Author Topic: How is Neutral Wire Neutral in Mains Electricity?  (Read 17972 times)

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Online paulca

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Re: How is Neutral Wire Neutral in Mains Electricity?
« Reply #50 on: January 16, 2020, 08:40:42 pm »
So this is mine.  It needs modernised ... the dark green earthing cable is a give away to it's age.  Consumer unit looks like it was replaced maybe 10 years ago, but at some point the place needs at least a partial rewire.

Oddly, the earth comes out of the tail block and into the side the main cable.  Wah?



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Offline Gyro

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Re: How is Neutral Wire Neutral in Mains Electricity?
« Reply #51 on: January 16, 2020, 08:45:25 pm »
A 3-core cable is not the type of cable used to service a single dwelling..

You might have a point, I did think it was straight that these were poking up at the kerbs, not at the house where the foundations where already in.  So maybe it's a 3 phase distribution cable and they connect single phases to houses later.

Likely - they'll tap off the armour (the CNE) and one phase to each properly, and drive an earth rod at some or possibly all of these joints. The cable to the building will almost certainly have been a straight concentric.

Yes they do. We lose a phase (usually ours) at least once a year where I live (badly installed paper insulated cable, I thing they bent it too much while burying). Three phase cores plus outer sheath neutral. Houses take taps between one phase and the Neutral sheath. I've watched them splicing in holes several times.

At least in the UK, most homes are TN-C-S. No earth spike, just Protective Earth bonded to Neutral at the entry and equipotential bonding to and between all pipework.

Best Regards, Chris
 

Offline Monkeh

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Re: How is Neutral Wire Neutral in Mains Electricity?
« Reply #52 on: January 16, 2020, 08:47:53 pm »
So this is mine.  It needs modernised ... the dark green earthing cable is a give away to it's age.  Consumer unit looks like it was replaced maybe 10 years ago, but at some point the place needs at least a partial rewire.

Oddly, the earth comes out of the tail block and into the side the main cable.  Wah?

That's a lead-sheathed cable (notice the wrapping, and the pitch marks on the board behind it) where the sheath has been connected to the neutral conductor. This likely means you've had major works on the distribution outside and been converted to a PME system. The lead will be acting as a nice earth rod for you - bonus.

The little white functional earth cable is odd. I don't think that RCD would use it, maybe there was a VOELCB there in the past.

All looks overdue an update, random loose breakers laying around is never a happy sign. Seals look to be missing (probably chopped when that RCD was fitted to replace whatever was there before).

If the cutout ever gets warm or starts leaking pitch (because it's warm..) call your DNO immediately. Those old cables are not the most reliable at terminations. Do not be tempted to wiggle anything or tighten the clamp.
« Last Edit: January 16, 2020, 08:49:35 pm by Monkeh »
 

Online paulca

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Re: How is Neutral Wire Neutral in Mains Electricity?
« Reply #53 on: January 16, 2020, 08:56:49 pm »
I checked it recently with a thermal camera and the only thing that looked even slightly warm was the mechanical meter itself.  However I didn't put much load on the system when I checked it.

The RCD looks like it was installed when the electric shower was fitted.  Not in the photo, but the tails are split, one set to the consumer unit and another to a single beaker+RCD for the 40A electric shower circuit.  Anyway I seen it on a few spark videos on YouTube, it seems it's common polite practice now, that if you need to break the seals (or get the correct authorised company to do it!) you install an RCD or isolator so the next spark along can isolate the consumer unit easily to work on it.

Now (or when I can afford/justify it) would be a good time to update/rewire as the shower circuit can come out as I converted the place to natural gas combi this year.  So I don't need that 40A circuit anymore and would prefer they split the upstairs downstairs plug rings instead maybe.

I think the little white earth wire is the earth sense for the RCD.  It was it that popped when I cut the cable.

Not related to electric, but my main issue with this meter cupboard under the stairs is the holes and gaps in the boards go straight into the dead space under the house and as it was once a coal fired house it has half a dozen air brick vents.  Literally, it's like 7*C in there right now and if I open a window in the house when it's windy the door gets blown open by the air rushing in through the floor!  Costing a fortune to heat and on my list to seal it with thermal underlay panels.
« Last Edit: January 16, 2020, 09:01:52 pm by paulca »
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Offline Monkeh

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Re: How is Neutral Wire Neutral in Mains Electricity?
« Reply #54 on: January 16, 2020, 09:01:07 pm »
All seems very wrong. The RCD should not require an earth at all, and it's not appropriate for protecting a shower anyway..
 

Offline floobydust

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Re: How is Neutral Wire Neutral in Mains Electricity?
« Reply #55 on: January 16, 2020, 09:08:05 pm »
In Canada and the USA, the distribution transformer center-tap is neutral and earth-grounded. So we have two: Line 1, Line 2. One more wire than 220VAC-only systems.
UK electrical seems quite different from North America. But the same result - Neutral and PE are bonded together. Just done in different locations, and in multiple places.

"consumer's union" we call "main breaker panel, or service panel".
"supply authority" we call "utility company"

We don't allow combustibles i.e. fiber-board wood back panel  :o or a fiberglass enclosure, which I see in UK where the utility meter is located.






 

Offline GeorgeOfTheJungle

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Re: How is Neutral Wire Neutral in Mains Electricity?
« Reply #56 on: January 16, 2020, 09:11:36 pm »
I think the little white earth wire is the earth sense for the RCD.

Is that a voltage-operated RCD? If it has more than 4 wires coming in/out it surely is. That's obsolete tech. And does it say 100 mA? That's a lot! Normal ones trip at 30 mA.

All seems very wrong. The RCD should not require an earth at all

Exactly!
« Last Edit: January 16, 2020, 09:27:48 pm by GeorgeOfTheJungle »
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Offline Monkeh

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Re: How is Neutral Wire Neutral in Mains Electricity?
« Reply #57 on: January 16, 2020, 09:13:50 pm »
We don't allow combustibles i.e. fiber-board wood back panel  :o or a fiberglass enclosure, which I see in UK where the utility meter is located.

The wooden backboards are treated and require an immense amount of energy to combust (note: paulca's installation is not on such a treated board which makes me more suspicious). Frankly no worse than a metal box mounted on an otherwise wooden structure - you dump enough energy in, eventually it's going to burn. But we tend to have masonry construction, so even if a fire gets started in a meter cabinet it's not likely to do much. The cavity insulation might eventually burn depending on type..

There's been a huge move recently to metal clad enclosures for everything (.. on the consumer side..) due to a spate of fires. All of which were due to poorly trained (or untrained) monkeys who can't tighten terminals, who were going around replacing CUs under the false pretense that a change in regulations required everyone to switch to dual RCD boards. These same twats are now changing everyone to metal clad boards (same false pretense), which are still going to catch fire because they still don't tighten terminals, and nothing is actually better..
« Last Edit: January 16, 2020, 09:17:41 pm by Monkeh »
 

Offline stefan_trekkie

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Re: How is Neutral Wire Neutral in Mains Electricity?
« Reply #58 on: January 16, 2020, 09:30:12 pm »
You can get some low voltage on some point in the natural wire because the wire itself have some resistance and therefor - voltage drop. On heavy home load and poor grounding may have to 4-5 volts.
The natural wire is not power caring. It is the wire that is bridge between phases. You have three phase from your local power transformer and one phase is in one house (or one apartment) and the other is in the second house(apartment) and they 'must' have balance with equal loads on every phase. If you have equal loads in tree phase power cable the natural wire have ZERO current .. But in imperfect world you have always slight disbalance
 

Offline floobydust

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Re: How is Neutral Wire Neutral in Mains Electricity?
« Reply #59 on: January 16, 2020, 09:53:13 pm »
We don't allow combustibles i.e. fiber-board wood back panel  :o or a fiberglass enclosure, which I see in UK where the utility meter is located.

The wooden backboards are treated and require an immense amount of energy to combust (note: paulca's installation is not on such a treated board which makes me more suspicious). Frankly no worse than a metal box mounted on an otherwise wooden structure - you dump enough energy in, eventually it's going to burn. But we tend to have masonry construction, so even if a fire gets started in a meter cabinet it's not likely to do much. The cavity insulation might eventually burn depending on type..

There's been a huge move recently to metal clad enclosures for everything (.. on the consumer side..) due to a spate of fires. All of which were due to poorly trained (or untrained) monkeys who can't tighten terminals, who were going around replacing CUs under the false pretense that a change in regulations required everyone to switch to dual RCD boards. These same twats are now changing everyone to metal clad boards (same false pretense), which are still going to catch fire because they still don't tighten terminals, and nothing is actually better..

TBH in North America we require a metal enclosure for the "service entrance" and main breaker panel.
However, the service entrance, all that's in it is a socket and energy smart meter, and no fuse which I see as a requirement in the UK  :-+

There have been countless house fires with improperly designed and tested (to Overvoltage Category IV+) energy smart meter arcs and then you have an unlimited arc happening on the side of a house. Firefighters won't pour water on it. The only fuse is on the distribution transformer primary which doesn't pop because it's sized for 20+ houses. Videos show a wood home go down, many class action suits and recalls of smart meters until the safety standards caught up.
Point is, the utility meter metal box does nothing for fire protection, really.
 

Offline Monkeh

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Re: How is Neutral Wire Neutral in Mains Electricity?
« Reply #60 on: January 16, 2020, 09:58:08 pm »
I haven't really seen any cases of our smart meters failing due to design so far, only improper installation (quick, spring up an industry and put people through a week of training, then let them go mess with 100A terminals, nothing can go wrong!).
 

Online paulca

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Re: How is Neutral Wire Neutral in Mains Electricity?
« Reply #61 on: January 16, 2020, 10:12:22 pm »
On the functional Earth connection on the RCD (or RCBO maybe) I can only find this:
https://www.electriciansforums.net/threads/what-is-an-rcbos-functional-earth-connection-really-for.51405/

And yes, it does say, worryingly 80A, 240V, 100mA.  If 100mA is it's fault current limit it's obviously not going to save a person!  I thought these days they were around 6mA and they are only that high because of switch mode power supplies causing nuance trips all the time.

I could probably test that fairly easily, but it would involve putting resistors across Live and Earth which would need to be done extremely carefully.

Out of interest the other Breaker + RCD (not in the photo) for the shower.  Why would this not be appropriate protection for an electric shower?
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Offline Monkeh

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Re: How is Neutral Wire Neutral in Mains Electricity?
« Reply #62 on: January 16, 2020, 10:40:55 pm »
Out of interest the other Breaker + RCD (not in the photo) for the shower.  Why would this not be appropriate protection for an electric shower?

Because it's 100mA.
 

Offline Renate

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Re: How is Neutral Wire Neutral in Mains Electricity?
« Reply #63 on: January 17, 2020, 11:33:19 am »
My, oh, my, what a can of worms we have here.
To address the question in the OP:

Neutral is a current carrying wire, therefore it will sometimes have a voltage drop across it.
In US-centric terms: 50 feet (one way) 14AWG copper wire will have 1.7V drop on it when you run your 15 ampere toaster on it.
That's an RMS voltage, so the peak is 2.4V, the peak-to-peak 4.8V

The idea of the ground wire (protective earth) is that it should never normally carry any current over it.
Therefore it should not have this couple of volts on it that the neutral does.

How the ground gets connected and where is a separate issue.
In systems where there is lots of metal cases and conduits all hooked together and running in circles
even this ground can get polluted from cross connection to building ground, water pipes, gas pipes, whatever.
That's why we have "IG" insulated ground where an insulated wire runs between a grounding rod all the way to a special orange outlet.
This kind of thing is used in hospitals and electronic facilities where interference is an issue.
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Online paulca

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Re: How is Neutral Wire Neutral in Mains Electricity?
« Reply #64 on: January 17, 2020, 12:08:27 pm »
Out of interest the other Breaker + RCD (not in the photo) for the shower.  Why would this not be appropriate protection for an electric shower?

Because it's 100mA.

Well, yes, as I said, the other RCD not in the photo.  However as it turns out it has an I delta N of 30mA.  So not life saving either.  However a quick google suggests that indeed the regs are for a 30mA RCD for a shower.  Maybe there is some expected leakage which would make a 3mA or 6mA RCD un-usable.


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Offline KeepItSimpleStupid

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Re: How is Neutral Wire Neutral in Mains Electricity?
« Reply #65 on: January 17, 2020, 05:53:02 pm »
My turn.

There is a REFERENCE (Earth/ground), a RETURN (neutral) and at least one live.
there is one point for a dwelling where the reference and the return are connected together.
The reference/ground is not supposed to carry current except during a fault.

Now we can also talk about bonding.  Your copper plumbing gets connected to earth/ground.  There is no current flow normally.

If you touch the washer and the water pipes, you don't get shocked.

Now you have to analyze faults.

A hot wire touches the grounded case of the washer.  Large current through the ground wire which is an alternate path to the neutral and the breaker trips.

insulation breakdown in the washer and a human touches the washer.  A little bit of current >7mA goes through the human.  The GFCI (RCD) breaker detects this by measuring the difference of currents between hot an neutral.  Human doesn't get harmed.

A poor connection an a lamp starts to arc, so the AFCI (Arc fault catches that).

Let's go back to this EARTH thing again.  During a lightning storm, the potential across the earth changes.
So, your garage might be at a different potential than the house and it might be from static electricity, so we put a ground  rod at the detached garage.

Now lets add the complication of a sidewalk surrounding a swimming pool.  Guess what, the  sidewalk is done differently than the sidewalk in front of your house.  You have to prevent a shock between the pool water and the sidewalk during a lightning storm.

Maybe this helps.  Maybe it doesn't.



PS: I'll add a comment about hopitals, transmitters and daisy chaining power outlets and isolated ground outlets if this is understood.





« Last Edit: January 17, 2020, 06:33:47 pm by KeepItSimpleStupid »
 

Offline IDEngineer

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Re: How is Neutral Wire Neutral in Mains Electricity?
« Reply #66 on: January 20, 2020, 06:22:59 pm »
I am kind of confused about the Live and Neutral wires in Mains wiring. I've seen YouTube videos where someone touches the Neutral wire, but it doesn't shock them, but touching the Live wire does.
Aw, what the heck, I'll wade in here too....

1) From Kirchhoff's current law, we know that the current into a mode must equal the current out of that node. If you have a load (light bulb, motor, heating element, whatever) between the "live" (black) and "neutral" (white) AC wires, both wires are carrying the same current. Yes, it's reversing 60 times per second (in the USA), but the current has to be the same. And if the current is reversing... which side is the "source"? The electron flow isn't "stronger" when the black wire happens to be positive, or vice versa. That white "neutral" wire is carrying current and can shock you. Does this change if it's connected to a copper grounding rod? Does the distance from said copper grounding rod matter? What is the inductance between the node in question and the copper rod connection? Are you CERTAIN there are no wiring errors in your house? We can argue about the finer details but are you willing to bet your life on it?

2) To understand where the concept of "neutral" originates, think of a center tapped transformer with its 240VAC output connected to your breaker panel's input. If you connect a 240VAC load (like an electric furnace, electric oven, electric dryer, etc.) then the reversing electron flow occurs between the two "live" wires (black and red) and the center tap (white) would see no current flow. Indeed, many such appliances don't even require a connection to the center tap (white) for precisely this reason. But what happens when you connect a 120VAC appliance? Now the circuit is closed by the center tap (white)... and that center tap is conducting current, as explained in #1 above.

3) All of the above is based on relative voltage potentials. For current to flow, there must be a voltage differential - and a voltage is always measured relative to some reference point. From one point of reference, the center tap (white wire) sits at zero VAC because it's the center tap of the power company's transformer and the 240VAC legs (black and red) oscillate around it. However, if you connect an AC voltmeter from black to white, or red to white, you'll still measure AC voltage. Go ahead, reverse the leads of the voltmeter - the AC voltage is still there! {grin} And if YOU are a current path between any two nodes of differing voltage, you can conduct current. The electrons don't care that you're a human. They don't care that there's another, perhaps lower reactance path in parallel with you. Some of those electrons will be happy to use you as their path to complete the circuit, and your body won't be happy that they do. We must respect electricity because electricity has zero respect for us.

Quote
I've seen YouTube videos where someone touches the Neutral wire, but it doesn't shock them, but touching the Live wire does.
YouTube is the modern-day equivalent of Darwin, always trying to clean up the gene pool!

Under certain circumstances, if you were fully and completely electrically isolated from everything else, you could touch even the black or red wire - by itself - and not get shocked. Technically your body would be raised to the same AC voltage potential but since you'd only be in contact with ONE point, there'd be no opportunity for current to flow. This is why birds can sit on power lines, Tesla has those photos of himself being raised to hundreds of kilovolts, etc. It's not solely about being at any given voltage potential... it's about current flow. Current is what kills you, voltage just makes the current possible.

Bottom line: It is NOT inherently safe to cavalierly touch the center tap. When I'm working on AC power, I presume ALL wires are potentially lethal. I kill the breaker in question and then I ALSO check using a handheld "power checker" (electric field detector) that I've tested on a known-live circuit moments before. And even then, I don't touch more than one wire at a time if I can help it. This is your life you're gambling with.
 

Offline IDEngineer

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Re: How is Neutral Wire Neutral in Mains Electricity?
« Reply #67 on: January 20, 2020, 06:36:46 pm »
So many triggers in a single message!

A poor connection an a lamp starts to arc, so the AFCI (Arc fault catches that).
AFCI's also "detect" welders and happily turn off to "protect" you from them. Grrrr. A recent remodel in my house required me (per NEC) to use all AFCI breakers. First time I connected my MIG welder, the freakin' 10X-as-expensive AFCI simply refused to let the welder operate. (It's an "arc" welder! It's literally how they work!) I ended up running a 12ga extension cord to another, distant outlet that wasn't part of the remodel. Of course, NEC also wants to minimize the use of extension cords (they regularly decrease the allowed distance between outlets for precisely that reason). So which is it? They literally want it both ways.

Quote
So, your garage might be at a different potential than the house and it might be from static electricity, so we put a ground  rod at the detached garage.
Yep, that's what I do! Except that NEC doesn't allow that anymore. A few years ago, I helped my brother wire up his brand new detached garage. Thinking like an Engineer (and not like an Electrical Inspector!), we drove in a 10 foot copper grounding rod to provide a separate, dedicated earth reference for the garage. The three wires of the 240VAC service (black, red, and white) came through conduit that we buried 18+ inches below grade, per NEC. We bonded the neutral to the earth reference at the garage breaker panel. Everything worked. But when the Inspector came for the final, he refused to sign off because NEC required that we run a ground wire between the buildings and not use the separate ground rod. The detached garage was only to have its earth reference from the other building. I tried to reason with the Inspector, pointing out that a separate ground rod - closer to the breaker panel in question - was actually BETTER and SAFER than running a separate copper wire nearly 100 extra feet to the breaker panel in the main house. How was the connection from the power company to the house - a three wire connection with its own copper ground rod - different from the garage, which treated the house like the power company and received a three wire connection with its own copper ground rod? The logic finally got him, and he devolved to (actual quote) "Unless you do it my way, I'm not signing it".

So we did it his way. We pulled a fourth, bare copper wire through the underground conduit. And after he left we reconnected the second ground rod. We left the connection between the two buildings too. More is better, right? Grrrr.
« Last Edit: January 20, 2020, 06:42:43 pm by IDEngineer »
 

Offline Monkeh

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Re: How is Neutral Wire Neutral in Mains Electricity?
« Reply #68 on: January 20, 2020, 06:44:02 pm »
Yep, that's what I do! Except that NEC doesn't allow that anymore. A few years ago, I helped my brother wire up his brand new detached garage. Thinking like an Engineer (and not like an Electrical Inspector!), we drove in a 10 foot copper grounding rod to provide a separate, dedicated earth reference for the garage. The three wires of the 240VAC service (black, red, and white) came through conduit that we buried 18+ inches below grade, per NEC. Everything worked. But when the Inspector came for the final, he refused to sign off because NEC required that we run a ground wire between the buildings and not use the separate ground rod. The detached garage was only to have its earth reference from the other building. I tried to reason with the Inspector, pointing out that a separate ground rod - closer to the breaker panel in question - was actually BETTER and SAFER than running a separate copper wire nearly 100 extra feet to the breaker panel in the main house. The logic finally got him, and he devolved to (actual quote) "Unless you do it my way, I'm not signing it".

Better and safer? Did you verify the loop impedance of your earth rod? No, then how do you know the breakers will operate correctly? What you did was completely change the earthing arrangement!
 

Offline IDEngineer

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Re: How is Neutral Wire Neutral in Mains Electricity?
« Reply #69 on: January 20, 2020, 09:31:45 pm »
Did you verify the loop impedance of your earth rod?
Do you think the Inspectors measure the loop impedance? Do you think the Inspectors even understand the concept of loop impedance? I can guarantee you this one didn't, and none of the others I've worked with over the years did either. Some of them have been very good and very well informed, but the heart of their knowledge is the code - not pure electrical theory.

Think about how power wiring works. In the original house, a three wire connection came into the panel (two phases and neutral). The earth reference came from a copper rod in the ground next to the house, which is bonded to neutral at the breaker panel.

What I did for his standalone garage was EXACTLY the same thing. We brought a three wire connection into the panel (two phases and neutral) and the earth reference came from a copper rod in the ground next to the garage, bonded to neutral at the breaker panel.

What the Inspector demanded was to abandon the (local) earth reference, and instead rely on a nearly 100 foot long run of copper wire back to the main house panel. When discussing circuitry on this forum, we often worry about a few centimeters of copper trace introducing excessive and unnecessary impedance into a ground reference carrying milli- or microamps. Here we're talking dozens of feet, potentially carrying tens of amps if a fault occurs. I'll take the closer, shorter, lower impedance earth reference.

how do you know the breakers will operate correctly?
Breaker operation is not affected by the earth reference. Even the most recent AFCI/GFCI breakers do not have a connection to earth - only to neutral. And while neutral is bonded to the earth reference at the panel, that is outside the circuit being monitored by the breaker.

EDIT: It might pay to review how breakers work.

GFCI's monitor the current flow on both sides of the circuit (live and return). Those should be equal under normal conditions. If the GFCI detects a differential current above some threshold, it opens the breaker because some of the current is following a path other than back through the breaker - and that path might be a human body.

AFCI's monitor (very roughly speaking) the rate of change of current flow. This allows them to detect arcs regardless of the absolute amount of current that is flowing.

The two types of detection are not interchangeable, which leads to three individual types of breakers: 1) Current-only (traditional), 2) GFCI's, and 3) AFCI's. There is a fourth style that is a combo AFCI/GFCI. Note that the three latter types incorporate the first, in that all of them will trip on excessive current. The point of the latter three types is that there are fault conditions that do not necessarily involve excessive current; you can kill someone without 15A of AC, and you can start a fire from an arc sustaining far less that 15A too.

None of the above involves nor requires an earth reference.
« Last Edit: January 20, 2020, 09:43:15 pm by IDEngineer »
 

Offline Monkeh

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Re: How is Neutral Wire Neutral in Mains Electricity?
« Reply #70 on: January 20, 2020, 09:38:33 pm »
Did you verify the loop impedance of your earth rod?
Do you think the Inspectors measure the loop impedance? Do you think the Inspectors even understand the concept of loop impedance? I can guarantee you this one didn't, and none of the others I've worked with over the years did either. Some of them have been very good and very well informed, but the heart of their knowledge is the code - not pure electrical theory.

I.. don't care if they do or not, they didn't install the system, and they're not the ones responsible for it..

Quote
Think about how power wiring works. In the original house, a three wire connection came into the panel (two phases and neutral). The earth reference came from a copper rod in the ground next to the house, which is bonded to neutral at the breaker panel.

What I did for his standalone garage was EXACTLY the same thing. We brought a three wire connection into the panel (two phases and neutral) and the earth reference came from a copper rod in the ground next to the garage, bonded to neutral at the breaker panel.

Ah, I see how the edit has changed the story.

You took it upon yourself to run a CNE to an outbuilding from an installation where it's already been split, and then split it again.. Now I don't know your regs, but things are done in specific ways for good reasons, and you thought you'd just figure it out for yourself.

Quote
Breaker operation is not affected by the earth reference. Even the most recent AFCI/GFCI breakers do not have a connection to earth - only to neutral. And while neutral is bonded to the earth reference at the panel, that is outside the circuit being monitored by the breaker.

If you have a fault to earth and your only earth connection to the source (as you were unclear in your post) is a rod.. yes, it's very much affected by how good that rod is.
« Last Edit: January 20, 2020, 09:40:29 pm by Monkeh »
 

Offline IDEngineer

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Re: How is Neutral Wire Neutral in Mains Electricity?
« Reply #71 on: January 20, 2020, 09:47:22 pm »
If you have a fault to earth and your only earth connection to the source (as you were unclear in your post) is a rod.. yes, it's very much affected by how good that rod is.

Why would a similar rod, at the other end of 100 feet of copper wire, be an improvement over a much closer rod at the end of a much shorter run of wire? That's what you're advocating. This is not an academic question, I sincerely want to know why introducing 100 feet of copper wire is safer or better.

As you prepare your response, remember that same "much closer rod at the end of a much shorter wire" was deemed good enough for the first building. If a neighbor built a new house next door, perhaps even closer than this garage, they'd do exactly the same thing as we did in the garage. Why does electricity behave differently just because it's on a different side of a human-created property line?
 

Offline IDEngineer

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Re: How is Neutral Wire Neutral in Mains Electricity?
« Reply #72 on: January 20, 2020, 09:54:11 pm »
If you have a fault to earth and your only earth connection to the source (as you were unclear in your post) is a rod.. yes, it's very much affected by how good that rod is.
Actually, not. Again, breakers do not work from an earth reference. See my added discussion of the three types of breakers above. For your example of a "fault to earth", you'll have either 1) excessive current (in which case the overcurrent aspect of all breakers will trip) or 2) imbalanced current, the exact situation a GFCI is meant to detect and defeat. And by the way, that's an excellent example of why GFCI's are a good idea (because a traditional breaker will not detect all such "fault to earth" conditions).

None of the breakers are affected by the system's earth reference. If you doubt that, ask yourself if the breakers would operate correctly if the fault occurred with a two-wire appliance, or one where the user had cut off the ground lug on its cord. The answer is yes, all breaker types would still correctly detect their fault conditions and operate properly.
 

Offline Monkeh

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Re: How is Neutral Wire Neutral in Mains Electricity?
« Reply #73 on: January 20, 2020, 09:59:06 pm »
If you have a fault to earth and your only earth connection to the source (as you were unclear in your post) is a rod.. yes, it's very much affected by how good that rod is.
For your example of a "fault to earth", you'll have either 1) excessive current (in which case the overcurrent aspect of all breakers will trip)

And if the impedance of your earth rod is too high for excessive current to flow...

Again, you initially did not mention connecting the neutral to your local rod - creating a TT system in which your earth is extremely poor.
 

Offline IDEngineer

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Re: How is Neutral Wire Neutral in Mains Electricity?
« Reply #74 on: January 20, 2020, 10:07:46 pm »
And if the impedance of your earth rod is too high for excessive current to flow...
...then 1) you're not getting the protection you expect from your earth ground system, which is its own separate problem; and 2) if an imbalanced current is flowing, then it's finding a separate path which is the exact situation a GFCI is intended to detect, so you are still being protected. Again, consider the case of a two-wire appliance with no earth reference at all.

Quote
Again, you initially did not mention connecting the neutral to your local rod
Neutral and earth are supposed to be bonded in the panel. That's what existed in the original structure. That's what a neighbor would do if they built ten feet away (five foot setbacks on either side of the property line). That's what we did for the garage, too, which was more than ten feet away.

I'm still waiting to hear how a more distant earth reference is somehow better and safer.
 


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