This is a weird failure...

Thread Starter

Externet

Joined Nov 29, 2005
2,201
Hello.
Plugged my circular saw in the outlet; cut a piece of wood... fine. Did it again for a second piece of wood... fine. The saw did not work for a third cut. No power. No bangs, no sparks.

Inspecting, no circuit breakers tripped. The outlet for the saw presented 'live' on both the black and the white (neutral) slots. (live of same phase) No neutral presence. So no 120VAC at the outlet. Digging deeper, have not found yet what happened. Two other rooms that were not in use lost power in the house.
There is nothing abused, wet, old, corroded, no history of faults, has been a healthy electrical system until today.

Found a neutral (white) wire bundle in a wall light switch box being 'live', probably a branch of the failed outlet. Lights did not turn on as both live and neutral wires had the same 'live' phase. Will continue to diagnose painfully guess-tracking the wiring inside walls, scratching my head. Never seen this. :oops:
 

Jon Chandler

Joined Jun 12, 2008
1,029
It's hard to conceive of any mechanism where the neutral becomes disconnected and the hot takes its place.

What may have happened is that the neutral is broken somewhere, and the 120v you're measuring is just leakage through some connected load or capacitive coupling from the hot wire.
 

jiggermole

Joined Jul 29, 2016
161
Another posibility that ive seen is an metal oxide varistor on a power strip failed. In the event of an overvoltage this is supposed to conduct and save anthing downstream. In this case it failed shorted, almost, and was throwing off all attempts to troubleshoot until that power strip was unplugged.
 

Thread Starter

Externet

Joined Nov 29, 2005
2,201
Has to be a neutral fault. A neutral splice or joint opened by the high saw current. The hard part is where in the whole house o_O

The 'live' phase has to be passing onto the neutral trough one of several night lights plugged in the same circuit, or something permanently on... Am using plain voltmeter and contact-less sniffer.
Waiting for day time and adrenaline to troubleshoot and diagnose 'fun' Thanks.
 
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xox

Joined Sep 8, 2017
838
So...just to be clear here, this "floating neutral fault" presents the live wire voltage because it is connected through the load, correct? Which is to say, if no load were connected then the neutral wire would instead be "dead". Is that right?
 

strantor

Joined Oct 3, 2010
6,782
I hate twist nuts with a passion. Only WAGO Lever nuts are authorized in the shop.
Good thing there aren't many American electricians around here or this statement could start WWIII.

I prefer Wago Lever Nuts too. Electricians will point out (emphatically) that twist-type wirenuts provide a better connection, physically wire-on-wire, not passing current through a tiny strip of metal in the connector. True, but they only do that when used properly, and far too many people don't use them properly. Can't tell you how many times I've troubleshot an issue down a wire pulled out of a wirenut.
 

Thread Starter

Externet

Joined Nov 29, 2005
2,201
So...just to be clear here, this "floating neutral fault" presents the live wire voltage because it is connected through the load, correct? Which is to say, if no load were connected then the neutral wire would instead be "dead". Is that right?
Better a graphic: Seems simple but when the failure surfaced, was a mind twister, specially with the unsuspected night lamp in another room/level of the house. It could had been a clock, a charger... anything meant to be permanently energized.:oops:
1680095864374.png
Red is phase/hot/live. There was no wire nut, only twisted wires under insulating tape as the black ones next. I put the red one.
 
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strantor

Joined Oct 3, 2010
6,782
the unsuspected night lamp in another room/level of the house.
o_O

There was no wire nut, only twisted wires under insulating tape.
:mad:

Sounds like an overconfident handyman (or someone who fancies themselves as such) has been unleashed on your house in the past. This isn't good news I'm afraid. That was a fire hazard and if they did it there, they probably did it elsewhere too.
 

Thread Starter

Externet

Joined Nov 29, 2005
2,201
The first thing I did when bought the house was to rewire all outlets to wrap the wires tight on the screws instead of the idiot lazy way of leaving inserted in the locking holes. But will not destroy more walls to look at very hidden splice boxes... :rolleyes:

1680098251444.png
 

jiggermole

Joined Jul 29, 2016
161
In response to the wago comment. American electrician and I prefer wagos as well. Not the knock offs the real wagos. The knock offs connect the wires with a blade that cuts into the copper. Real wagos compress the wire to a bus bar. So in reality the connection on a wago is no worse or better than a wire nut.
So why not use the wrist friendly wago and save myself the carpel tunnel.
And to the op, knob and tube wiring is still a thing in many many houses here. And having the grounded conductor not properly bonded is pretty common too. Pretty annoying when you're asked to install a gfci and have to un-bork their panel before it works correctly.
 

nsaspook

Joined Aug 27, 2009
13,086
In response to the wago comment. American electrician and I prefer wagos as well. Not the knock offs the real wagos. The knock offs connect the wires with a blade that cuts into the copper. Real wagos compress the wire to a bus bar. So in reality the connection on a wago is no worse or better than a wire nut.
So why not use the wrist friendly wago and save myself the carpel tunnel.
And to the op, knob and tube wiring is still a thing in many many houses here. And having the grounded conductor not properly bonded is pretty common too. Pretty annoying when you're asked to install a gfci and have to un-bork their panel before it works correctly.
and most of the popular circuit types have a test point on each connector to monitor the voltage/continuity at that point. Easy access, no need to disconnect unless needed for something else.

1680155515726.png1680155539094.png
 
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