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Old 09-24-2017, 08:15 PM   #1
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Default Symptoms of an open neutral

can someone please shed some light on this. I've seen two separate cases in which the answer was an open neutral. both had 120v H to G and 0 H to N. the difference was N to ground for one was 0 and the other was 120. i cant figure out how these two exact opposites can point to the same conclusion.
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Old 09-24-2017, 08:33 PM   #2
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Your neutral will have 120 volts to ground if the bonding is open between the ground and neutrals and there is a closed switch feeding it.
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Old 09-24-2017, 10:19 PM   #3
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Draw out each circuit with it's fault. Then you will see why two different symptoms are the same problem. Were all measurements taken at the same points under the same conditions?
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Old 09-24-2017, 10:28 PM   #4
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can someone please shed some light on this. I've seen two separate cases in which the answer was an open neutral. both had 120v H to G and 0 H to N.

[ If the neutral is pulled high it is also at 120V to G. This is to be expected any time a connected load allows the Hot to bleed voltage through to the Neutral. This can be a plugged in load like a wall wart or an incandescent lamp.

Such values are the classic sign that you're looking at an open neutral. ]

the difference was N to ground for one was 0 and the other was 120.

[ In this instance, no path from the Hot to the Neutral exists ( ie through a resistive or inductive load ) ... but the Neutral is still broken. ]

i cant figure out how these two exact opposites can point to the same conclusion.
Does that clear it up ?
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Old 09-25-2017, 10:21 PM   #5
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Sorry guys I'm still not getting it
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Old 09-25-2017, 10:25 PM   #6
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If you power a light and then remove the neutral wire from the neutral bus, you will have 120 volts from that neutral to ground.
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Old 09-25-2017, 10:35 PM   #7
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Symptoms of an open neutral
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Sorry guys I'm still not getting it
Get a pencil and paper and draw a couple of 120V circuits with/without loads and it may become clear.

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Old 09-25-2017, 11:30 PM   #8
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Get a pencil and paper and draw a couple of 120V circuits with/without loads and it may become clear.
It may become clearer to the experienced, but for someone entering the trade- the experienced have long forgotten what it is like to be the FNG.

Just a tip- and just the tip, break it down like its a homeowner.... You'll soon see where the experienced have lost touch.
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Old 09-26-2017, 04:29 PM   #9
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I couldn't explain it to a homeowner. I can only explain it to guys I teach by using a pencil and paper. Hell, I could only understand it myself by using a pencil and paper.

My brain like to follow lines.
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Old 09-26-2017, 05:34 PM   #10
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Whether you have 120 or 0 between N and G depends on where the neutral is broken and whether a circuit that involves that neutral is energized with a load.

Like others said, try drawing it out.
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