just how dangerous is the neutral wire?

In the 3-wire 120/240 volt Edison style single phase wiring system as found in North American, a neutral can be shared between opposite phases, carrying only the current for the
imbalance between the phases. In times long ago, there was no separate grounding wire; the neutral served as the ground. But the grounding wire was added, initially required only on some circuits (the laundry room was first).
Clearly there is some level of hazard in the neutral wire. But just how much? Clearly it is a big hazard if it becomes disconnected from its source, and the imbalance between the phases is now a voltage on that wire, energizing everything that is connected to it (as was the common case decades ago).
But what I'd really like to know is how safe is it in normal connections where it is properly connected, but may be run some distance from where it is bonded to ground, possibly via a subpanel where other circuits could contribute some voltage to it when running out of balance.
Q: Would you feel safe grabbing a neutral (presume you are absolutely positive it is not a hot wire) while standing in bare feet on a wet concrete slab?
Q: Would you feel safe sitting in a tub with the neutral wire either within reach, or dangling into the tub itself?
Here's where I'm going with this. Certain situations require ground fault circuit interruptor protection to prevent shock on a ground fault path. These are generally "wet" situations such as the electrical systems of a hot tub of jacuzzi. The idea is if something goes wrong and a path to the water is set up, a small leakage current will interrupt the circuit. But the issue is that in the case of 240 volt loads, GFCI is done via a 2-pole circuit breaker. The neutral runs through the breaker to be part of the leakage measurement, but it is not disconnected when the breaker is tripped off. There are such things as a "switched neutral" breaker for places where a neutral voltage is recognized as a danger, but these are not GFCI breakers.
So basically, this GFCI protection does not disconnect the neutral wire. I'm told that most GFCI receptacles for 120 volts do disconnect the neutral.
Where can one find a GFCI protection device that disconnects both hot phase wires and the neutral at the same time?
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I believe that much of the hazards around the neutral have been eliminated by the separate grounding conductor. In years past, many appliances and such had the *frame* tied to the neutral. This became quite dangerous whenever the neutral developed a problem (such as an open). Old tube radios often had one wire from the outlet tied to the frame/chassis. Lose a knob on the front and touch the metal shaft and you could be in for a surprise.
Newer requirements have the frame completely isolated from the electrical circuit. This goes a long way in minimizing any risk associated with the neutral opening since you still can't easily become part of the circuit.

Well, some may, but I don't feel completely safe anytime I work on wiring near water. Just sort of an ingrained fear I guess. But it helps keep me alive :-)

A neutral that goes back to the panel and is not part of a multi-wire circuit cannot present a hazard when both 'hot' wires are deenergized. It can only be a risk when a hot lead is powered (and the return to the panel is poor/broken). Once the two hot leads are opened, I cannot see how a neutral can present any hazard. (unless it is improperly shared with another circuit). I believe this is why 2-pole GFCI's are made this way. There is no reason for more protection (paranoia??)
daestrom
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wrote:
| |> In the 3-wire 120/240 volt Edison style single phase wiring |> system as found in North American, a neutral can be shared |> between opposite phases, carrying only the current for the |> imbalance between the phases. In times long ago, there was |> no separate grounding wire; the neutral served as the ground. |> But the grounding wire was added, initially required only on |> some circuits (the laundry room was first). |> |> Clearly there is some level of hazard in the neutral wire. |> But just how much? Clearly it is a big hazard if it becomes |> disconnected from its source, and the imbalance between the |> phases is now a voltage on that wire, energizing everything |> that is connected to it (as was the common case decades ago). |> |> But what I'd really like to know is how safe is it in normal |> connections where it is properly connected, but may be run |> some distance from where it is bonded to ground, possibly via |> a subpanel where other circuits could contribute some voltage |> to it when running out of balance. | | I believe that much of the hazards around the neutral have been eliminated | by the separate grounding conductor. In years past, many appliances and | such had the *frame* tied to the neutral. This became quite dangerous | whenever the neutral developed a problem (such as an open). Old tube radios | often had one wire from the outlet tied to the frame/chassis. Lose a knob | on the front and touch the metal shaft and you could be in for a surprise.
So explain to me how the neutral wire itself is no longer a hazard due to the fact that the grounding wire now exists? Are you willing to touch the neutral wire to your tongue while standing barefoot on wet concrete just becuase a grounding wire exists?
I think you completely misunderstand my statement.
| Newer requirements have the frame completely isolated from the electrical | circuit. This goes a long way in minimizing any risk associated with the | neutral opening since you still can't easily become part of the circuit.
I'm not asking if equipment frames are safe. I know they are safer since they connect to the grounding wire instead of the neutral wire. My question is how safe is that NEUTRAL WIRE. The fact that we do connect equipment frames to the grounding wire tells be the neutral wire is a hazard, and as such it SHOULD BE DISCONNECTED when a circuit is disconnected, especially in wet situations.
|> Q: Would you feel safe grabbing a neutral (presume you are |> absolutely positive it is not a hot wire) while standing in |> bare feet on a wet concrete slab? |> |> Q: Would you feel safe sitting in a tub with the neutral wire |> either within reach, or dangling into the tub itself? |> | | Well, some may, but I don't feel completely safe anytime I work on wiring | near water. Just sort of an ingrained fear I guess. But it helps keep me | alive :-)
Same for me.
|> Here's where I'm going with this. Certain situations require |> ground fault circuit interruptor protection to prevent shock |> on a ground fault path. These are generally "wet" situations |> such as the electrical systems of a hot tub of jacuzzi. The |> idea is if something goes wrong and a path to the water is |> set up, a small leakage current will interrupt the circuit. |> But the issue is that in the case of 240 volt loads, GFCI is |> done via a 2-pole circuit breaker. The neutral runs through |> the breaker to be part of the leakage measurement, but it is |> not disconnected when the breaker is tripped off. There are |> such things as a "switched neutral" breaker for places where |> a neutral voltage is recognized as a danger, but these are |> not GFCI breakers. | | A neutral that goes back to the panel and is not part of a multi-wire | circuit cannot present a hazard when both 'hot' wires are deenergized. It | can only be a risk when a hot lead is powered (and the return to the panel | is poor/broken). Once the two hot leads are opened, I cannot see how a | neutral can present any hazard. (unless it is improperly shared with | another circuit). I believe this is why 2-pole GFCI's are made this way. | There is no reason for more protection (paranoia??)
You have 120/240 volt service into your house. From the house you run a 100 amp subpanel to the detached garage. On the back of the detached garage you have deck with an outdoor hot tub. The equipment powering said tub is connected through a 50 amp 2-pole GFCI breaker, connected to the garage subpanel, connected to the house service panel. Someone is using some heavy duty 120 volt equipment in the shop in the garage. How many volts will you read between the neutral and the ground? I think the answer will be whatever the voltage drop is between the garage subpanel and the house service panel for the current being drawn for whatever wire gauge is installed. Whatever that is, you'll still have that voltage at the hot tub even if the GFCI trips due to some malfunction. Tell me how hazardous you think that is. And if you say it's nothing to worry about, then why not just connect everything to the neutral like used to be done.
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question
Why? If all the "hots" are disconnected, there is no current flow in the neutal and it will be a "cold" as any ground. And since any REAL switch will open one conductor slightly before another, you are more likely to get a 120 volt "glitch" on the neutral if you switch it than if you just leave it connected.
The various remarks about putting one's tongue on the neutral are just plain silly. Practical people don't want to touch ANY thing of metal when working around electricity except for the special case of where they want to ensure they haven't picked up a static charge that might "zap" some silicon.
If you MUST tough metal you touch "ground" first, then neutral and you just DON'T touch hot.

wiring
me
It
panel
way.
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|> I'm not asking if equipment frames are safe. I know they are safer since |> they connect to the grounding wire instead of the neutral wire. My | question |> is how safe is that NEUTRAL WIRE. The fact that we do connect equipment |> frames to the grounding wire tells be the neutral wire is a hazard, and as |> such it SHOULD BE DISCONNECTED when a circuit is disconnected, especially |> in wet situations. | | Why? If all the "hots" are disconnected, there is no current flow in the | neutal and it will be a "cold" as any ground. And since any REAL switch | will open one conductor slightly before another, you are more likely to get | a 120 volt "glitch" on the neutral if you switch it than if you just leave | it connected.
If it is that safe, then we didn't need to add all these grounding wires to receptacles, as the neutral would be sufficient. But someone obviously thought different as early as 1947 or before, since that's when it started showing up in the NEC.
| The various remarks about putting one's tongue on the neutral are just plain | silly. Practical people don't want to touch ANY thing of metal when | working around electricity except for the special case of where they want to | ensure they haven't picked up a static charge that might "zap" some silicon. | | If you MUST tough metal you touch "ground" first, then neutral and you just | DON'T touch hot.
What is the reason for GFCI protecting a hot tub if people are not touching the wires? Well, I think the reason is because something can go wrong. Maybe water can leak into the eletronics and create a path from a wire to the people. As you step in or out of the tub, you could then complete a circuit between that wire and real ground. If there was no risk of voltage on the neutral, we wouldn't have to have separate grounding wires. IMHO, it's only the groundING wire that needs to stay connected. The neutral is groundED somewhere, but that can be far away, and there is no option to allow additional grounding nearby (as that creates the dual return path problem).
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Don't look BUT most "stuff" today is double insulated. The "ground" pin just isn't used by a lot of things. The computer plugs still have "ground" but anything that uses a "wall wart" or and AC/DC converter isn't "grounded." In the kitchen, most food processors and toasters and mixers don't use the third pin.
What the "third pin" does right is that USUALLY, it is connected first and disconnected last. In a two wire plug or a three wire 120/0/120 plug the neutral CAN be disconnected first.

So? Back in 1947 (or whenever) women would use a clothes washing machine that was connected to an overhead combination suspended lamp holder and outlet. They often would plug in the washer with soap/water covered hands. The third pin was an improvement that allowed "backward compatibility." The third pin also provides a greater margin for wiring errors.
"Starting from scratch" we would be as well served by oversized neutrals and plugs than ensured the neutral/ground was made BEFORE the hots.
If you want to worry about the neutral getting lethal voltages then you might was well worry about the "ground" getting lethal voltages. In the real world, it's much easier for the ground connection to be broken and then crossed with HOT than it is for the neutral.

plain
want to

silicon.
just
Duh!
Well, sport, IF somehow the neutral is broken then GROUNDED objects are more dangerous than "floating" objects. Were "ground" and "neutral" permitted to be crossed wheneven convenient it would almost be impossible for all paths to the panel neutral to be broken.

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| Don't look BUT most "stuff" today is double insulated. The "ground" pin | just isn't used by a lot of things. The computer plugs still have "ground" | but anything that uses a "wall wart" or and AC/DC converter isn't | "grounded." In the kitchen, most food processors and toasters and mixers | don't use the third pin.
Nor would they need to with GFCI around. But a hazard exists if the neutral wire is not interrupted when there is some fault path to ground. As I understand it, 120 volt GFCI receptacles do disconnect the neutral when they trip. I will eventually test this.
| So? Back in 1947 (or whenever) women would use a clothes washing machine | that was connected to an overhead combination suspended lamp holder and | outlet. They often would plug in the washer with soap/water covered | hands. The third pin was an improvement that allowed "backward | compatibility." The third pin also provides a greater margin for wiring | errors. | | "Starting from scratch" we would be as well served by oversized neutrals and | plugs than ensured the neutral/ground was made BEFORE the hots.
If "starting from scratch", my design would not use a 3-wire Edison system. I'd go with the European system or some approximation of it.
| If you want to worry about the neutral getting lethal voltages then you | might was well worry about the "ground" getting lethal voltages. In the | real world, it's much easier for the ground connection to be broken and then | crossed with HOT than it is for the neutral.
The neutral doesn't have to be broken and crossed over for it to get voltages that can be lethal to some people.
|> What is the reason for GFCI protecting a hot tub if people are not |> touching the wires? Well, I think the reason is because something can |> go wrong. | | Duh!
But if not all the current carrying wires are disconnected, it's only a job 2/3's done.
| Well, sport, IF somehow the neutral is broken then GROUNDED objects are more | dangerous than "floating" objects. Were "ground" and "neutral" permitted to | be crossed wheneven convenient it would almost be impossible for all paths | to the panel neutral to be broken.
The neutral doesn't have to be broken and crossed over for it to get voltages that can be lethal to some people.
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Nope!
The neutral wire just isn't dangerous.

That they do (at least the one I took apart did.) But in that case they are protecting folks from improper installation whereby neutral and hot are reversed. Disconnecting the "neutral" when it really is "hot" is a GOOD IDEA.
You can test it yourself with a cheap (or expensive) VOM. "Test" the GFCI and then measure the voltages to GROUND. THEN (if zero voltage is found) measure the resistance between neutral and ground.

machine
wiring
and
system.
The UK system (0-240) is inferior to the US 120-0-120 system from a safety view. It "looks good" because the UK uses mostly 240 volt appliances whereas in the US just about no "portable" device uses 240. The UK outlets and plugs are in a different league than the US version.

the
then
Gad! Then those "some people" must live in terror of 9 volt "transistor" batteries, door bell circuits, and telephones.

The job is DONE when the hots are disconnected.

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volt "transistor"

you just resign yourself to sudden death at any turn and then its not a problem.
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wrote:

The "ground" pin

still have "ground"

converter isn't

toasters and mixers

exists if the

path to ground.

the neutral

Thats because the neutral IS grounded a the transformer..so its a ground also to that extent...even though it can carry significant actual power, that power is on a wire dead nuts bolted to the utility company GROUND... so what flows through YOU will be a direct and hard core mathematical function of the your bodys resistance and the resistance in the contact between your body and ground (say zero if you standing salt water on a cement floor_...and the resistance in the neutral cable going to the utility company's grounding grid...which is typically a thousandths of your body resistance.
I dont have the time to run those calcs for you but someone else will. But yes you could still be hurt if there is a significant unbalanced ground and say the utility company neutral is poorly connected at any point.
Making the juice inherently safe will never happen. same with red heads, fast cars and liquor.
Phil Scott

washing machine

lamp holder and

soap/water covered

"backward
margin for wiring

oversized neutrals and

hots.
Edison system.

voltages then you

voltages. In the

be broken and then

it to get

people are not

something can

it's only

GROUNDED objects are more

"neutral" permitted to

impossible for all paths

it to get

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neutral and you just

spek for yourself white man...I tttouuch hott allll the time.
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Well, I have heard the sotries of the "old timers" who would quitely touch a "hot" wire and determine the voltage and PHASE!

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quitely touch a

Nahhh... you could pick out the stinger that way..but I dont think eyeball spin alone would not give you phase on pure voltage... how is that done. Do you use the apprentice at all?
I myself after using a meter, and sometimes if there is not one in my ass pocket at the time, will kill the circuit then test for live ones with my finger...but I try to make sure my cigar is out at the time.
Phil Scott

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John Gilmer wrote: "Well, I have heard the sotries of the "old timers" who would quitely touch a "hot" wire and determine the voltage and PHASE!"
BULLSHIT!!!
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"old timers" who would quitely touch a

Not bullshit... I dont go after trying to find a stinger that way but no doubt some have... I have routinely gone after hot wire in a bundle by first making sure my feet are dry and that one hand is in my back pocket then NOT touching the hot wire straight on, but brushing past it, touching it that way, in a sweeping motion. that provides the momentum to take your hand past the contact before the nervous system can be frozen holding you in contact.
Ive seen many people do that... the last final check before plunging hard core with solid contact into a potentially hot area... I DO NOT do it close to the mains...or on anything over 240 volts however.
Id bet at least half the techs posting the NG have done this.
Phil Scott

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Snip

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| (first name) at ipal.net | http://phil.ipal.org/ http://ka9wgn.ham.org/ |
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The basic principal of electrical safety is that it must take at least two failures to introduce a hazard. The neutral is a current carrying conductor that is insulated. It is no longer permissible to use the neutral to ground the exposed metallic frames of appliances or other non current carrying metal parts of the electrical system. So there is no exposure to neutral contact. The voltage on the neutral is far less than the thirty volts it takes to break through a healthy humans skin resistance. In order for the shock hazard to exist a failure must occur in the continuity of the neutral so that it's voltage would rise to the service voltage AND the insulation would have to fail in a way that exposed you to contact. With the motor frames and all metallic enclosures grounded via the Equipment Grounding Conductor (EGC) there are three failures between you and a shock. Given the purpose of the US NEC that is considered sufficient.
90.1 Purpose. (A) Practical Safeguarding. The purpose of this Code is the practical safeguarding of persons and property from hazards arising from the use of electricity.
The reason that GFCIs are used to protect spa users is that the voltage drop on the EGC might well be over thirty volts under a fault condition that involves an ungrounded conductor. The likelihood of that being true for a neutral fault condition is far lower.
There is nothing stopping you from installing a three pole breaker with a shunt trip coil and a ground fault detector to raise the level of safety even higher. Alternatively you could use a contactor to energize the circuit with the contactors coil current supplied via a ground fault detection circuit. A three pole contactor would open all of the current carrying conductors including the neutral. -- Tom H
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| The basic principal of electrical safety is that it must take at least | two failures to introduce a hazard. The neutral is a current carrying | conductor that is insulated. It is no longer permissible to use the | neutral to ground the exposed metallic frames of appliances or other non | current carrying metal parts of the electrical system. So there is no | exposure to neutral contact. The voltage on the neutral is far less than
But that same logic, neither of the hot wires poses a risk, either. Then in that case, we don't need GFCI in the kitchen or bathroom because the grounded frame will protect us. But in reality, any of these wires can get in contact with water if an appliance is dropped in the sink.
| the thirty volts it takes to break through a healthy humans skin
Human skin does not exhibit a fixed voltage drop. A mere 6 volts can get the current up to the painful level, depending on various conditions such as skin moisture. For some people, like elderly, it can even kill at these current levels (5 ma). This is why the GFCI settings are in this range. And 6 volts can be present on the neutral.
| resistance. In order for the shock hazard to exist a failure must occur | in the continuity of the neutral so that it's voltage would rise to the
It only needs to be an imbalanced load with some significant length of neutral wire run.
| service voltage AND the insulation would have to fail in a way that
Don't need an insulation failure for this to happen. It can happen with normal wiring.
| exposed you to contact. With the motor frames and all metallic | enclosures grounded via the Equipment Grounding Conductor (EGC) there | are three failures between you and a shock. Given the purpose of the US | NEC that is considered sufficient.
Only 1 failure to reach a level hazardous to some people.
| The reason that GFCIs are used to protect spa users is that the voltage | drop on the EGC might well be over thirty volts under a fault condition | that involves an ungrounded conductor. The likelihood of that being | true for a neutral fault condition is far lower.
No guarantee that a fault is going back to the EGC first. The person might be in series with that path.
| There is nothing stopping you from installing a three pole breaker with | a shunt trip coil and a ground fault detector to raise the level of | safety even higher. Alternatively you could use a contactor to energize | the circuit with the contactors coil current supplied via a ground fault | detection circuit. A three pole contactor would open all of the current | carrying conductors including the neutral.
It would not be UL listed.
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wrote:

How do you arrive at 6 volts on a neutral? Even a fully loaded 30A service to a sub-panel 100 ft from the main panel does not result in 4 volts.

The imbalanced load, in combination with the length of the neutral wire, must develop enough voltage to be hazardous. How long a wire at what loading would be needed for 6 VAC???
<snip>

how would this happen???
daestrom
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Replies are in line.
snipped-for-privacy@ipal.net wrote:

In contact with the water is not the same as inside the human being. An adult in good health would be safe from anything the neutral would expose them to and a modern GFCI receptacle opens the neutral anyway. Getting back to your hot tub breaker there may not be a neutral to the hot tub but if there is it will only serve 120 volt pumps that have no exposure to contact. In addition the controls on a listed hot tub are mechanically operated not by direct electrical switching.

For six volts to be present on the neutral there has to be a high resistance connection or other resistive fault on the neutral. For the human being to make contact with that potential there has to be an additional failure in the neutral, a code violation in the placement of a receptacle, or an extension cord in use by a Darwin Award candidate.

How?
Describe it.

Under what circumstances?

In that statement you are plain wrong. There are combinations of contactor and ground fault detectors that are listed as type A GFCIs. That is in fact the standard method for protecting the larger commercial therapeutic hot tubs that are used in rehab centers and hospitals. -- Tom H
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candidate.
Yes yes...I see you have mentioned the awards..but have not provide a link. Many people are not familiar with this organization and could benefit with application information.
Have the published this years winners yet?
Phil Scott
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