Ground Fault on Internal Circuit without Breaker Trip

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  #1  
Old 06-24-04, 01:29 PM
thompsdw
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Ground Fault on Internal Circuit without Breaker Trip

My daughter told me several days ago that the lights in her bedroom were no longer working. I went to check them and they were working fine. Last night the lights went out again, and it appears that they are out for good this time.

The first thing I did was check the breaker. It was not tripped. I cycled the breaker anyway, however, power was not restored. After I noticed that her entire bedroom circuit was dead (receptacles, lights, etc.), I decided to test one of the receptacles with a tester. It showed a ground fault wiring flaw. I killed the breaker and tested for continuity between the ground and the hot on the receptacle. There was continuity. A GFCI is not installed as a part of this circuit. I unplugged and removed light bulbs to ensure that the ground fault was not coming from outside of the wall circuit. It was not. I am now chasing the fault up what appears to be the hot feed for the room.

What could cause a ground fault without tripping the breaker? I guess the most logical failure would be in a switch (or more likely a receptacle) failing with the breaker not working? The house is only 4 years old, so I am guessing that wiring deterioration is not a high probability. Is there something that I may be overlooking, or other places I should be testing? Can a failed breaker cause this problem back at the box?
 
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Old 06-24-04, 01:31 PM
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Look for a failed backstab connection on one of the receptacle outlets.
 
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Old 06-24-04, 01:42 PM
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I decided to test one of the receptacles with a tester. It showed a ground fault wiring flaw.
What exactly did it say? Did the tester indicate "open ground"? A "hot/ground reverse"? An "open neutral"? I'm not exactly sure what a "ground fault wiring flaw" is.

I killed the breaker and tested for continuity between the ground and the hot on the receptacle. There was continuity.
This test is meaningless. Continuity can be provided by anything connected to the circuit.
 
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Old 06-24-04, 01:59 PM
thompsdw
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More information ............

John,

The tester indicated a hot/ground reverse.

The fact is that I can actually test voltage across the terminals on a light switch when the circuit is on. One side is grounded and one hot. It tests a lower voltage of ~80V AC. All I am saying is that I am flowing to ground through a hot somewhere.

Bob,

Good suggestion. I have found few of the stabbs used, however, there were some used. I plan to replace most all and use the screws.

All,

Are there any other tests that I can run to track down the fault?????

Thanks very much for the quick responses......
 
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Old 06-24-04, 02:12 PM
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Just a suggestion, it may not be "flowing to ground" it may be shorted to the neutral just as easily. The neutral is connected to the ground at the panel, so it should show a continuity there (if it shows a continuity to the ground).

I would unplug everything on this circuit, make sure it is the house wiring and not something that is plugged into it (like a lamp) and try and start breaking up the circuit at each outlet:

clear out all the kids and pets,
shut off the breaker,
undo all the wires at one receptical and wirenut (or cover) them so they are seperated,
turn on the breaker,
test which set of wires is hot,
move to the next receptacle/light-switch and see if it still has power,
repeat until only one set of wires is hot (that is your homerun to the panel)


then work back the other direction, and test the receptacles as you reconnect them. you should find the fault that way unless it is in the middle of a wire and not in a box.
 
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Old 06-24-04, 07:38 PM
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You do not have a ground fault wiring flaw. You don't even have a hot/ground reverse. You have an open neutral. This is a failed connection of a white wire. 98% of the time it is a failed backstab connection of a white wire. Open up every box on the circuit, whether currently working or not, and reterminate all white wires from the backstab holes to the adjacent screws.

This is not a guess. I've seen this problem hundreds of times. Shut off the breaker and get started.

P.S. Once you get this fixed, I'll explain to you all those symptoms you are currently seeing if you are interested.
 
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Old 06-24-04, 09:16 PM
thompsdw
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Thanks for the Posts!!!!!!

Thanks for the info. I spent most of the night mapping out the circuit and now know how electricity flows. We are going through every box. I will check the neutrals in each box. I guess that would explain why the circuit fails (no electrical feed) without the breaker popping. I am at a complete loss to explain how a neutral failure would cause continuity between the hot and ground leads in a circuit.

I would be very interested in the theory behind this failure mode. More tomorrow evening......
 
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Old 06-24-04, 09:32 PM
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Take any circuit in your house. Make sure that at least one light is on, or one lamp is plugged in and turned on, somewhere on that circuit. Shut off the breaker. You will measure continuity between hot and ground. It has nothing to do with a neutral failure. As I said before, measuring continuity between hot and ground conveys no information.

Good luck in your hunt for the failed connection. We await your report.
 
  #9  
Old 06-25-04, 02:43 AM
doingitmyself
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Originally Posted by John Nelson
Take any circuit in your house. Make sure that at least one light is on, or one lamp is plugged in and turned on, somewhere on that circuit. Shut off the breaker. You will measure continuity between hot and ground. It has nothing to do with a neutral failure. As I said before, measuring continuity between hot and ground conveys no information.

Good luck in your hunt for the failed connection. We await your report.
Is the "continuity" reading actually a "resistance" reading of, say, the filament of a lamp? Even though the neutral is open, it is still physically and elctrically connected to each other (or should be, anyway) at the main panel, so you should read a resistance (or continuity) between the grounding wire and the hot, if anything is plugged in. The resistance, or continuity of the hot and the ground does not mean that there's a short between hot and ground (ground fault).
 
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Old 06-25-04, 04:43 AM
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The cold resistance of the filament of a 60W 120V lamp is about 25ohms. (Note: resistance changes by about 10x when the filament heats up) For many continuity testers, this is a sufficient connection to indicate continuity.

With the open neutral, you still have the 'hot' connection, so the 'hot to ground' lamp lights on the outlet tester. You also have continuity from hot, through any loads, to the neutral wire, so the 'neutral to ground' lamp lights up on the outlet tester. The same two lamps would light up if the hot terminal was grounded and the ground terminal was hot, so the tester says 'hot-ground reverse'. But if these outlets ever worked in the past, you will not have a hot ground reverse; so open neutral is a better theory to explain which lamps light on the tester.

If you can turn off _every_ load on the circuit, then the 'neutral to ground' lamp should go off on the outlet tester, and the continuity between hot and neutral should vanish.

-Jon
 
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Old 06-25-04, 05:20 AM
thompsdw
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Just checking!!!

The first thing I did prior to any of the tests was to remove any loads (nothing plugged in, all light bulbs removed) from the electrical circuit. Right now, the circuit has nothing on it at all for any current to flow through resistance elements (unless I have missed something mapping the circuit). What I am hearing, is that I should not have continuity to ground in the condition that I have setup. Right?
 
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Old 06-25-04, 05:45 AM
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There should be no continuity between hot and neutral if all the loads are removed. There should never be continuity from hot to ground. There should be _voltage_ between hot and neutral, and there should be _voltage_ between hot and ground, if the circuit is powered and functioning correctly. With an 'open neutral' there should be no continuity between hot and neutral if all the loads are removed, and there will be no voltage between hot and neutral.

If you are absolutely certain that _everything_ is removed (no lights in switches, no outside lights, no bell transformers, etc. and you still have continuity, then it could suggest a 'high resistance' hot to ground fault. This would be a hot to ground fault that doesn't pass sufficient current to trip a breaker.

The thing is, that if you have a high resistance hot to ground fault, the circuit would still be working! Some of the current would go through the fault, and the rest would go through the loads.

The fact that your circuit is _not_ working still points to the open neutral. You should continue mapping the circuit until you find this open neutral, and also until you find the load that you've overlooked. It is possible that you have two problems; the open neutral _and_ a short from the hot wire to the _disconnected_ white wire; my bet is that if you have both, you will find them both at the same time.

Your original theory was that somehow electricity was 'leaking' from hot to neutral, and you were confused by the 'hot/ground reverse' indication from your outlet tester. What you have measured makes it clear that you have a good connection from hot to the circuit, and that the hot is in the right place on the receptacle. Since the receptacles don't work, it is clear that the neutral is open. Finally, since you are measuring continuity between the 'hot' and the 'white' wire, either you still have a load connected, _or_ you have insulation failed between the two.

Now, these two might be in the same place; when a connection fails, you can get lots of heat production without overcurrent. It is possible that when the neutral failed, there was enough heat produced that the insulation failed between the hot wire and the (now disconnected from neutral) white wires.

-Jon
 
  #13  
Old 06-25-04, 06:27 AM
thompsdw
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More good information from you guys ..........

Jon,

Thanks for your post. I agree completely. It is possible that I have not fully mapped the circuit. I will have to chase that lead if I don't find an obvious fault. I have found many skinned wires in the boxes (scarry stuff). I would assume that windings in ceiling fan would also indicate a flow to ground from hot with some resistance. That is the only load left on the circuit that I know of.

I wanted to take a minute to thank everyone for the replies. I frequent many forums and I have never recieve as many rapid responses that were filled with very valuable content. You fellas are great. I helps to have someone think these things through with. My little girl is laying under this maze of wires.

BTW, you will never guess what I found during last nights mapping excercise. My daughters entire room was hot fed (light, fan, 6 receptacles) through a receptacle jumper. The wires were not even pigtailed in the box. Wow - after all the skinned wires and shortcuts like this, I am afraid to look for more.

Am I right on the ceiling fan????
 
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Old 06-25-04, 07:26 AM
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Originally Posted by thompsdw
I would assume that windings in ceiling fan would also indicate a flow to ground from hot with some resistance.
Am I right on the ceiling fan????
No, not if the fan was off. the connection to those windings should be broken.

I'm not sure what you meant about the receptacle jumper. are you talking about a back stab? That would seem pretty normal.
 
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Old 06-25-04, 07:43 AM
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There should never be continuity from hot to ground.
Because the neutrals and grounds are bonded at the main panel, if there is continuity from hot to neutral, there will also be continuity from hot to ground.

If the "receptacle jumper" is the tab on the side of the receptacle, then this wiring technique is common. It's not a short-cut.
 
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Old 06-25-04, 08:18 AM
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It may not be a shortcut but I prefer wire nuts & pig tails to the outlet over the method you describe. I like to use the straded wire tails. It's much easier to change a bad receptacle without disturbing anything else. I am an amateur though so definately defer to the other guys.
 
  #17  
Old 06-25-04, 07:14 PM
thompsdw
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Got the circuit back on line tonight. Corrected many skinned wires in boxes. Replaced numerous receptacles and switches, but I don't think that was the problem. This afternoon I powered the circuit up to the bedroom and measured the voltage at the room. It was ~80 Volts. I started running my power connections backwards again until I found a full 120 Volts. I reconnected the wires and disconnected a item that I had replaced in a replaced attic receptacle. A transformer for the house alarm siren. The thing that I did wrong was I did too many things at once, but with the connections re-done and the transformer unplugged I have full voltage in the room and the circuit is working normally.

The transformer could be the problem. That would explain the intermittent nature of the failure for some time, however, does that explain reduced voltage? Or could the cause of reduced voltage only be a poor connection?

My little girl is sure happy!!
 
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Old 06-09-10, 11:02 AM
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Originally Posted by John Nelson View Post
You do not have a ground fault wiring flaw. You don't even have a hot/ground reverse. You have an open neutral. This is a failed connection of a white wire. 98% of the time it is a failed backstab connection of a white wire. Open up every box on the circuit, whether currently working or not, and reterminate all white wires from the backstab holes to the adjacent screws.

This is not a guess. I've seen this problem hundreds of times. Shut off the breaker and get started.

P.S. Once you get this fixed, I'll explain to you all those symptoms you are currently seeing if you are interested.
I found an OPEN NEUTRAL on an outdoor receptacle. The white wire slipped out the backstab connection the moment I opened the box. That circuit was installed when the house was built over 20 years ago and I have only used it a dozen times over the years. Once I reconnected all the wires in that box to the screws on the receptacle, all the downstream outlets started working properly. The problem was a failed backstab connection. John Nelson, you are the man!
 
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Old 06-09-10, 11:23 AM
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Glad you solved it but you do relize this is a six year old thread and neither Raycraft or John has been here in a long time. Thanks though for the blast from the past and remember map that breaker box as soon as you move in.Beer 4U2
 
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