Help Please...grounding & completed circuit question

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  #1  
Old 01-06-07, 04:35 PM
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Help Please...grounding & completed circuit question

The majority of my house is wired with BX cable (the wire with the metal jacket surounding it?). I noticed that if I place a tester on a hot lead and the other on the metal switch box (the whites are already connected inside the box) I complete a circuit. Is this normal?

I just set up a junction box conecting the BX cable that was attached to a switch, with a new switch connected with Romex. I attached the ground on the Romex to a switch and then attached the ground to the junction box. The circuit breaker popped. I then used my tester and touched the box itself and the ground leading from the swith and ended up with a completed circuit. Is this usual or am I or the previous owners done something wrong> Thanks in advance for responding
 
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Old 01-06-07, 04:40 PM
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Try again, I'm not sure what your asking.
 
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Old 01-06-07, 04:42 PM
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I would like to know what you are calling a "complete" ckt? you should get voltage to ground if you are testing a hot to ground (assuming 200VAC setting) this does not imply a complete ckt. this implies voltage, it will hurt.

The ground wire should be attached to the switch on the green screw (not another) and your "hot"and "switch leg" should be attached to the two remaing screws...

If your breaker trips it means that you have a ground coming in contact with a "hot" search the circuit and you will probably find it (the ground) leaning up against another switch terminal screw.
 
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Old 01-06-07, 05:00 PM
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" I noticed that if I place a tester on a hot lead and the other on the metal switch box (the whites are already connected inside the box) I complete a circuit. Is this normal?"

yes

the other part; you have me confused as to what you did.

The sheathing on BX (if it is actually BX as in old style and not AC or MC cable) does act as a ground although it is not acceptable as a ground. Newer cables use a green ground conductor that old BX did not have.

So, anytime you contact a ground and another point of ground, you will have a complete circuit, although not a hot one (or at least it shouldn't be)

If you touch any hot circuit and any ground point (which neutral is as well as EGC's) you will also have a complete circuit and it will be hot (obviously).
 
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Old 01-06-07, 05:19 PM
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I suspect that you connected a ground wire to one of the switch terminals. This will trip the breaker if the switch is turned on.

If you still don't understand what you have done wrong, please start at the beginning and tell us the whole story.

By the way, if this is in fact old style BX cable with no ground then you cannot extend this circuit by attaching NM cable (what you called Romex) to it.
 
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Old 01-06-07, 09:21 PM
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Does it have a very thing bonding strip running thro it?
 
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Old 01-06-07, 09:42 PM
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Thanks for the response. The main question is that I believe that something is amis. I set up a junction box to connect the old BX wire, and extend it to a switch using Romex. I hooked up the green ground wire from the switch back to the junction box and attached it to a screw within the box. The circuit breaker turns off. I used my tester and held it against the junction box and the ground coming from the switch and the tester lit up. Does this mean that some how the bx shielding somehow electified the box when attached? Can this be a problem resulting from "upstream" connections?

Thanks again



the other part; you have me confused as to what you did.

The sheathing on BX (if it is actually BX as in old style and not AC or MC cable) does act as a ground although it is not acceptable as a ground. Newer cables use a green ground conductor that old BX did not have.

So, anytime you contact a ground and another point of ground, you will have a complete circuit, although not a hot one (or at least it shouldn't be)

If you touch any hot circuit and any ground point (which neutral is as well as EGC's) you will also have a complete circuit and it will be hot (obviously).[/QUOTE]
 
  #8  
Old 01-06-07, 09:44 PM
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Did you use a redhead? No probbaly not therefore causing a short to the box.
 
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Old 01-06-07, 09:52 PM
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does your tester show continuity? From what you have described, you should show continutity but not voltage. I don't see anyway that you would read voltage the way you are testing. Correct me if I'm wrong but it sounds as if you are simply testing to two very close points on the ground wire or system.

Even if you have voltage on a wire, you won't read it unless you read it to ground.

Explain exactly what wires are attached to what point on the switch and any others that are attached to anything.
 
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Old 01-07-07, 07:31 AM
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the tester that I'm using simply lights up when I usually touch a black & white wire and the circuit breaker is on and no light when off. That said the situation I have is a bit different. I don't know what the situation was before I disconnected the old switch. I needed to extend the original BX wire to set up a new switch accross the room. I installed a junction box and I brought the wire into the box and secured it to the box with the standard metal connector to secure it. I attached black to black, red to red, and white to white. This left the ground from the new romex cable unattached so far in the junction box. On the other end I attached the 3 way switch and also attached the ground wire to the prescribed post on the switch. The light works perfectly. I then placed the cover on the junction box and when the free ground wire touched the box it blew the circuit breaker. If I now touch the tester to the box and the loose ground wire it lights up. If I touch the box and the ground wire I get shocked. How can this occur? I assume it's not right. Could it be coming from the light fixture, another switch etc that's not wired correctly? How dangerous is this?
Thanks again
 
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Old 01-07-07, 08:22 AM
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JOEYRM,

Please do not take this the wrong way, but you should have bought and read a good book on residential wiring before you tried to do any of this yourself. As you and many others have discovered, it is not as easy as it seems when looking at it from the outside.

It sounds to me like you had originally one switch controling a light and you wanted to add a second switch. You ran a three conductor cable with an extra ground from switch box to switch box. Which would be correct.

Your troubles began when you were making the final connections. Correct?

Please go over again what color wires from what cable are attached to what screw in each box. (For example: in the box where the new dead end three way is, you should have attached the black to the darkend terminal on the three way, and the white and red to the two other terminal screws, and the bare ground to the green screw, and pigtailed that wire to the box if it is a metal box.)

I hope I am on the right track. Please post back with all the details so we can help you sort this all out.
 
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Old 01-07-07, 08:26 AM
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Here is a drawing of mine showing a dead end three way.

http://pages.suddenlink.net/jwhite480/3way1.jpg

Grounds are not shown. The ground should be attached to any metal box or green ground screw available. Use pig tails with wire nuts if needed. Do not put more than one ground under one screw.
 
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Old 01-07-07, 10:39 AM
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[QUOTE=jwhite;1103321]JOEYRM,

Please do not take this the wrong way, but you should have bought and read a good book on residential wiring before you tried to do any of this yourself. As you and many others have discovered, it is not as easy as it seems when looking at it from the outside.


Thanks for the response. I am not replacing a single pole switch but I am merely moving a three way switch to a new location. I did read the book and have been doing similar DIY projects in my house for 25+years. This is in my daughters house which was built around the same time as mine and this is the first time I have ever encountered this problem. My assumption is that the previous owner crossed a neutral with a ground somewhere in the past which is causing my current problem. I assume that problem existed prior to my moving the switch. How do I locate the root cause? Switch by switch, outlet by outlet, fixture by fixture exam, or is there an easier way. I'm hoping that if I insulate the ground which will solve the immediate problem that this will not be dangerous. Am I correct?
 
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Old 01-07-07, 10:46 AM
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Is this a dead end three way? Meaning the one that you are removing?
 
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Old 01-07-07, 10:59 AM
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Joe, let me add that I meant no offence. I am basing my statement from what I could guage reading your posts. The internet is a wonderfull think, but sometimes communication can be difficult.

If a neutral and ground were crossed on a branch circuit the breaker would not necessarily trip. It would make for a dangerous situation, and the fact that the breaker might not trip is what makes it even more dangerous.

If we have ever failed to help someone who came to this thread to solve a problem, I for one have not seen them post back to say so. Usually it is the other way around and we get some who come back just to say thanks.

dont give up, we can work this out.
 
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Old 01-07-07, 11:16 AM
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I'm hoping that if I insulate the ground which will solve the immediate problem that this will not be dangerous. Am I correct?
--------------------------------------------------------------------------

No.

The fact there is apparently power on a possibly exposed metal object, it is the proverbial snake waiting to strike.

Since you do not know where the power is coming from, there is no way to determine what may be energized and possibly cause harm.

-------------------

one thing I just realized as well. You spoke of a "free" ground. There should be no free grounds. they should all be connected to another ground somewhere. That is what makes the system work. Now another thing. You can actually connect any neutral to a ground at any point and it will not trip a breaker. they are ultimately connected together in the service. the reason they are seperated in the field is that a neutral is a current carrying conductor and if the ground becomes involved with it outside of the sercive, this makes the ground system current carrying as well. Possibly any point within the grounding system is a shock hazard at that point.
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OK. from re-reading everything, it seems you have the ground (that on the one end shorted out against the box the BX is coming into) is attached ONLY to the ground term of the new switch. Correct? Is the new box steel or plastic? If steel, pull the switch free from the box but leave all wire connections intact. check from ground wire (romex) to the steel box (at old location) What do you have?

suspicion here is that you have a switch that is shorted to ground internally. Other possibility is that if a steel box, you have done as another suggested and shorted a hot to the box at the new location.

----------------------

joey, in support of jwhite and all here. we try to assist all that need it. as jwhite stated, sometimes this type of communication causes problems that are difficult to overcome. if you help us, I can promise you we will do whatever we can to help you. I know jwhite menat no indignation, he is simply trying to help.

If you feel frustrated, just imagine how we (myself a licensed elect, jwhite as well) feel when we know you have a problem and if we were actually there, we would just jump in and check all the things in out heads to determine the problem. What we have to do is ask you (who apparently are not totally without knowledge of the field) to give us info and test things as we would. It takes a lot more time to do it this way and can be frustrating to us because of it.
 
  #17  
Old 01-07-07, 06:18 PM
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No offense taken. Thanks to all for their help. I finally called my electrician as this was the first time I encountered this problem and left it in his hands. My daughter just moved into this house and we need to figure out all of the junk that the previous owners did. Thanks again. It won't be the last time that I ask for help
 
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