I am redoing the bath in a 1950's home and have discovered while wiring for new light fixtures and switches that even with breaker switched off a small amount of current is present. Is this a bad breaker or did I wire something wrong? Thanks!

 

There are several situations in which voltage or current may be detected on a circuit that is nominally 'off'. Some of these situations indicate a problem with the circuit, others are part of normal operation, and others are part of normal operation but can be extremely dangerous when you are working on the circuit.

Why don't you describe how you determined that there was current present. Did you feel a shock from a wire? Did you get an indication on a neon tester? A digital volt meter?

If you were shocked, was it by a 'hot' (black) wire, or by a 'neutral' (white) wire?

Do you know if the same cable is share between multiple circuits? Are there multiple breakers that seem to feed through a single junction box near where you were working?

Can you describe the junction box (number of wires, colors, etc.) that you were working in when you detected current?

-Jon

 

winnie...I discovered the problem while "tying" into an existing line. In other words adding a switch and light fixture to a circuit. I turned off the breaker for that "line" and tied into it. As I was handling the nuetral (white) wire I felt a very small tingle or current. I went ahead and completed the wiring and tested the switch and fixture wires using a test light. The light showed power that looked normal with the breaker back on and a dim light even with the switch turned off. So it seems that with the breaker off or on there is a small amount of current on the nuetral wire. Hope that explains it well enough, thanks.

 

If the neutral wire is shared, as in a multiwire branch circuit it can carry current if only one of the circuits is turned off. In a multiwire circuit two hots from different phases are used with one common neutral. The theory is that the opposite phases balance the load on the neutral therefore it is not overloaded. however if only one of the shared circuits id turned off the other circuit is still providing power to the neutral and poses a shock hazzard as you have discovered.

 

Okay, I have some of the picture. First I have to shout at you:
IF YOU EVER GET A 'TINGLE' OF ELECTRICITY FROM A CIRCUIT THAT YOU ARE WORKING ON, __STOP__. FIGURE OUT WHAT YOU NEED TO DO TO SHUT OF __ALL__ POWER TO THE CIRCUIT.

If necessary to restore a safe situation, shut of the main breaker to your house. Depending upon the cause of the 'tingle', you could very suddenly and unexpectedly find _lethal_ voltage present on the wires. Electricity is not a game, and poor safety procedures will get you injured or killed. If in your DIY work you encounter something that you don't understand, then take the time to figure out the situation, or bite the bullet and hire professional help.

The above said, I believe that this is a situation which you _can_ figure out. It may simply be that you will better understand your house electrical system and be better able to work safely on it in the future. It might even be that you will discover a serious problem prior to its causing damage.

You will need to correctly understand the concept of current. What you called a current measurement was a voltage measurement. Current is a measure of the electrons flowing through the wire, voltage is a measure of the force that pushes electrons from one place to another. You don't get a shock from a wire; instead you get a shock from _two_ conductors and the voltage between them, eg a wire and the grounded metal box or the wire and a grounded pipe.

If the neutral wire that you were testing showed significant voltage, then it is not properly connected back to the panel. The voltage on the neutral wire, relative to ground, should be less than about 3V when the circuit is under full load. If the voltage on the neutral wire is greater than this, then it suggests a high resistance connection somewhere in the wire back to the panel. If the neutral wire that you got the shock from had been _disconnected_ from the return to the panel, than a high voltage could be expected; clearly there was an open connection back to the panel. So if with all the wires connected properly there is still high voltage on the neutral wire, then you have a problem which needs investigation.

As you noted, you got your shock from the _neutral_ wire on the circuit. Rather than meaning that current is somehow 'leaking' through the open breaker, this suggests that a _different_ circuit is sharing that neutral. What you need to do is figure out what other circuit is sharing the neutral. Do this by turning off _other_ circuit breakers in the panel until you no longer detect voltage on the neutral that you are working on.

The most common _correct_ way for a neutral to be shared is in a 'multi-wire' circuit, with two hots from _opposite_ bus bars in your circuit breaker panel, and a single neutral. This is often done with a single cable that has a black wire, a white wire, a _red_ wire and a bare or green wire. The white is neutral, and the green is ground, and _both_ the black and red wires are hot. In such a circuit, if you do not turn off _both_ circuit breakers, then you can have current flowing through the neutral wire. As I noted above, the voltage on the neutral wire is low until you open the circuit. So with a multi-wire circuit you can have no detectable voltage until you separate a couple of wires, and then suddenly get a lethal shock. You should figure out if there are any multiwire circuits in your house, and mark them so that you know to turn off _both_ circuit breakers when working on the circuit.

The most common _incorrect_ way for a neutral to be shared is a 'bootleg' neutral. In this case, a load (say a lamp) is connected to the hot from some other circuit and the neutral from the circuit in question. If this happens, you can again get surprising shocks, and you can also overload the neutral.

Another possible problem is a 'neutral-ground' fault where the neutral is connected to ground at some point other than the panel. If you have a couple of 'bootleg grounds' from different circuits, then these connections to ground can provide a path for current to flow between circuits. This can be a serious problem, and can present a heating or shock hazard.

If you can still measure the neutral voltage without opening things up, I'd suggest turning off breakers until the voltage goes away. If the voltage goes away when an _adjacent_ breaker is turned off, then you have a multiwire circuit. If the voltage is > 3V, then you should investigate things further; do any lights get _brighter_ when large loads are turned on, for example? If the voltage only goes away when an unassociated breaker is turned off, or worse if _several_ breakers need to be turned off to make the voltage go away, then you have serious problems which need looking into.

-Jon

 

i also had a leaking breaker.

the circuit in question was a standard bedroom circuit. but we also have one leg of a surge protector on the breaker. the other leg goes to the breaker above to protect the other leg of the service panel

i disconnected the protector and all current was gone.

the surge protector was replaced but again a very small current flowed.

i have to think the design of the surge protector allows some current to flow into the switched off breaker. (i hope)

our house is almost new and there are no multiwired circuits etc.

the panel box does have a handful of the twin skinny breakers

 

diyguy.

Your surgeprotector should be on a two pole breaker(for this exact reason) not two single pole. that is why you felt the tingle.

 

sparky-lu 697

thanks

i'll let my lightning rod install know about this