Low power on shop electrical circuit.

[bc]

In practice, it just provides me a little food for thought, mostly with respect to lightning. We have a couple of electric fence controllers, they can be literal "lightning rods," bringing lightning surges into your building's power, even if you have those surge arrestors on the wire.

Where ground rods are and how neutrals are done may affect my thinking about where to plug in the electric fence.

Yep. Lightning and someone sticking a monkey wrench inside your panel. When a rat chews through your wiring, you do your best James Cagney impression, "You Dirty Rat!!".

 

[will-max dairy]

PS to Wills great question above

RE my para 3. If a change were required by the utility or any local authority and if it was necessary to upgrade, all required to update to only having a single ng bond would be to un bond at those downstream panels making them true subs with separate insulated and isolated n and g busses. Easy peasey but dont do anything I say consult the nec or local professionals don’t risk the farm in anything posted here lay or professional me included !!!!

JT

This is also why, in my little corner of the world, where I have often lived in old places with old wiring... when I install a ground. It's always at least as big as the hot and neutral. If somebody pulled a stunt that, like you say, puts ground in parallel with neutral... I want as much copper in parallel with me to ground the neutral at the mains as possible... enough to trip every breaker to the pole..lol.

edit... I've played a little loose with terminology here. made a couple of edits to be more clear.

 

[olddavid]

Anyway, the meter connects to a panel on the placard. Inside the panel is a breaker for the house and a breaker for the barn; which could be the "first means of disconnect" at the meter. From the placard, underground wiring carries power to the house, which has a typical entrance panel with a typical main breaker... and to the barn, which has a typical entrance panel with a typical main breaker. Both panels have ground rods. Both panels have ground bus bars. Both panels have neutral bus bars. Both panels have a ground to neutral connection.

That's how mine is wired, too. I couldn't find the four wire direct burial cable and the electrical supply guy told me this (3-wire) was what I needed. It's not intrinsically dangerous to do it that way though it isn't NEC approved which I didn't know at the time. Except for the junction in the disconnect the neutral does go back directly to the service neutral ground. If I ever have to replace it, I will likely go with 4 wire from the disconnect but it is what it is and I am not afraid of it. From what I am hearing grounding a subpanel with a ground rod or buried wire does little to increase safety if the neutral (primary ground) fails as they are high resistance grounds that likely wouldn't even trip a breaker if a hot wire shorted to it.

 

[John T]

That's how mine is wired, too. I couldn't find the four wire direct burial cable and the electrical supply guy told me this (3-wire) was what I needed. It's not intrinsically dangerous to do it that way though it isn't NEC approved which I didn't know at the time. Except for the junction in the disconnect the neutral does go back directly to the service neutral ground. If I ever have to replace it, I will likely go with 4 wire from the disconnect but it is what it is and I am not afraid of it. From what I am hearing grounding a subpanel with a ground rod or buried wire does little to increase safety if the neutral (primary ground) fails as they are high resistance grounds that likely wouldn't even trip a breaker if a hot wire shorted to it.

I wouldn’t suggest any changes either and only unless and until local authority or insurance required it. I can only help people understand why nec made changes and it’s to reduce a risk or save a life or fire. The reason for only having a single n g bond is for life safety (I can’t explain it here sorry)?but hey that’s not how it used to be so keep on keepin on I say lol

John T

 

[zuhnc]

I also have the "first disconnect means" immediately below the meter. However, there are only THREE wires from those breakers to the panel in the house - two hots and a neutral, although the neutral is connected to a ground rod at the meter base. This means that my panels ARE where the bond between neutral and ground is located. The neutral to ground rod connection is not considered a bond point. That is done in the panels. There is also a ground wire from the neutral and ground busses in that panel to a ground rod.

Any panel I install that is fed from that panel MUST have four wires to it - hot, hot, neutral and equipment ground. And the sub-panel is NOT to have a N/G bond. But, I can have as many ground rods as I want at any of those sub-panels, connected to ONLY the ground buss, and never to the neutral buss.

If you have FOUR wires from your "first disconnect means" into any panel (H, H, N, G) then this (probably) means that your N/G bond is at the place of the first disconnect and NOT in your panel. Those panels connected this way are sub-panels, even though they are the main panel for the structure.

It is confusing, to be sure.

 

[farmersamm]

FYI Just to clear snd wrap up a few things above and some terminology I was taught by nec experts and board members and nec verbage when I practiced but beware nec may have since changed so don’t take my word consult the nec

A Grounding Electrode Conductor is the often no 4 bare copper wire from neutral to the grounding electrode system such as driven ground rods etc

An Equipment Grounding Conductor, (EGC) often just called ground by some, may be the bare or insulated green wire that may connect to non normal current carrying conductive appliance enclosures or junction boxes or panel tubs etc etc Back to the Equipment Gtound Buss in the panel

Purpose of the EGC is to carry only fault current providing a fault current return path so the breeker can trip and clear the fault

EGC might be smaller than current carrying conductors in certain cases all subject to nec as they only need to carry enough fault current for a certain time to allow the breaker to trip. Often and typical they are the same size as conductors you have to carefully consult the nec before going here lol

There is to be only one NG Bond typically at the first means if disconnect

Earthing or earth grounding the neutral is for hv surges spikes and lightning protection and providing a common low voltage reference for the grid

Note this is not exact or perfect it’s impossible to explain entire nec chapters here. It’s only my best recollection no warranty consult the nec not what’s posted here but I try my best to help best I can

John T

In this post you state "Purpose of the EGC is to carry only fault current providing a fault current return path so the breaker can trip and clear the fault"

If I say it, nobody listens............................... Here it is, straight from the horses mouth. Look carefully at the pics.

You have to bond ALL metal stuff in a building to provide a path from that metal to the ground rod.........in order for lighting induced voltage on those metal things to find a path to where it wants to go..........EARTH . This applies to enclosures, and the metal structure of the building(it it's a metal building).

Induced voltage wants to go to EARTH. GROUND FAULTS want to go to the UTILITY. The EGC serves a dual purpose..........it carries induced voltage, and ground fault voltage. A GEC carries voltage from the final bonded point to the ground rod................it carries lightning induced voltage brought to it by the GEC.

A ground rod should NEVER figure into a conversation about getting shocked by touching a live enclosure (this applies to other comments in preceding posts)

PARALLEL CIRCUITS............... You are, and always will be, a parallel circuit to the utility UNTIL the fault is cleared. Ground rods don't have a thing to do with it.........they don't protect you. Only the breaker makes the enclosure safe to touch, AND ONLY AFTER THE FAULT IS CLEARED. I would venture to say, that if you're leaning on an enclosure at the exact instant a hot wire contacts that enclosure..........you're probably toast. For the time it takes to trip the breaker..........you's part of the circuit.

Standard breakers protect EQUIPMENT, and to a very very limited degree people. If a circuit gets hot, the breaker flips........protecting wires, etc. If a hot contacts an enclosure, the breaker flips. If you touch a live wire, the breaker will not flip. This leads to a conversation about GFCI's.

IMHO.

 

[bc]

This is also why, in my little corner of the world, where I have often lived in old places with old wiring... when I install a ground. It's always at least as big as the hot and neutral. If somebody pulled a stunt that, like you say, puts ground in parallel with neutral... I want as much copper in parallel with me to ground as possible... enough to trip every breaker to the pole..lol.

It's always nice to know if your power company is using a delta, wye, or whatever configuration.

 

[will-max dairy]

That's how mine is wired, too. I couldn't find the four wire direct burial cable and the electrical supply guy told me this (3-wire) was what I needed. It's not intrinsically dangerous to do it that way though it isn't NEC approved which I didn't know at the time. Except for the junction in the disconnect the neutral does go back directly to the service neutral ground. If I ever have to replace it, I will likely go with 4 wire from the disconnect but it is what it is and I am not afraid of it. From what I am hearing grounding a subpanel with a ground rod or buried wire does little to increase safety if the neutral (primary ground) fails as they are high resistance grounds that likely wouldn't even trip a breaker if a hot wire shorted to it.

Yes. In the situation like yours, and mine. If the main panel connects to the sub panel with only a three wire cable; then the neutral in that three wire cable becomes critical. It is the only path for fault current back to the main panel.

The proper, four wire system, the fourth wire, if bonded to the neutral at the main, would provide a redundant, independent, path back to the main panel for fault current. It becomes a second layer of protection for the subpanels.

So, like you, I am not "afraid" of my house and barn wiring. But I respect that it's working with a single point of failure.

I also respect that, to change it without knowing what you're doing, could make it worse.

 

[John T]

In this post you state "Purpose of the EGC is to carry only fault current providing a fault current return path so the breaker can trip and clear the fault"

View attachment 101492
View attachment 101494

If I say it, nobody listens............................... Here it is, straight from the horses mouth. Look carefully at the pics.

You have to bond ALL metal stuff in a building to provide a path from that metal to the ground rod.........in order for lighting induced voltage on those metal things to find a path to where it wants to go..........EARTH . This applies to enclosures, and the metal structure of the building(it it's a metal building).

Induced voltage wants to go to EARTH. GROUND FAULTS want to go to the UTILITY. The EGC serves a dual purpose..........it carries induced voltage, and ground fault voltage. A GEC carries voltage from the final bonded point to the ground rod................it carries lightning induced voltage brought to it by the GEC.

A ground rod should NEVER figure into a conversation about getting shocked by touching a live enclosure (this applies to other comments in preceding posts)

PARALLEL CIRCUITS............... You are, and always will be, a parallel circuit to the utility UNTIL the fault is cleared. Ground rods don't have a thing to do with it.........they don't protect you. Only the breaker makes the enclosure safe to touch, AND ONLY AFTER THE FAULT IS CLEARED. I would venture to say, that if you're leaning on an enclosure at the exact instant a hot wire contacts that enclosure..........you're probably toast. For the time it takes to trip the breaker..........you's part of the circuit.

Standard breakers protect EQUIPMENT, and to a very very limited degree people. If a circuit gets hot, the breaker flips........protecting wires, etc. If a hot contacts an enclosure, the breaker flips. If you touch a live wire, the breaker will not flip. This leads to a conversation about GFCI's.

IMHO.

good job you’re sure hanging in there and gaining a good grasp on this I congratulate you !!! The thing is a person who is not a professional electrician or engineer or not studied and practiced the nec isn’t expected to get all this and that’s to be expected and nothing to be ashamed of. It took me time snd study to grasp it.

If nothing else if a lay person understands neutral is for normal return current while the EGC is there to carry fault current and the reason why there’s only one ng bond he has a good start

Thanks got taking the time to research snd post good info you may well help some you go to the head of the class. !!!

Best wishes God bless you and yours

John T. BSEE JD Retired but still interested in helping people with electricity !!!

 

[John T]

Definitely...first do no harm.

I'm not changing this. There are only three wires from the placard to the barn and three wires from the placard to the house... meaning... neutral and two phases.... I'm not floating any neutrals in the house or barn from their respective protective earth conductors (green wires in the building wiring) without the fourth wire from the placard.

Nor would I suggest you change it.
JT

 

[will-max dairy]

From above:

Quote:

PARALLEL CIRCUITS............... You are, and always will be, a parallel circuit to the utility UNTIL the fault is cleared. Only the breaker makes the enclosure safe to touch, AND ONLY AFTER THE FAULT IS CLEARED. I would venture to say, that if you're leaning on an enclosure at the exact instant a hot wire contacts that enclosure..........you're probably toast. For the time it takes to trip the breaker..........you's part of the circuit.

Unquote:

If the protective earth conductor back to the panel is of equivalent gauge to the hot; even while the fault is clearing, you will never be exposed to more than 1/2 of the utility voltage. The breaker trips the fastest (of these three cases)

If you touch an enclosure with a short fed by a #4AWG wire, with a #10AWG green wire back to the panel wire, you'll be exposed to about 4/5 of the utility voltage while the fault is clearing. The breaker trips, but more slowly than the first case

If there is no green wire at all, you'll be exposed to all of the utility voltage. The breaker doesn't even break a sweat; as it only takes about 60mA of current (at 60Hz) to kill a human being.

We often don't like to hear it, but size matters.


I agree with everything else said in the post that I pulled the quote from (#86 on this thread).

 

[John T]

My immediate reply to you was a bit off, and didn't address what you actually said.

Yeah..............it makes sense to have the equipment ground at about the same size as the hot wire. But.........what I'm wondering is........how much current does it take to flip the breaker. If a 10ga wire will carry the required current, I guess it's properly sized.

In the link I put up, the 10ga will handle a 60amp breaker. Sounds a bit small, but the NEC says it will(shrug)

You would have to look at the nec plus breaker specs to see how much and for how long it takes current to trip any certain breaker. Typically EGC is same size as conductors but for sure the nec can allow smaller

JT

 

[will-max dairy]

You would have to look at the nec plus breaker specs to see how much and for how long it takes current to trip any certain breaker. Typically EGC is same size as conductors but for sure the nec can allow smaller

JT

Sure. Codes are about due diligence. Nothing is 100% safe.

 

[John T]

I also have the "first disconnect means" immediately below the meter. However, there are only THREE wires from those breakers to the panel in the house - two hots and a neutral, although the neutral is connected to a ground rod at the meter base. This means that my panels ARE where the bond between neutral and ground is located. The neutral to ground rod connection is not considered a bond point. That is done in the panels. There is also a ground wire from the neutral and ground busses in that panel to a ground rod.

Any panel I install that is fed from that panel MUST have four wires to it - hot, hot, neutral and equipment ground. And the sub-panel is NOT to have a N/G bond. But, I can have as many ground rods as I want at any of those sub-panels, connected to ONLY the ground buss, and never to the neutral buss.

If you have FOUR wires from your "first disconnect means" into any panel (H, H, N, G) then this (probably) means that your N/G bond is at the place of the first disconnect and NOT in your panel. Those panels connected this way are sub-panels, even though they are the main panel for the structure.

It is confusing, to be sure.

X2 and Ditto it is confusing it was only after nec seminars study snd experience I understood it fully and the safety reasons for single ng bonds and 4 wires snd why sub panels have separate insulated and isolated n and g buses. But once you do it all makes sense yayyyy

John T

 

[John T]

I enjoyed and was pleasantly surprised at the interest and good questions above. Hey n g and ng bonding is confusing even to some professionals let alone non electricians or engineers it took me study practice and nec seminars to grasp it and I enjoy helping but again it can’t be explained to non sparkies here in a paragraph lol

Thanks to all who took part we pretty well beat the old n g bonding, reasons for a single ng bond and the difference in grounding g versus bonding horse to death lol

Thanks to those who took tine to look up and post info and for all the good questions people posted !!!

God bless yall

John T

 

[Janicholson]

From above:

Quote:

PARALLEL CIRCUITS............... You are, and always will be, a parallel circuit to the utility UNTIL the fault is cleared. Ground rods don't have a thing to do with it.........they don't protect you. Only the breaker makes the enclosure safe to touch, AND ONLY AFTER THE FAULT IS CLEARED. I would venture to say, that if you're leaning on an enclosure at the exact instant a hot wire contacts that enclosure..........you're probably toast. For the time it takes to trip the breaker..........you's part of the circuit.

Unquote:

If the protective earth conductor back to the panel is of equivalent gauge to the hot; even while the fault is clearing, you will never be exposed to more than 1/2 of the utility voltage.

If you touch an enclosure with a short fed by a #4AWG wire, with a #10AWG green wire back to the panel wire, you'll be exposed to about 4/5 of the utility voltage while the fault is clearing.

If there is no green wire at all, you'll be exposed to all of the utility voltage.

We often don't like to hear it, but size matters.


I agree with everything else said in the post that I pulled the quote from (#86 on this thread).

Not all, and I believe not many, ground faults are dead short from a L1 or L2 equipment connection to equipment ground.
I also believe the equipment is not intended to be protected by the breaker, only the wiring to the most local disconnect. Jim

 

[John T]

It's always nice to know if your power company is using a delta, wye, or whatever configuration.

If the service is transformers in a pole it’s easy to just look and see what service

John T

 

[John T]

Not all, and I believe not many, ground faults are dead short from a L1 or L2 equipment connection to equipment ground.
I also believe the equipment is not intended to be protected by the breaker, only the wiring to the most local disconnect. Jim

X2 and Ditto Professor. The overcurrent protection device, fuse or circuit breaker, is to protect the conductors from excess current and overheating while certain electrical components might have built in thermal overload protection. True many faults are from a hot line conductor short to case/frame or hot to Neutral

JT

 

[knightstead]

Amen ditto and x2 professor. If I recall the actual verbage is it the first means of disconnect which is typically the main panel

John T

Correct, first means of disconnect after a separately derived system. That’s going from memory, I’d have to knock the dust off my code book to confirm.

 

[will-max dairy]

Not all, and I believe not many, ground faults are dead short from a L1 or L2 equipment connection to equipment ground.
I also believe the equipment is not intended to be protected by the breaker, only the wiring to the most local disconnect. J

Breakers determine wiring size. Yes.

Breakers do not necessarily protect equipment. Yes.

But... protective Earth conductors (green wires) in equipment are designed to activate some kind of current limit (either the breaker or an internal fuse) in the case of a hot to chassis short. This is not an NEC thing. This is a UL thing.

As to all of the flavors what what can be called a "Ground Fault"? I really don't care, as long as my wiring doesn't burn up my house and a short to a metal chassis doesn't put me in touch with utility voltage.