neutral question

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Zef

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Location
new york
when a circuit completes itself it comes back on the neutral at 120v but why when you land the neutral on the neutral buss bar nothing happens?
 

roger

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Fl
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Retired Electrician
I'm not sure I understand what you are asking but here goes.


If there is no load present there is no voltage dropped so there is no current flow.

If a load is present there will be an arc.

Roger
 

infinity

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Location
New Jersey
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Journeyman Electrician
Do you mean nothing happens in relation to a grounded surface like the panel enclosure?
 

brian john

Senior Member
Location
Leesburg, VA
If there is a load on the circuit and you lift the neutral there will be as noted a spark, in addition there will be voltage between the lifted neutral conductor and ground and the grounded/neutral termination bar.

If this is a neutral for a MWBC (multi-wire branch circuit) and you lift the neutral with a unbalanced loads you can and most likely will fry one or both of the loads on the MWBC.
 

jwjrw

Senior Member
I installed a sub panel today. I removed (2) two wire with ground 14-2 circuits. I went to move them out of my way and my elbow touched the new panel and I grabbed the neutral and ground. It lit me up pretty good (I thought when it first happened) I jerked my other elbow when it happened and shut the main off (reaction not on purpose). One neutral had .5 amp on it when I checked it at that time. But I checked it again before I left and it was .9 amp. I see neutrals in older homes tied together a lot here.
 

jwjrw

Senior Member
don't you mean it lit you up BAD? It is never good.

Ever hit your funny bone when working on a de-energized circuit and think you were hit and freak for a 1/4 second?



Had it really had a load on it I agree it would of been bad. I at first thought I must have hit something in the old panel which was still hot. Then I brushed each neutral on the neutral bar and found the one. It just caught me off guard. :D
 

Dennis Alwon

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Retired Electrical Contractor
I am going to guess that the OP is saying that 120V flows from the hot conductor thru a load and thus that neutral has 120V on it, however when you install that wire with 120V potential to the neutral bar there is no short circuit.

Thus if you went right from the breaker to the neutral you would have a short but go thru the load and there is no short.
 

jwjrw

Senior Member
I am going to guess that the OP is saying that 120V flows from the hot conductor thru a load and thus that neutral has 120V on it, however when you install that wire with 120V potential to the neutral bar there is no short circuit.

Thus if you went right from the breaker to the neutral you would have a short but go thru the load and there is no short.[/QUOTE]


And that is a hard concept for a lot of guys to understand. I think every helper I have ever had asks that question about 240 volt heating elements
 

Dennis Alwon

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Chapel Hill, NC
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Retired Electrical Contractor
I could try and answer this but I am not sure my answer will be what will help the OP understand. My answer would be it has to do with resistance on the circuit when there is a load.
 

Smart $

Esteemed Member
Location
Ohio
Landing the neutral of an energized circuit (recommend not doing this regardless of knowledge and/or experience) is the same as flipping a switch in one that is already landed and energized.
 

S'mise

Senior Member
Location
Michigan
when a circuit completes itself it comes back on the neutral at 120v but why when you land the neutral on the neutral buss bar nothing happens?

What did you expect to happen?

It does not "short out" because the grounded neutral buss is only half of the circuit. Similar to how the grounded negative side of a car works. The returning neg 12v from the lights may apear to "do nothing" but its completing the circuit and alowing current flow. By grounding one side of the source does not short the battery.
 

Zef

Member
Location
new york
Not really, when i say nothing happens why doesnt it short out when you land the neutral on the neutral bar? because there is 120v coming back on it.
 

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
101130-1729 EST

Zef:

You need a book on electrical circuit theory. Start with simple DC circuits.

I will try to explain several points.
when a circuit completes itself it comes back on the neutral at 120v but why when you land the neutral on the neutral buss bar nothing happens?
What exactly were you asking here? I am not sure.

Consider a very simple circuit.
http://en.wikipedia.org/wiki/Series_and_parallel_circuits
At the beginning of the article is a simple series circuit of a battery and three resistors in series. Consider the top resistor to be your hot wire , the right hand resistor the load , and the bottom or your neutral wire.

Use the bottom end of the battery as ground, your neutral bus bar, and a reference point for voltage measurements.

Assume the battery is 10 V. Assume the top and bottom resistors are 0.1 ohms, and the right hand resistor is 9.8 ohms.

Open the connection at the top (+) end of the battery. Measure the voltage across the battery. This will be 10 V. Measure the voltage from the negative end of the battery to any other point in the circuit and the voltage will be 0 V.

Reconnect the top resistor to the + battery terminal.

What is the current flow in the circuit? I = V/R = 10 / (0.1 + 9.8 + 0.1) = 10 / 10 = 1 A.

Relative to the battery negative end what is the voltage at each point in the series circuit? 10.0, 9.9, 0.1, 0.0 .

Next open the lower right corner. What is the voltage at the right end of the bottom resistor? 0.0 V. What is the voltage at the bottom end of the right resistor? 10.0 V.

Reconnect the lower right corner, open the connection of the bottom resistor to the negative end of the battery. What is the voltage of the left end of the bottom resistor? 10.0 V. What is the voltage of the bottom end of the right resistor? 10.0 V. If this were a 120 V circuit and you touched one hand on the negative end of the battery and the other hand on the neutral wire you would get a severe shock, and maybe kill yourself.

Now suppose the right hand resistor is infinite, an open circuit for the load. What is the voltage at the right hand end of the bottom resistor (your neutral)? 0.0 V. Same at the left hand end.

Can you start to see what happens in the circuit of your original post?

.
 
Location
NE (9.06 miles @5.9 Degrees from Winged Horses)
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EC - retired
don't you mean it lit you up BAD? It is never good.

Ever hit your funny bone when working on a de-energized circuit and think you were hit and freak for a 1/4 second?

Touched a disconnect in a basement about the time I bumped my elbow on a short concrete wall under it. Funny bone was first thought. Second thought was what saved my rear that time. Energized.
 
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