kill the circuit at the fuse or breaker before you do anything. Get one of those proximity sensors -- about the size of a small felt tip pen, about $15 -- and when you open a box, use it to check that there aren't other hot circuits present. If there are, kill them, too.
>. I measure the voltage across hot and neutral and measure about 60Vac. So, why is there a voltage across hot and neutral when the SWITCH IS OPEN ?
> Obviously, there is current flowing on neutral which is causing this voltage.
Not necessarily. What are you using to measure the voltage? If it's a high impedance digital meter, it could be that one point you're touching is grounded, and the other is a piece of wire that's floating, but running parallel to a hot for a considerable distance. This is in effect a capacitor between the floating wire and hot, and you're getting this reading through the capacitance. For power work, you really need a low impedance meter, which you can make from a high impedance meter simply by shunting the input with some resistance, a small incandescent lightbulb will do nicely.
> What should I do ?
Turn it off at the fuse or breaker, trace everything out, and make sure that your switch is between hot and the load, not between neutral and the load. Make sure all connections are tight. Poke around thoroughly with that proximity sensor before you touch anything. If you're not absolutely comfortable and confident in your ability to do the above, get an electrician to do it for you.
> Is it because I don't have a ground ?
Unlikely, unless you mean that there's a piece of wire that should be neutral, but is instead floating because the switch is on the wrong side and the bulbs are out.
> Shouldn't the neutral and ground (from the power companies electrical pole) be connected together at the main box ?
Yes. Connection between neutral and ground is required at the service entrance, and forbidden everywhere else.
> If their not connected, is this the result ?
No, if they're not connected, the danger is that a hot wire contacting a box or conduit will not trip the breaker, but will instead make all the boxes and conduit hot -- a very bad thing.
> Can I establish an earth ground 40 feet (in the bathtroom that I'm remodeling) from the main electrical box by connecting to a copper cold water supply going into mother earth ?
No. This is very dangerous. The electrical ground is required to be connected to the water pipe within 5 feet of where the water line enters the building, and any other connection to the water system is forbidden. If you have current flowing through the water pipes instead of the neutral, and somebody disconnects a pipe, suddenly you have 120 volts between the ends of the pipes. There was a guy on this board who reported getting a really bad shock exactly that way.
It's not impossible to learn enough to do electrical work. There are books you can read. Taunton's "Code Check - Electrical" is an excellent one. You'd also need one of the how-to books. But think very carefully about whether it might be better just to pay an expert to look over the whole system.
-- J.S.
1st: Be careful. Most manuals tell you to turn off the power. Good advice. Unfortunately that usually makes diagnostics nearly impossible. That's why electricians make the big, not so big, money and have high mortality rates.
A loose or corroded connection, possibly at the panel, between the point of measurement and the panel would be a likely cause of the reading on the neutral. If all the connections were good, assuming the run isn't exceptionally long and that the neutral bar is indeed firmly connected to the neutral at the transformer, the reading would be very close to zero.
the faulty connection along with a return current show as the abnormal voltage. Door bell transformers are often overlooked as a source of return current. Quite a few small appliances, radios, TV, etc. commonly maintain a trickle current through the primary coils of their transformers. Unless they are unplugged they are not truly off.
The point made about high impedance meters showing ghost voltages, ones that have no real current behind them, is very true. Florescent ballasts and capacitors and even long parallel runs can induce voltages the look real. Around here the Square D " Wiggy" is the industry standard. I recommend it to anyone making repairs. Being both rugged and reliable it is also largely immune to ghost currents. It doesn't give you a precise voltage but seldom is that a problem as comparative voltages are usually the trick. Get good with one and you will be able to tell voltages by feel.
Consider rewiring. At least have someone qualified look at it. As for the grounding remember: only one connection to the plumbing and that within 5' of the entrance. Also note that without a ground surge arresting equipment won't work. Consider adding a dedicated computer circuit.