Loose Neutral Wire

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  #1  
Old 06-23-05, 11:37 AM
jay12345
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Loose Neutral Wire

Hi, I recently ran into a situation I was hoping someone could shed light on...

The situation:

- While wiring power from the house panel to a garage a neutral wire was broken on a 2Pole 15 amp breaker.

- As far as I can tell this breaker feeds two outlets and the only thing plugged in to either one was a telephone attached with a 9V power adapter.

- The phone continued to operate for a couple of hours that night but the next morning was no longer functional and had a "burning smell" coming from it.

The question:

Someone told me that this was just a coincidence for two reasons: The phone could not have been exposed to excess voltage due to the prescence of the 9V power adapter (which was still working properly) and the fact that nothing else was plugged in on the same circuit breaker. The presence of another resistance on the circuit was "necessary" in order to create an inbalance of voltage between the two units.

What I am wondering is if this is correct and it truly is VERY coincidental, or is it possible that the loose/broken neutral connection did cause the problem?

If you could provide any insight into this (or somewhere I could look to for answers) at all it would be appreciated.
 
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Old 06-23-05, 11:51 AM
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Was this actually the neutral wire or did someone not correctly re-identify it as a hot conductor?

Normally neutral wires do not attach to a breaker unless it is a GFI or AFCI breaker.
 
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Old 06-23-05, 12:07 PM
jay12345
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It was the neutral wire that was broken, after looking over my original post it sounds like the neutral was on the breaker itself, but it was actually on a neutral bus bar in the panel.
 
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Old 06-23-05, 12:16 PM
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2 pole breaker would indicate to me a multiwire circuit. Yes the broken neutral probably caused the voltage to go high and burn out the phone. Do you know what is on the other side of the two pole breaker? If the neutral hasn't been fixed the breaker should turned off NOW.
 
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Old 06-23-05, 12:18 PM
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As you may or may not know, this is a "multiwire" circuit. And multiwire circuits are very intolerant of open neutral connections (which is the reason that the code has special requirements to reduce the likelihood of an open neutral). When an open neutral occurs on a multiwire circuit, voltages fluctuate above and below the normal 120 volts.

The 9-volt power adaptor does not completely insulate the appliance from voltage fluctuations in the supply. Furthermore, the most likely failure is of the power adaptor itself. Is the smell coming from the power adaptor, or the phone? It may have damaged both.

Special care needs to be taken to avoid open neutrals on multiwire circuits. For this reason and many others, I generally discourage the use of multiwire circuits in all but very special circumstances.

I don't think that this is a coincidence at all. It is, however, true that this could not happen if there were absolutely no other loads on this double-pole breaker at all. But I suspect that there was at least one other load you have overlooked.
 
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Old 06-23-05, 12:28 PM
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Just a point of curiosity:

I know that multiwire circuits must be on opposite legs and use neutral wire pigtails with wirenuts instead of "pass-through" receptacles. They also must use a tied-handle breaker if both legs connect to the same "yoke". Are there other special requirements of multi-wire circuits? I have a couple in my house, and I'm curious if there is anything else to look for.
 
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Old 06-23-05, 12:45 PM
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ibpooks, I think you covered it pretty well.
 
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Old 06-23-05, 12:48 PM
jay12345
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Since this problem occurred the neutral wire has been fixed so it does not currently pose any problems.

The power adapter is undamaged and still works properly, while the phone (this is where the smell was coming from) is dead.

I tested every outlet in the house with the breaker switched off and only two of the kitchen outlets appear to be on the circuit (and only the phone was plugged into either of them). Is it possible that anything else would be connected to this circuit like a light (I didn't think this was permitted with kitchen plug-ins)?

Thanks for everyones reply so far.
 
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Old 06-23-05, 12:55 PM
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Certainly it's possible that a light is on this circuit. Shut off that double-pole breaker and see what loses power. You should do this anyway for all your circuits, since an accurate list of what loads are on what circuits is essential for any homeowner. And do it before you have another problem, since when the power goes out, it's no longer possible to make this list, and you may need the list to resolve the problem. Everybody, not just you, should do this this weekend.
 
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Old 06-23-05, 12:58 PM
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Thanks John for the confirmation.

The dishwasher and disposal aren't supposed to be on the same circuit as the countertop receptacles, but it is a possibility one or both of them is also on this MWC. Did you check those?
 
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Old 06-23-05, 01:04 PM
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Jay,

It is true that kitchen counter receptacles cannot serve lights. However, this is code now. It was not always code. In addition, when homeowners add their own circuits they don't always follow code even if they know what code is and understand why it is.

Today, a kitchen counter circuit cannot serve lights. It must also be 20 amp. There are other restrictions too.
 
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