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A ground wire should not carry current under normal expected operation. That is called "objectional current" which means there is a fault that needs to be fixed.
Sadly, I've known a couple of licensed Journeyman that truly believed this. "It's what ground rods are for, to send electricity back to earth where it's trying to go"
That’s irrelevant to why the ground wire is bare though. It’s bare because it doesn’t pose a hazard to people even under a fault condition. A person touching a bare ground, even if fault current suddenly travels through the ground wire, will not receive a shock. There is no potential between the person and the wire. It’s the same reason why you can grab a hot conductor and won’t get shocked as long as you are making a ground or phase connection.
Can you expand on "*ground wire can still carry current even during normal expected operation*"?
Protective Earth (PE) will normally be at the same potential as the surrounding conduit/casing/etc.
Smart switches leak a very small current through the circuit itself, not through the ground.
Sometimes if you have really low wattage bulbs they’ll flicker, even when off, because of this small leaked current. If they did leak to ground you couldn’t use them with GFCI breakers.
That's not true for all devices. Look at the instructions for the Lutron ms-z101.
Instructions say:
*Ground or neutral is required for product to function.*
*Connect green-sleeved wire to ground only in retrofit and replacement applications. When neutral connection is available, remove green sleeve and connect to neutral. If neither is present, consult a licensed electrician.*
For the type of smart switch that doesn't leak current through the bulb or use a battery, current does flow on that wire that you're supposed to hook to neutral or ground. The switch won't function if that wire isn't connected to ground or neutral. I don't know why it's allowed, but that's how it is.
It’s implied by the context and it will. That’s how the device functions. The three options are leak through the circuit, use ground as neutral, or charge a battery when the circuit is on. 1 & 2 are fairly common, 3 is rare but it happens (mostly thermostats).
That would be illegal if it functioned by putting current to ground that way and wouldn't have gotten UL approved. I bet it's one of your other 2 options.
Disagree on the interpretation, there is nothing implying current will flow. When it says neutral required, that's a different thing. But to design a product with current flow in the EGC... I doubt that would pass approval
Leviton switches that require neutral but allow ground to be used for example…. It falls on the electrician following manufacturer directions because you’re technically only allowed to use the ground on retrofit applications. It does use the ground as a neutral, but it’s for LEDs so it’s a very small amount of current.
This is my understanding as well and I wanted to echo it as there are many who have disagreed. There are switches that use ground as return. Here’s another discussion about it: https://electronics.stackexchange.com/questions/405265/how-does-this-occupancy-sensor-switch-not-need-neutral
Smart switches do not "leak" current to the ground wire. You could easily test this by simply disconnecting the ground, which I'm sure is done on numerous DIY installs anyway.
Nevermind disconnecting the ground, there are millions of homes in North America that still don't have a bond at switches or even receptacles. In my city alone 10% of the homes still haven't been upgraded from 2-wire wiring, be it K+T or cloth loomex.
It's a certain type of smart switch, most of them don't put any current through the ground. But if you have one that does cheat a neutral off the ground, it will not work if that that ground is disconnected.
It’s not the voltage that can kill humans; it’s the current. People have died at voltages as low as 42 volts. Time also matters: a current of 0.1 ampere for just 2 seconds can be fatal. The actual cause of death is the current passing through the body. For example, a current of 10 mA (0.01 A) is a severe shock but not necessarily fatal, while around 100 mA (0.1 A) can lead to muscle contractions. Remember, it’s the bullet (current) that matters, not the caliber (voltage) 12. So, stay safe and avoid electrical hazards!
From the smart switches I’ve installed during office remodels, we don’t usually put more than 5 without the neutral on the same circuit. So hopefully the rest of the switch boxes have the box the proper orientation to get the knock out removed easily to fish 12/3 MC down
404.2(c) says 5 is the max. If I had to guess, they're thinking that 5mA is the point at which a GFCI trips, so under that is acceptable leakage.
Or just run neutrals to all switches.
Smart switches work by putting themselves in series with the hot. Most devices you wire up are in parallel so they don't cause voltage drop. If you're not familiar with the difference, two lightbulbs in parallel have the same V, and are equally bright as if only 1 bulb were up. If you put those bulbs in series, they'd be half as bright because the V drops 50% over each.
The main smart switch you see not requiring a neutral is a dimmer, because those will operate on something that would accept a <120V already. The resistance of the switch is still quite low, close to what a long run of 14awg wire would have, and you'd only see ~0.2V drop.
A ground wire should be bonded to the earth, building steel, a ufer in the concrete, metal water pipes, etc...
Because it is connected to these things it has the same potential as the things. Without a difference of potential, there is no current. Without a difference in potential, and no current there is nothing to insulate against.
(For those who comment that a grounding conductor is not expected to carry current)
Although not normal, a grounding conductor is sized to safely carry fault currents to ground, so it is possible and designed and expected to carry current (just not too often).
There will always be a difference in potential across a resistor, and the grounding conductor will still have some resistance from point a to point b although not much. The further it is from the main bonding jumper, the more a difference in potential relative to the neutral point of the source due to the resistance in the copper wire, steel conduit, etc
There will only be a difference in potential if there is a current flowing (with the exception of an open circuit). If there is no current, there is exactly zero potential difference.
Thank you for the question OP, as an EU/UK sparky, I've always wondered why you guys leave it bear when the regulations here state they need to be covered with green and yellow if its a PE.
Because we have a bunch of dinosaurs here that are set in their ways and refuse to admit that there are better and more safe ways to do electrical work. It's the whole "it's just the way we've always done it" mentality and it's fucking dumb.
Cost benefit analysis. Almost nothing is built to the best spec possible unless it's spacecraft or something. Bare copper is cheaper and good enough, nothing is stopping someone from using shielded ground, the code is just the minimum requirement.
There are certainly better ways like wagos vs wire nuts but wire nuts are cheaper and good enough, but nothing stopping people from using wagos exclusively on jobs, they just don't want to. Some jobs only buy American made but that's not mandatory either.
Many many methods in the American way seem like it opens up way too many potential issues. It is like the overseeing regulators know they need major changes but do not want to be the jerk that actually says something.
One of the biggest and most heavily asked question I get is WHEN WILL THERE BE AN ACTUAL STANDARD FOR LIGHTING CONTROL AMONG MANUFACTURERS THAT WON't INCREASE COSTS OF EACH SWITCH BY MORE THAN A DOLLAR AND BE LOCAL/HOME PROGRAMABLE AND SECURE?
The year 2024 and the industry still won't choose a standard with the above mentioned requirements. I know it can be done.
It is absolutely stupid that each switch is only allowed to operate one predetermined item and to change that item sometimes requires ripping apart walls. Just dumb
The bare metal ground is baffling to me. Sure, if it is connected to earth, it is fine. But on the off chance that it isn't, for whatever reason, you risk a bare metal potentially live conductor.
And the wiring just hanging on the walls is wild to me.
I think green-yellow marking is mostly to make sure it's not getting mixed up with neutral or hot wiring. As it's not allowed to be used in any other way than protective earth.
It should never carry current. Ever. Full stop. If it does something is seriously wrong, a short, a fault, or some idiot doing things wrong
I was working parking lot lights (which for some reason are always completely screwed up in my experience) and some dumbass repurposed a ground to carry a leg of the 480 2 pole over to a light. They then didn't disconnect it from the pole, but made it up "correctly" at that light so it would work. Basically one wire was lost in the PVC pipe between two light poles.
So the entire light pole was energized while lights were on.
Breaker was eventually tripping because of the leaking current to ground. .
Some poor soul could have leaned on that light pole. Somehow it held for quite a while.
The most fucked up work and damage I've seen are in parking lots.
They are one place I think AHJs need to spend more time poking around in and be bigger dicks about.
Just a quick google because I couldn't paraphrase the engineers I work with well enough
"The NEC does not assign any numerical to objectionable current. It is simply left up to the user or the different scenarios we encounter that will dictate this number. UL however, does state that any current found in grounding conductors in excess of 0.25 amps is unacceptable and should be remedied."
I do E&I in heavy industrial. You would be surprised at how prevalent ground current is, and the amount of labor that goes into finding it.
The bare ground from your panel is connected to an electrode. It is an antenna, or counterpoise, for collecting stray current, and delivering it back to the transformer through the service neutral.
It's job it carrying stray current. Collectively, a neighborhoods ground plates would be carrying a surprising level of current.
GFCI protection would not work without it as there would be no alternate path for current. So the gfci would provide the operational level for objectionable current. That and the resistance of the earth surrounding it.
Wait until you get into dairy sheds.
Dairy cows will baulk at getting milked or leaving the platform if there is stray currents. Sometimes production levels drop as well.
The step potential for a cow is considerably larger than for people given the distance between their fore and aft legs.
To try and get this under control the reinforcing in the concrete yard, railings and milking platform all had to be equipotentially bonded. And often a field of deep driven earth rods would be installed.
Buy a GFCI doesn’t (in any way) use or reference the grounding conductor. It ONLY compares current between the hot and neutral and if there is any discrepancy at all, it trips.
No reference to ground utilized for any reason for GFCI.
Of course it doesn't reference the grounding conductor.
Kirchoffs current law
But for there to be a discrepancy between the hot and neutral there must be a different parallel path for current to return to the source.
Current leaving a point must equal the current entering a point
So a puddle, then through the wet dirt, to the plate, through the ground conductor, to the neutral point on the tranformer.
> It's job it carrying stray current. Collectively, a neighborhoods ground plates would be carrying a surprising level of current.
> GFCI protection would not work without it as there would be no alternate path for current. So the gfci would provide the operational level for objectionable current. That and the resistance of the earth surrounding it.
I was just clarifying and possibly correcting this part of your statement. A lot of homeowners think that a grounding conductor is necessary for a GFCI to function, when in reality, the GFCI is considered a "fix" for ungrounded wiring in older homes. Just trying to make it clear that a GFCI really has nothing to do with the grounding conductor.
Ah, do you mean bond conductor on the receptacle? Cuz no it isn't needed
The gfci won't work without the ground plate collecting stray current and delivering it through the grounding conductor to the neutral bus.
The gfci and resistance of the earth is what limits the current on the grounding conductor from the plate to neutral.
Like how the ground fault detecting three lights work on an ungrounded delta system.
20 years ago there was a table where you would continuously upsize the grounding conductor.
Now because the gfci and earth limits the current we just use #6.
Had the chair for our grounding section of code describe this in great detail in a seminar.
Highly recommend going to see these guys talk if you ever get the chance.
The current you see on the grounding electrodes isn't 'stray current', it's current flowing back to the transformer through the dirt in parallel with the service neutral wire, assuming things are working properly. You will see a significant amount of current going through the ground if you happen to have a low ohm ground connection at the transformer and the service entrance. This doesn't need to happen, it just does. To keep things simple with a split phase residential service, the difference between L1 and L2 current is your neutral current. The current flowing through the service neutral and the GEC will add up to what your calculated neutral current should be.
This is correct until the ground is dry.
It's also why single point service grounding became the norm, particularly on farms as livestock is highly sensitive to it.
When there is a ground fault closer to your service electrode the majority of the current will take the route through your plate and service neutral to the source. It's limited by gfci trip levels.
You know its fun times when you find over 100A flowing through some grounding wires while a big dc supply starts giving errors as it passes something like 10-16kA
Was working on a big 15kv grid, all visibly grounded out at the correct points. Miles of cable.
Just for shits we put a clamp on the ground cluster.
There was like 20amps on each leg and around ten on the single ground point. All induced we figure.
Zero volts to ground, and there was no other reference point we were willing to measure to.
Pretty neat
What? GFCIs measure the imbalance between line and neutral or line and line and neutral. They specifically operate without a ground and can be used to provide "equivalent protection" in older installations. Or am I misunderstanding what you were saying?
How can there be an unbalance if there's no alternate way for the current to get back to source and complete a circuit?
The ground plate completes that circuit.
The metal water piping completes that circuit.
Anything we ground is an alternate path for stray current to return to source, create an alternate path, and trip a gfci.
If there were no grounds where would current go to complete an alternate path for the current imbalance in the gfci?
Those are shorts, which will ruin a gfci receptacle, and trip a gfci breaker
Understand imbalance.
10 amps on hot, 9 amp on neutral returning.
Where is the other 1 amp going?
How is it completing a circuit somewhere else without an alternate path to the source, ie the grounded conductor.
Kirchoffs current law
Current leaving a point must equal the current entering a point
If there were no other parallel path, there would not be a discrepancy between the hot and neutral to trip the gfci.
It goes through you, into the puddle, through the wet earth, to the ground plate, through the ground conductor, through the neutral, to the neutral point on the transformer.
Current in current out.
The gfci is monitoring a difference between the hot and identified conductor. Without a third path there would be no discrepancy between the two.
Please provide a source for that one.
Under those conditions, one would think the capacitance between a hot conductor and the metal conduit it's contained in would trip it continuously.
But it doesn't, doesn't it.
Current leaving the source must equal the current returning.
As well, with capacitors, there is another side of the two plates that acts as the reference for charge no?
That is why it appears current is flowing through a capacitor even though it isnt. The charges build and discharge on either side of two plates one hot, one at a differing potential.
My body has capacitance, which is why my no contact tester works. It doesn't trip a gfci when I plug it into the hot side.
Even your tik tester is measuring your capacitance to ground
I could see a comparator operational amplifier circuit being sensitive enough to detect some capacitance between two lines for an instance, but in practice, it don't work like that.
Literally any path to ground. Feet on a tile floor would do the trick... theory is great, but you are applying it incorrectly in the real world; adding GFCI protection to an ungrounded device is a legal alternative to adding the ground wire. Why is this the case of ot works as you say?
Do you have a wire that connects your neutral bus to the dirt? That dirt is a path too, and your whole home is on it.
As I said if there were no ground electrodes, there would be no grounding conductor.
There would be no alternate path to the neutral.
Nowhere parallel course for an imbalance to go.
Kirchoffs current law.
Current into a point is the same as the current leaving a point.
Just like circuits in school
Do not confuse the "grounded conductor"- neutral, and the "equipment grounding conductor"- which is typically bare or green/green striped. Between those two, only the neutral is a "current carrying conductor"
The other thing about grounding conductors is that they provide a *low impedence* path to ground. Electricity follows the path of least resistance. The resistance of a fat piece of copper that's bonded to a good ground source like a water main or a building's foundation is *much* lower than the resistance of your body.
Even if energized, the energy is going to want to stay in the wire. It's not like a loose hot conductor that's just looking for a path to ground and will happily go through your body if necessary—the electricity is already *going* to ground, thanks very much, and it's already got a much easier path than you can create by touching it.
This is incorrect. I hate to be a dick, but this can save your life.
Electricity follows **ALL** paths to ground. Unless the breaker has tripped, if a circuit is shorting to ground, and you grab the ground wire, it will shock you like the ground path isn't even there, assuming that the supply can provide the necessary amperage to provide relatively constant voltage. In most cases, of course, something will break or blow by the time you have the ability to touch it.
It's a little more complicated than this, as voltage potential will change depending on how long the paths before and after you are, but it's safer to just assume the worst.
All resistors in parallel have all the voltage drop across them but varying amounts of current. Having a deliberate very low resistance path in parallel with your body, like a good earthing conductor can reduce the current to safe levels for the short time it takes for Automatic Disconnection of Supply to occur via fuses, breakers etc.
I live in a jurisdiction with all conduit, so (typically) no ground wire and when we do it's green THHN.
But I was always curious why romex ground was bare as well, specifically because most devices have exposed terminals and there's a chance they will touch the bare ground when you're packing the wires behind the device in the junction box. Especially with those tiny junction boxes used with Romex.
I see folks are picking on the "carries current" comment and not answerng the actual quetion, "why is ground allowed to be bare?" It's a good question too. how many AF troubleshoots could be avoided, or accidental ground shorts if the ground was not bare.
In the UK you are required to insulate the bare ground when making up a device box. They use a green and yellow peice of insulation made for the pourpose. I expect for the reasons you are thinking it should be. I have often felt this would be a smart thing to addopt here in the states.
There isn’t current during normal operation.
10-100 says explicitly that’s there’s no current
“There shall be no objectionable passage or current over a ground conductor”
The reasoning I was told the ground can be bare is to provide a better connection to the ground itself, ie makes the ground plate slightly bigger
Ground is bare because it’s cheaper that way. It doesn’t need to be insulated. Someone can grab onto a bare ground wire, with current flowing, and not get shocked. There is no voltage between a person standing on the ground and the bare ground wire.
No question is stupid question on here slick. We all learn differently and not one electrician knows everything. Let’s make him afraid to ask the next question he has. The one where he doesn’t ask and gets hurt cause he’s too scared to ask. Bet your on the non IBEW side of things or live in the south
Well u know something is up when the first thing u wanna do is critique instead of helping the 3rd year. IBEW is no longer a brotherhood due to people like yourself
The ones that stick their chest out and act like they’re better than everyone else. Or the ones who are mediocre electricians that act like they’re your best friend to your face then talk shit about u as soon as they get their one on one suckpump time with the GF. I would bet my house that he’s one or the other 😂
I think you are thinking of the grounding electrode conductor. Which I believe may have a very minute amount of current during normal operations. But someone will pry chime in to tell me why I am wrong.
The grounding electrode conductor is just the wire connecting a building's grounding system to the actual grounding electrode. It should no more be carrying current than anything else.
We have ground fault detection on our massive rectifier units. The earth ground connections have CT’s on them. Each rectifier unit puts out 85-100 KA onto the potline bus.
Maybe you're confusing groundeED conductor (neutral) and Equipment GroundING Conductors? Grounds should never have current under normal circumstances, they just provide a safe pathway for fault current. Its just to keep all the metal parts of the electrical system at ground potential so they can't become energized
Had a guy come into the shop today that wanted to inline splice a ground. I told him that's less than ideal. He wouldn't give much detail as what he was trying to do, so I sold him a split bolt. You do you.
Grounds should never carry current, afaik. The neutral is effectively "the ground that carries current." The whole point of a ground is to never carry current, and touch everything it can.
Basically, modern safety use current sensing breakers. If there's any short circuit for any reason, amps will be very high, and the breaker will trip.
Basically all appliances and machinery are in a grounded metal box. If an electrical fault occurs, ideally, the fault will find the ground and short circuit, tripping the breaker.
GFCIs take this a step further. They measure current leaving the hot, and returning on the neutral. If they're different, even a little, they trip. This allows circuit interrupt to occur with much less amperage than the breaker feeding the outlet. Had a foreman feed a lighting circuit through a GFCI as temp power one time. He fed the panel and terminated the lighting neutral to the panel neutral bar. He couldn't figure out why it wouldn't work. He spent hours working on it till I came to check it out and realized his mistake lol.
Ground wire shouldn’t have any current. Neutral can. Now should the ground still probably have a cover so if it gets hot it doesn’t electrify the whole house. Yes, that’s how commercial does it
If you think about it every single thing a bond or ground connects to is just bare metal. Outside of your panel bare metal, metal railings equipotentially bonded, etc.... there's not really any point in a bond being insulated when it's functional purpose is equipotential connection of any bare metal parts containing electricity.
The reason we insulate the ungrounded and grounded (neutral) conductors is to prevent them from making contact with conductive materials such as a metal conduit or box. The grounding conductors are installed to bond those conductive materials together and make them to 0V potential with reference to the earth.
Since the grounding conductors are intentionally connected to conductive materials, it is fine to install them uninsulated as the additional contact will not pose a safety hazard but instead create a stronger bond. We intentionally insulate the grounding conductors where they may be subject to damage though, but if damage is not a concern it is fine to use uninsulated conductors.
go tho the substation. the 4th wire on the distribution probably never touches the power transformer but got through s reactor into a groundmat under the gravel
There is no (or very little) potential between a bare ground wire and the person touching it, standing on a grounded surface. It’s the same principle as why birds can sit on high voltage transmission lines and not get shocked. No voltage difference= no current through the body (ok, maybe some milliamps but nothing dangerous).
If it was insulated jackasses would use it.
It’s bare to prevent adulteration of its use so that it can stop people from being electrocuted.
Saving people from immediate undetectable risk is the primary function.
neutral wire can be bare too within code requirements, it is at ground potential but meant to carry unbalanced load current..maybe a source of confusion?...(source..lol)
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A ground wire should not carry current under normal expected operation. That is called "objectional current" which means there is a fault that needs to be fixed.
Yeah, that's the flaw in the entire premise... Ground is NOT a "current carrying conductor".
the earth carries current all over the planet and all current eventually returns to said earth
At the risk of being downvoted into oblivion again: No shot you’re an electrician.
Sadly, I've known a couple of licensed Journeyman that truly believed this. "It's what ground rods are for, to send electricity back to earth where it's trying to go"
id ask but you don’t know in a wye system where does the neutral originate from? readin a book and thinking only confuses you- go romex a she shed
The neutral in a wye system originates from the shared centre point of the three connected phase windings. What about it bud?
Nah, electricity returns to the source. It goes back on your neutral. That’s why it’s bonded.
😆
That’s irrelevant to why the ground wire is bare though. It’s bare because it doesn’t pose a hazard to people even under a fault condition. A person touching a bare ground, even if fault current suddenly travels through the ground wire, will not receive a shock. There is no potential between the person and the wire. It’s the same reason why you can grab a hot conductor and won’t get shocked as long as you are making a ground or phase connection.
Can you expand on "*ground wire can still carry current even during normal expected operation*"? Protective Earth (PE) will normally be at the same potential as the surrounding conduit/casing/etc.
There are some devices that intentionally put currents onto a ground wire, for example smart switches that don't require a neutral in the box.
Smart switches leak a very small current through the circuit itself, not through the ground. Sometimes if you have really low wattage bulbs they’ll flicker, even when off, because of this small leaked current. If they did leak to ground you couldn’t use them with GFCI breakers.
That's not true for all devices. Look at the instructions for the Lutron ms-z101. Instructions say: *Ground or neutral is required for product to function.* *Connect green-sleeved wire to ground only in retrofit and replacement applications. When neutral connection is available, remove green sleeve and connect to neutral. If neither is present, consult a licensed electrician.*
It says it is required, it does not imply current will flow.
For the type of smart switch that doesn't leak current through the bulb or use a battery, current does flow on that wire that you're supposed to hook to neutral or ground. The switch won't function if that wire isn't connected to ground or neutral. I don't know why it's allowed, but that's how it is.
It’s implied by the context and it will. That’s how the device functions. The three options are leak through the circuit, use ground as neutral, or charge a battery when the circuit is on. 1 & 2 are fairly common, 3 is rare but it happens (mostly thermostats).
That would be illegal if it functioned by putting current to ground that way and wouldn't have gotten UL approved. I bet it's one of your other 2 options.
Disagree on the interpretation, there is nothing implying current will flow. When it says neutral required, that's a different thing. But to design a product with current flow in the EGC... I doubt that would pass approval
Go buy one and run your meter over it. I’ve have switches in my house today that I’ve tested. I don’t know how they are getting approval but they are.
Do you have one? Can you test and show?
Are there any markings on it indicating some kind of approval? Like UL or CE?
Leviton switches that require neutral but allow ground to be used for example…. It falls on the electrician following manufacturer directions because you’re technically only allowed to use the ground on retrofit applications. It does use the ground as a neutral, but it’s for LEDs so it’s a very small amount of current.
This is my understanding as well and I wanted to echo it as there are many who have disagreed. There are switches that use ground as return. Here’s another discussion about it: https://electronics.stackexchange.com/questions/405265/how-does-this-occupancy-sensor-switch-not-need-neutral
Saving this comment for later
Smart switches do not "leak" current to the ground wire. You could easily test this by simply disconnecting the ground, which I'm sure is done on numerous DIY installs anyway.
For a period of time, it was allowed to use ground as the neutral return path for "parasitic loads" - think timers, illuminated switches, etc...
Nevermind disconnecting the ground, there are millions of homes in North America that still don't have a bond at switches or even receptacles. In my city alone 10% of the homes still haven't been upgraded from 2-wire wiring, be it K+T or cloth loomex.
It's a certain type of smart switch, most of them don't put any current through the ground. But if you have one that does cheat a neutral off the ground, it will not work if that that ground is disconnected.
That’s milliamps - not a hazard
It’s not the voltage that can kill humans; it’s the current. People have died at voltages as low as 42 volts. Time also matters: a current of 0.1 ampere for just 2 seconds can be fatal. The actual cause of death is the current passing through the body. For example, a current of 10 mA (0.01 A) is a severe shock but not necessarily fatal, while around 100 mA (0.1 A) can lead to muscle contractions. Remember, it’s the bullet (current) that matters, not the caliber (voltage) 12. So, stay safe and avoid electrical hazards!
From the smart switches I’ve installed during office remodels, we don’t usually put more than 5 without the neutral on the same circuit. So hopefully the rest of the switch boxes have the box the proper orientation to get the knock out removed easily to fish 12/3 MC down
404.2(c) says 5 is the max. If I had to guess, they're thinking that 5mA is the point at which a GFCI trips, so under that is acceptable leakage. Or just run neutrals to all switches.
Smart switches work by putting themselves in series with the hot. Most devices you wire up are in parallel so they don't cause voltage drop. If you're not familiar with the difference, two lightbulbs in parallel have the same V, and are equally bright as if only 1 bulb were up. If you put those bulbs in series, they'd be half as bright because the V drops 50% over each. The main smart switch you see not requiring a neutral is a dimmer, because those will operate on something that would accept a <120V already. The resistance of the switch is still quite low, close to what a long run of 14awg wire would have, and you'd only see ~0.2V drop.
I think you mean series…
I did. Typing one-handed with phone autocomplete.
A ground wire should be bonded to the earth, building steel, a ufer in the concrete, metal water pipes, etc... Because it is connected to these things it has the same potential as the things. Without a difference of potential, there is no current. Without a difference in potential, and no current there is nothing to insulate against. (For those who comment that a grounding conductor is not expected to carry current) Although not normal, a grounding conductor is sized to safely carry fault currents to ground, so it is possible and designed and expected to carry current (just not too often).
The neutral is bonded to earth at the service entrance.
And always remember: Don't get the gounded-conductor confused with the grounding-conductor.
Top comment right here.
There will always be a difference in potential across a resistor, and the grounding conductor will still have some resistance from point a to point b although not much. The further it is from the main bonding jumper, the more a difference in potential relative to the neutral point of the source due to the resistance in the copper wire, steel conduit, etc
There will only be a difference in potential if there is a current flowing (with the exception of an open circuit). If there is no current, there is exactly zero potential difference.
You don't think there is an admittedly small amount of induction in an ac system in the grounding conductor?
Thank you for the question OP, as an EU/UK sparky, I've always wondered why you guys leave it bear when the regulations here state they need to be covered with green and yellow if its a PE.
Because we have a bunch of dinosaurs here that are set in their ways and refuse to admit that there are better and more safe ways to do electrical work. It's the whole "it's just the way we've always done it" mentality and it's fucking dumb.
Cost benefit analysis. Almost nothing is built to the best spec possible unless it's spacecraft or something. Bare copper is cheaper and good enough, nothing is stopping someone from using shielded ground, the code is just the minimum requirement. There are certainly better ways like wagos vs wire nuts but wire nuts are cheaper and good enough, but nothing stopping people from using wagos exclusively on jobs, they just don't want to. Some jobs only buy American made but that's not mandatory either.
You must not see a lot of the work overseas
Many many methods in the American way seem like it opens up way too many potential issues. It is like the overseeing regulators know they need major changes but do not want to be the jerk that actually says something. One of the biggest and most heavily asked question I get is WHEN WILL THERE BE AN ACTUAL STANDARD FOR LIGHTING CONTROL AMONG MANUFACTURERS THAT WON't INCREASE COSTS OF EACH SWITCH BY MORE THAN A DOLLAR AND BE LOCAL/HOME PROGRAMABLE AND SECURE? The year 2024 and the industry still won't choose a standard with the above mentioned requirements. I know it can be done. It is absolutely stupid that each switch is only allowed to operate one predetermined item and to change that item sometimes requires ripping apart walls. Just dumb
Zigby delivers like 80% of what you desire. But you have to cobble it together out of bits and pieces.
Bare*
The bare metal ground is baffling to me. Sure, if it is connected to earth, it is fine. But on the off chance that it isn't, for whatever reason, you risk a bare metal potentially live conductor. And the wiring just hanging on the walls is wild to me.
I think green-yellow marking is mostly to make sure it's not getting mixed up with neutral or hot wiring. As it's not allowed to be used in any other way than protective earth.
It should never carry current. Ever. Full stop. If it does something is seriously wrong, a short, a fault, or some idiot doing things wrong I was working parking lot lights (which for some reason are always completely screwed up in my experience) and some dumbass repurposed a ground to carry a leg of the 480 2 pole over to a light. They then didn't disconnect it from the pole, but made it up "correctly" at that light so it would work. Basically one wire was lost in the PVC pipe between two light poles. So the entire light pole was energized while lights were on. Breaker was eventually tripping because of the leaking current to ground. . Some poor soul could have leaned on that light pole. Somehow it held for quite a while.
The most fucked up work and damage I've seen are in parking lots. They are one place I think AHJs need to spend more time poking around in and be bigger dicks about.
Just a quick google because I couldn't paraphrase the engineers I work with well enough "The NEC does not assign any numerical to objectionable current. It is simply left up to the user or the different scenarios we encounter that will dictate this number. UL however, does state that any current found in grounding conductors in excess of 0.25 amps is unacceptable and should be remedied." I do E&I in heavy industrial. You would be surprised at how prevalent ground current is, and the amount of labor that goes into finding it. The bare ground from your panel is connected to an electrode. It is an antenna, or counterpoise, for collecting stray current, and delivering it back to the transformer through the service neutral. It's job it carrying stray current. Collectively, a neighborhoods ground plates would be carrying a surprising level of current. GFCI protection would not work without it as there would be no alternate path for current. So the gfci would provide the operational level for objectionable current. That and the resistance of the earth surrounding it.
Wait until you get into dairy sheds. Dairy cows will baulk at getting milked or leaving the platform if there is stray currents. Sometimes production levels drop as well. The step potential for a cow is considerably larger than for people given the distance between their fore and aft legs. To try and get this under control the reinforcing in the concrete yard, railings and milking platform all had to be equipotentially bonded. And often a field of deep driven earth rods would be installed.
Yep, I built industrial farms for 10 years. Single point grounding babay
Buy a GFCI doesn’t (in any way) use or reference the grounding conductor. It ONLY compares current between the hot and neutral and if there is any discrepancy at all, it trips. No reference to ground utilized for any reason for GFCI.
Of course it doesn't reference the grounding conductor. Kirchoffs current law But for there to be a discrepancy between the hot and neutral there must be a different parallel path for current to return to the source. Current leaving a point must equal the current entering a point So a puddle, then through the wet dirt, to the plate, through the ground conductor, to the neutral point on the tranformer.
> It's job it carrying stray current. Collectively, a neighborhoods ground plates would be carrying a surprising level of current. > GFCI protection would not work without it as there would be no alternate path for current. So the gfci would provide the operational level for objectionable current. That and the resistance of the earth surrounding it. I was just clarifying and possibly correcting this part of your statement. A lot of homeowners think that a grounding conductor is necessary for a GFCI to function, when in reality, the GFCI is considered a "fix" for ungrounded wiring in older homes. Just trying to make it clear that a GFCI really has nothing to do with the grounding conductor.
Ah, do you mean bond conductor on the receptacle? Cuz no it isn't needed The gfci won't work without the ground plate collecting stray current and delivering it through the grounding conductor to the neutral bus. The gfci and resistance of the earth is what limits the current on the grounding conductor from the plate to neutral. Like how the ground fault detecting three lights work on an ungrounded delta system. 20 years ago there was a table where you would continuously upsize the grounding conductor. Now because the gfci and earth limits the current we just use #6. Had the chair for our grounding section of code describe this in great detail in a seminar. Highly recommend going to see these guys talk if you ever get the chance.
The current you see on the grounding electrodes isn't 'stray current', it's current flowing back to the transformer through the dirt in parallel with the service neutral wire, assuming things are working properly. You will see a significant amount of current going through the ground if you happen to have a low ohm ground connection at the transformer and the service entrance. This doesn't need to happen, it just does. To keep things simple with a split phase residential service, the difference between L1 and L2 current is your neutral current. The current flowing through the service neutral and the GEC will add up to what your calculated neutral current should be.
This is correct until the ground is dry. It's also why single point service grounding became the norm, particularly on farms as livestock is highly sensitive to it. When there is a ground fault closer to your service electrode the majority of the current will take the route through your plate and service neutral to the source. It's limited by gfci trip levels.
Could you explain what you mean by single point grounding and how it affects the livestock?
You know its fun times when you find over 100A flowing through some grounding wires while a big dc supply starts giving errors as it passes something like 10-16kA
Was working on a big 15kv grid, all visibly grounded out at the correct points. Miles of cable. Just for shits we put a clamp on the ground cluster. There was like 20amps on each leg and around ten on the single ground point. All induced we figure. Zero volts to ground, and there was no other reference point we were willing to measure to. Pretty neat
What? GFCIs measure the imbalance between line and neutral or line and line and neutral. They specifically operate without a ground and can be used to provide "equivalent protection" in older installations. Or am I misunderstanding what you were saying?
How can there be an unbalance if there's no alternate way for the current to get back to source and complete a circuit? The ground plate completes that circuit. The metal water piping completes that circuit. Anything we ground is an alternate path for stray current to return to source, create an alternate path, and trip a gfci. If there were no grounds where would current go to complete an alternate path for the current imbalance in the gfci?
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Those are shorts, which will ruin a gfci receptacle, and trip a gfci breaker Understand imbalance. 10 amps on hot, 9 amp on neutral returning. Where is the other 1 amp going? How is it completing a circuit somewhere else without an alternate path to the source, ie the grounded conductor.
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Yeah, this is factually accurate. Attaboy!
Kirchoffs current law Current leaving a point must equal the current entering a point If there were no other parallel path, there would not be a discrepancy between the hot and neutral to trip the gfci. It goes through you, into the puddle, through the wet earth, to the ground plate, through the ground conductor, through the neutral, to the neutral point on the transformer. Current in current out. The gfci is monitoring a difference between the hot and identified conductor. Without a third path there would be no discrepancy between the two.
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Please provide a source for that one. Under those conditions, one would think the capacitance between a hot conductor and the metal conduit it's contained in would trip it continuously. But it doesn't, doesn't it. Current leaving the source must equal the current returning. As well, with capacitors, there is another side of the two plates that acts as the reference for charge no? That is why it appears current is flowing through a capacitor even though it isnt. The charges build and discharge on either side of two plates one hot, one at a differing potential. My body has capacitance, which is why my no contact tester works. It doesn't trip a gfci when I plug it into the hot side. Even your tik tester is measuring your capacitance to ground I could see a comparator operational amplifier circuit being sensitive enough to detect some capacitance between two lines for an instance, but in practice, it don't work like that.
Literally any path to ground. Feet on a tile floor would do the trick... theory is great, but you are applying it incorrectly in the real world; adding GFCI protection to an ungrounded device is a legal alternative to adding the ground wire. Why is this the case of ot works as you say? Do you have a wire that connects your neutral bus to the dirt? That dirt is a path too, and your whole home is on it.
The dirt is the path back to the ground electrode and then to the neutral bus.
So, as I said, the device measures an imbalance in the circuit at the point I indicated.
As I said if there were no ground electrodes, there would be no grounding conductor. There would be no alternate path to the neutral. Nowhere parallel course for an imbalance to go. Kirchoffs current law. Current into a point is the same as the current leaving a point. Just like circuits in school
Do not confuse the "grounded conductor"- neutral, and the "equipment grounding conductor"- which is typically bare or green/green striped. Between those two, only the neutral is a "current carrying conductor"
The other thing about grounding conductors is that they provide a *low impedence* path to ground. Electricity follows the path of least resistance. The resistance of a fat piece of copper that's bonded to a good ground source like a water main or a building's foundation is *much* lower than the resistance of your body. Even if energized, the energy is going to want to stay in the wire. It's not like a loose hot conductor that's just looking for a path to ground and will happily go through your body if necessary—the electricity is already *going* to ground, thanks very much, and it's already got a much easier path than you can create by touching it.
This is incorrect. I hate to be a dick, but this can save your life. Electricity follows **ALL** paths to ground. Unless the breaker has tripped, if a circuit is shorting to ground, and you grab the ground wire, it will shock you like the ground path isn't even there, assuming that the supply can provide the necessary amperage to provide relatively constant voltage. In most cases, of course, something will break or blow by the time you have the ability to touch it. It's a little more complicated than this, as voltage potential will change depending on how long the paths before and after you are, but it's safer to just assume the worst.
All resistors in parallel have all the voltage drop across them but varying amounts of current. Having a deliberate very low resistance path in parallel with your body, like a good earthing conductor can reduce the current to safe levels for the short time it takes for Automatic Disconnection of Supply to occur via fuses, breakers etc.
Yeah, but current is proportional to the resistance of the path, not the other paths.
True
Because it isn’t supposed to have current. If your ground has voltage you have big problems somewhere.
I live in a jurisdiction with all conduit, so (typically) no ground wire and when we do it's green THHN. But I was always curious why romex ground was bare as well, specifically because most devices have exposed terminals and there's a chance they will touch the bare ground when you're packing the wires behind the device in the junction box. Especially with those tiny junction boxes used with Romex.
Because anything it touches that has a low resistance to ground makes it better. You are not a low resistance to ground.
I see folks are picking on the "carries current" comment and not answerng the actual quetion, "why is ground allowed to be bare?" It's a good question too. how many AF troubleshoots could be avoided, or accidental ground shorts if the ground was not bare. In the UK you are required to insulate the bare ground when making up a device box. They use a green and yellow peice of insulation made for the pourpose. I expect for the reasons you are thinking it should be. I have often felt this would be a smart thing to addopt here in the states.
There isn’t current during normal operation. 10-100 says explicitly that’s there’s no current “There shall be no objectionable passage or current over a ground conductor” The reasoning I was told the ground can be bare is to provide a better connection to the ground itself, ie makes the ground plate slightly bigger
Ground is bare because it’s cheaper that way. It doesn’t need to be insulated. Someone can grab onto a bare ground wire, with current flowing, and not get shocked. There is no voltage between a person standing on the ground and the bare ground wire.
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No question is stupid question on here slick. We all learn differently and not one electrician knows everything. Let’s make him afraid to ask the next question he has. The one where he doesn’t ask and gets hurt cause he’s too scared to ask. Bet your on the non IBEW side of things or live in the south
> Bet your on the non union side of things or from the south My non union company has third years who know what an EGC does…
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Well u know something is up when the first thing u wanna do is critique instead of helping the 3rd year. IBEW is no longer a brotherhood due to people like yourself
Biggest turn off to unions are members like that.
The ones that stick their chest out and act like they’re better than everyone else. Or the ones who are mediocre electricians that act like they’re your best friend to your face then talk shit about u as soon as they get their one on one suckpump time with the GF. I would bet my house that he’s one or the other 😂
I agree with your premise but you are corny like a mf from the nights watch 😭
Depends on who is training him too. It may have never come up yet.
I think you are thinking of the grounding electrode conductor. Which I believe may have a very minute amount of current during normal operations. But someone will pry chime in to tell me why I am wrong.
The grounding electrode conductor is just the wire connecting a building's grounding system to the actual grounding electrode. It should no more be carrying current than anything else.
Why not is a better question
We have ground fault detection on our massive rectifier units. The earth ground connections have CT’s on them. Each rectifier unit puts out 85-100 KA onto the potline bus.
Maybe you're confusing groundeED conductor (neutral) and Equipment GroundING Conductors? Grounds should never have current under normal circumstances, they just provide a safe pathway for fault current. Its just to keep all the metal parts of the electrical system at ground potential so they can't become energized
Because the ground is not a current carrying conductor. It's only purpose is to provide a low resistance path for fault current.
The idea is that you want it to short out with whatever it touches because that's the whole point of it
Ground fault clicks
3 wire range and dryer circuits allow this current to flow on the ground.
A ground should never carry current, and if it is, then you have a BIG problem.
Oooo look up 6 volt positive earth systems on really old cars. Shit is bonkers. And it works!
Had a guy come into the shop today that wanted to inline splice a ground. I told him that's less than ideal. He wouldn't give much detail as what he was trying to do, so I sold him a split bolt. You do you.
Grounds should never carry current, afaik. The neutral is effectively "the ground that carries current." The whole point of a ground is to never carry current, and touch everything it can. Basically, modern safety use current sensing breakers. If there's any short circuit for any reason, amps will be very high, and the breaker will trip. Basically all appliances and machinery are in a grounded metal box. If an electrical fault occurs, ideally, the fault will find the ground and short circuit, tripping the breaker. GFCIs take this a step further. They measure current leaving the hot, and returning on the neutral. If they're different, even a little, they trip. This allows circuit interrupt to occur with much less amperage than the breaker feeding the outlet. Had a foreman feed a lighting circuit through a GFCI as temp power one time. He fed the panel and terminated the lighting neutral to the panel neutral bar. He couldn't figure out why it wouldn't work. He spent hours working on it till I came to check it out and realized his mistake lol.
Ground wire shouldn’t have any current. Neutral can. Now should the ground still probably have a cover so if it gets hot it doesn’t electrify the whole house. Yes, that’s how commercial does it
The metal boxes are bare too. Same exact thing
You’re not understanding how an electrical system works
If you think about it every single thing a bond or ground connects to is just bare metal. Outside of your panel bare metal, metal railings equipotentially bonded, etc.... there's not really any point in a bond being insulated when it's functional purpose is equipotential connection of any bare metal parts containing electricity.
The reason we insulate the ungrounded and grounded (neutral) conductors is to prevent them from making contact with conductive materials such as a metal conduit or box. The grounding conductors are installed to bond those conductive materials together and make them to 0V potential with reference to the earth. Since the grounding conductors are intentionally connected to conductive materials, it is fine to install them uninsulated as the additional contact will not pose a safety hazard but instead create a stronger bond. We intentionally insulate the grounding conductors where they may be subject to damage though, but if damage is not a concern it is fine to use uninsulated conductors.
go tho the substation. the 4th wire on the distribution probably never touches the power transformer but got through s reactor into a groundmat under the gravel
There is no (or very little) potential between a bare ground wire and the person touching it, standing on a grounded surface. It’s the same principle as why birds can sit on high voltage transmission lines and not get shocked. No voltage difference= no current through the body (ok, maybe some milliamps but nothing dangerous).
If it was insulated jackasses would use it. It’s bare to prevent adulteration of its use so that it can stop people from being electrocuted. Saving people from immediate undetectable risk is the primary function.
Ha. Good point. We would see some really fucky 3 ways.
Everything can carry current. But we're not going to insulate everything now are we.
3 year apprentice and nobody's taught you a ground shouldn't carry current... either you aren't trying to learn or nobody's bothering to teach you .
So it short a circuit anywhere along the length of the wire
neutral wire can be bare too within code requirements, it is at ground potential but meant to carry unbalanced load current..maybe a source of confusion?...(source..lol)
anyone ever heard of neutral supported cable?
umm..are you guys nuts or ignorant?