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Old 08-05-2012, 08:54 AM   #1
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Hot Neutral when Light is screwed in


I'm running a new circuit on a 15amp arc breaker. On the circuit is a switch running 3 can lights. The circuit reads fine when the switch if off, but when turning it on it pops the breaker because the neutral become hot. Here's what I can't figure out.

If the switch is on and the lights are in it reads neutral hot, if I unscrew all the lights the neutral reads zero/dead. If I put a light into any one of the cans, the neutral reads hot again.

I would assume if I messed up wiring the lights, the neutral would always read hot regardless of the lights being screwed in. However, I can't figure out why have a bulb in one of the cans would create a hot neutral. The lights are all daisy chained off each other with pigtails, so the black should run live across all 3 lights, same with the whites and grounds. Single pole switch. (i've also taken the switch out of the equation and created a direct line to the lights as well to test that as the issue).

Thoughts?

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Old 08-05-2012, 09:24 AM   #2
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Hot Neutral when Light is screwed in


You have an open neutral and the lamps are backfeeding the neutral with voltage through the filament.
Find the open neutral and you'll find your problem.

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Old 08-05-2012, 09:38 AM   #3
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Hot Neutral when Light is screwed in


What are the typical causes of an open neutral? A nicked wire, neutral that became disconnected, etc?

Is there anyway to narrow down where the live neutral is coming from, given I have three lights on the circuit?

Last edited by davygravy; 08-05-2012 at 09:43 AM.
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Old 08-05-2012, 10:00 AM   #4
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Hot Neutral when Light is screwed in


How did you wire up the AFCI breaker?
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Old 08-05-2012, 10:16 AM   #5
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Hot Neutral when Light is screwed in


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Originally Posted by davygravy View Post
What are the typical causes of an open neutral? A nicked wire, neutral that became disconnected, etc?

Is there anyway to narrow down where the live neutral is coming from, given I have three lights on the circuit?
You're not looking for a live neutral, you're looking for an open neutral. It could be anywhere on the circuit, you have to physically check.

Kbuz brings up a good point. Did you wire the AFCI breaker properly?
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Old 08-05-2012, 11:15 AM   #6
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Hot Neutral when Light is screwed in


About the switch that trips the breaker when flipped on ... did you install that yourself? You made a mistake in wiring it. You never connect a neutral to a swith terminal.

Occasionally a white wire is used to bring power down to a switch when the power enteres the light box first. It is connected to the bundle of blacks up at the light fixture, not the bundle of whites. (The wire carryuing power back to the light must never be white.) The most modern code (National Electric Code for 2011) requires that a real neutral be brought to each switch box and typically you run a 3 wire cable using red and black for the switch.
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Last edited by AllanJ; 08-05-2012 at 12:07 PM.
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Old 08-05-2012, 11:18 AM   #7
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Hot Neutral when Light is screwed in


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About the switch that trips the breaker when flipped on ... did you install that yourself? You made a mistake in wiring it. You never connect a neutral to a swith terminal.
I think he is tripping the AFCI, not the actual breaker...but I could be wrong.
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Old 08-05-2012, 11:26 AM   #8
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Hot Neutral when Light is screwed in


K_Buz - My father in-law an ex-electrician from 15 yrs ago installed the breaker. It sounds like that could easily be the problem, I don't know how, but I'll have him look at it again. He also wired a 20amp arc breaker and we're not having issues with that for the outlets in this same 4 season porch.

Allan - So I originally wired up the switch and upon flipping the breaker it would pop. So I went up, took the switch out and wired the circuit directly to the lights, breaker on = lights on. Still popped. Then I disconnected the light neutral from the circuit neutral, flipped the breaker and it didn't pop. Tested the neutral and found it was hot. Take all the lights out, reads zero, put any of the 3 lights in, it's live. I only ran black (hot), white (neutral) and a ground for all parts of this single pole circuit. Apologize if I missed the point of your comment, let me know.

Can someone explain to me what "Open" neutral means? How does that occur?
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Old 08-05-2012, 11:35 AM   #9
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Hot Neutral when Light is screwed in


An open neutral is when the white wire isn't continuous back to the panel. There is a break in it somewhere. It could be a loose connection, a mis-spliced box, a broken wire, or the AFCI breaker is wired wrong.

An open neutral will not trip the breaker. It will trip the AFCI portion of the breaker tho. This is one of the downfalls of the AFCI's. You don't know what is actually happening, is it a direct short, or is it something else causing the AFCI to trip.

In your case, it sounds like the AFCI is tripping.

You need to open the panel, make sure the white from the circuit is going to the breaker, and the white from the breaker is going to the neutral bar.

If that is true, then you need to retrace the circuit and check all neutral (I would double check all the splices you made) splices.
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Old 08-05-2012, 11:37 AM   #10
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Hot Neutral when Light is screwed in


An open neutral is a bad or loose connection.
Check all connections at each light, and the breaker.

Its possible the insulation has been compromized in some of the wiring. Check it for damages as well.
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Old 08-05-2012, 11:52 AM   #11
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Hot Neutral when Light is screwed in


Thanks Mister Z. I just hard wired an extra light I had to the switch box and the everything worked fine, leading me to believe the breaker is wired correctly and the issue is somewhere out in the 3 can lights.

Time to take off the sofets and facia and get into it.

Thanks.

If I didn't use an arc breaker, would this issue be happening?
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Old 08-05-2012, 12:03 PM   #12
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Hot Neutral when Light is screwed in


Are outside lights the only thing on this breaker? If so, you do not need an AFCI...but you still need to figure out where the neutral is open.
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Old 08-05-2012, 08:23 PM   #13
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Hot Neutral when Light is screwed in


I found a frayed neutral line in the brand new Juno can light. Have to say, in addition to the $23 trim, another reason I dislike Juno vs. Halo.

I also revisited every connect and the neutral is now reading zero. However a new and odd scenario has presented itself. Let me know what you experts think.

When I plug directly into the can light switch everything works. When I plug directly into the flood light switch everything works. However, upon pigtailing the two switches off the same circuit it trips. If I leave both switches off there's not trip, if I switch the flood light on, no trip. However, if I switch the cans on with or without the flood light on it trips. However, it runs fine with no hot neutral or flipping the breaker if it's a dedicated circuit.

Thoughts? Hoping to pick up a switch or two tomorrow to test out a failure there, but again, they work when tested individually. (single pole dimmer, single pole on/off switch).
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Old 08-05-2012, 09:03 PM   #14
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Hot Neutral when Light is screwed in


Dead short on switch?
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Old 08-05-2012, 09:16 PM   #15
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Hot Neutral when Light is screwed in


Ex- electrician? Like Ex-Marine. No such thing. But they always said Oswald was an x marine.

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