How is Neutral Wire Neutral in Mains Electricity? - Page 1
Forum section: electronics / beginners

author: help_me_pick_username
author_rank: Contributor
timestamp: January 14, 2020, 08:22:21 am
content: 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.I'm going to try and explain my understanding of how Mains AC electricity works, please let me know where I am wrong. My understanding is that, if I simplify the AC waveform to simply a square wave instead of Sinosodial, 60Hz AC is where one wire is +240v and the other is ground 30 times a second, and for the other 30 times, this is flipped, so the other wire is +240v, and the other is ground. I know this is wrong, since you wouldn't be able to touch Neutral in this case, but where am I wrong?

author: tszaboo
author_rank: Super Contributor
timestamp: January 14, 2020, 08:41:41 am
content: No. Phase has a sine wave on it. Like below. Sometimes positive, sometimes negative.Neutral is 0V, constantly, normally conducting electricity.Protetive earth is 0V as well, but it doesnt conduct normally electricity.Dont touch any of these wires with bare hands, even if people like Eleoctroboom do this, it is extremely foolish. Buy a electricians glove, it costs like 3 dollars, and switch off the circuit breaker if you work on the wires.

author: help_me_pick_username
author_rank: Contributor
timestamp: January 14, 2020, 08:54:50 am
content: It was never my intention to touch any of these wires, I was simply using that as an exmaple to explain my question.I don't really understand how negative voltage works. I will have to do some more research on this.When the Live wire is in it's negative state, doesn't that mean that Neutral is +240v relative to the Live wire? Sorry if these are stupid questions. I'm having some trouble wrapping my head around this.

author: magic
author_rank: Super Contributor
timestamp: January 14, 2020, 09:14:04 am
content: Absolute electric potential is determined by excess or deficit of electric charge. It can be positive or negative. Earth is neither positively nor negatively charged so its potential is zero. Neutral is connected to earth so its potential is zero. You are neutrally charged too so nothing happens when you touch neutral, unless the installation is broken or you actually are statically charged and get a spark.Live is alternately positive or negative. Neutral may be +240V relative to live when live is -240V, but it's still 0V relative to ground.Now, if you isolate your floor from ground, connect it to live, stand barefoot on the floor and touch neutral, that's going to hurt

author: tszaboo
author_rank: Super Contributor
timestamp: January 14, 2020, 09:42:14 am
content: Voltage is always relative. Meaning, that you always measure it between two points. It is that way by definition.You take one point as the reference point, for example protective earth, place the black electrode of the multimeter on it, and measure it against it. So yes, if you swap the mutimeter wires, the polarity of the voltage changes. We just use a reference point, because then everyone understands what voltage we talk about.

author: hsn93
author_rank: Regular Contributor
timestamp: January 14, 2020, 09:44:19 am
content: Quote from: help_me_pick_username on January 14, 2020, 08:54:50 amyes,, relative to the live..so u cant touch both togother..however, its still ~0v relative to earth

author: jeroen79
author_rank: Frequent Contributor
timestamp: January 14, 2020, 09:46:11 am
content: The distributiontransformer near your house will have one side of secondary winding connected to earth.This point is the neutral, the other ends of the windings are the different phases.In a single phase system the neutral will carry the same current as the phase so there will be a voltage across it.Therefore it will not be at earth potential at the outlet, although very close to it.The earth in your house can be provided from several points.

author: help_me_pick_username
author_rank: Contributor
timestamp: January 14, 2020, 10:54:26 am
content: I have attatched a diagram. If, instead of 9v batteries, these were 240v power sources that were being switched on and off to make 240v AC, if you touched the reference point in the centre (the neutral wire...?), you would get shocked, right? Since you are touching the high side of the second power supply?

author: sokoloff
author_rank: Super Contributor
timestamp: January 14, 2020, 11:24:22 am
content: To get a shock, current has to flow. For current to flow, there has to be a complete circuit. If you touch only the center point, you won't get a shock, because there's no complete circuit. In fact, you could touch any part of it,provided you don't have any other means for the circuit to be completed.Watching this might help ground your understanding a bit. (Sorry for the pun.)

author: Mechatrommer
author_rank: Super Contributor
timestamp: January 14, 2020, 11:48:52 am
content: Quote from: help_me_pick_username on January 14, 2020, 10:54:26 amno. your body potential (voltage) only instantly raised to the same level of center point without you noticing, or vice versa. this is called static, static is no electric flow, no flow no shock. you only get a shock when you touch either low or high point with your other hand. in this case, your body has 2 different potential between your hands, electric will flow through that and you will get a shock...back to neutral wire, if you closely study the above diagram, neutral is connected to earth. your feet also connected to earth, so when you touch neutral wire, your hand is earth, feet is earth, same potential = no flow. no flow, no shock. but when you touch live wire, your feet is earth, but your hand is not, different potential = different voltage... different voltage, electric will flow. there is flow, there is shock.. regardless of direction +ve or -ve.

author: help_me_pick_username
author_rank: Contributor
timestamp: January 14, 2020, 12:15:30 pm
content: Quote from: Mechatrommer on January 14, 2020, 11:48:52 amHow is the centre connection connected to earth in my diagram? If the two batteries are completely isolated, does that mean that the Neutral is thought of as connected to earth...?

author: sokoloff
author_rank: Super Contributor
timestamp: January 14, 2020, 12:38:42 pm
content: Quote from: help_me_pick_username on January 14, 2020, 12:15:30 pmI think he is talking about jeroene79's diagram, where neutral is literally connected to earth.Quote from: help_me_pick_username on January 14, 2020, 12:15:30 pmElectricity doesn't "think". In residential service, neutral is connected to earth at the service entrance. After that, neutral and groundshould not be considered to be the same.In the case of someone touching the center connection of your two batteries, also touching earth, and no other connections to complete the circuit,that personbecomes the (high resistance/impedance) connection between the center point and earth.

author: calzap
author_rank: Frequent Contributor
timestamp: January 14, 2020, 03:52:41 pm
content: Deliberately touching an energized neutral wire or terminal with bare skin (or bare metal tool) is a really bad idea. It might not actually be a neutral! Even if you test it with a meter first, don't touch it with bare skin. Someone flipping a switch or plugging something in out of your sight might cause the supposed neutral to become hot.If you are touching a true neutral connection and the end of that neutral is disconnected back at the breaker box ... guess what? ... you are now the neutral conductor ... shocking huh? A true neutral can kill you if you if you insert yourself in its electrical path. If you were to disconnect the neutral for energized equipment and then touch both the wire end and its connection point, you will get shocked ... maybe lethally.There are other ways a neutral can shock you ... don't touch 'em without proper precautions. Main precautions are knowing what you're doing and de-energizing circuits (and verifying they're dead).Mike in California

author: paulca
author_rank: Super Contributor
timestamp: January 14, 2020, 04:24:32 pm
content: Quote from: sokoloff on January 14, 2020, 11:24:22 amI tested this several times as a kid. I got mixed results. Touching the live wire in a light switch did not get me a shock. However touching the end of the element in an electric heater did get me a mild shock.The difference to me is that the switch wire was live, but not part of a running flowing circuit. The electric fire element however ever was ON. Now while my body did not complete a circuit to ground, although there might have been some leakage, I did become part of the circuit through which electricity was flowing. Electricity follows the path of least resistance is the theory, but I wonder how much current flows into dead-ends momentarily, like water in a stream flowing into coves and bays.Still it's more likely I leaked a few mA into the chair/carpet/floor and eventually to ground. It was a mild shock, just enough to make you retract your hand rapidly and mutter "ouch!".

author: Mechatrommer
author_rank: Super Contributor
timestamp: January 14, 2020, 04:45:46 pm
content: Quote from: paulca on January 14, 2020, 04:24:32 pmthere's your problem. chair/carpet add resistance to earth. you may float with the circuit node you are touching you may even add slight static to the carpet. and there is also difference (resistance) between touching with dry hand and wet hand. next time, try with wet bare feet directly to wet ground and wet hand to get maximum fun (WARNING: use only tip of one finger from one hand, the other hand in the pocket, dont ever touch electricity with your palm, even with one hand. violating this may result RIP)

author: CatalinaWOW
author_rank: Super Contributor
timestamp: January 16, 2020, 03:15:24 am
content: Shock is 99% right. But there are two requirements - to complete a circuit and to have a potential difference.While I completely agree with the cautions about implementing this in practice, in principal the neutral and ground are at the same potential. So there will generally be no shock from touching neutral while being connected to ground by standing on it or other means. While you might get away with this far more often than not, there can actually be a shock for many reasons. The shock can be quite severe so don't mess with it. Don't make a practice of touching these connections when power is applied. Use meters to verify that there is no potential even when you think that no power is applied.The line side has it's potential driven positive and negative relative to the neutral by the power source. Since the neutral is normally tied to ground that results in a potential between line and ground. In this case a shock will almost always result. But just as in the case of the neutral lines there are conditions that can reduce or eliminate the shock. But these are rare and often not robust, so no matter what your experience in getting a mild or no shock don't depend on that. Assume that the line is hot relative to ground when energized. If you must touch the hot line take appropriate steps to de-energize the circuit. And before you touch it use a meter to verify that you were successful.The OP's post with two nine volt batteries has confused him because he hasn't fully understood the physical connection that (almost always) occurs between ground and neutral, and possibly also doesn't realize there is a variable but real connection between a human standing on a floor and ground (or earth depending on the terminology used in your area).

author: tkamiya
author_rank: Super Contributor
timestamp: January 16, 2020, 03:24:37 am
content: Let's simplify this.A simple, single phase mains feed has two wires. Live wire, and neutral wire. Voltage exists as difference between those two wires. When there is a difference in voltage, when connected, current flows.At this stage, it does not matter which one swings up and down and which one does not. It's all relative. If you base your measurement on neutral wire, live wire swings. If you base your measurement on live wire, neutral swings.What makes difference is that at power pole and your main feed, neutral wire is connected to ground. Therefore, it is at ground potential. So, it is now simple to think, neutral wire does not swing up or down. It stays at the ground potential. This is why it is neutral. This is why you can grab the neutral wire (white wire in USA) and not be in danger of electrical shock.I am not going to go into 3 phase stuff. It is not necessary for this discussion. In USA, a regular socket has 3 poles but last one is ground. Just ground. Remaining two is neutral and live. If you measure those two lines ASSUMING neutral is at ground potential (which it is), live swings 120 * 1.4 volt 60 times a second. (peak of AC is higher than what people refer to as "Voltage".)Since YOU (your body) is coupled weakly to ground, if you touch live, you complete the circuit and feel the shock. If you touch neutral, since you and the wire are both at ground potential, you won't be shocked. If you actually put your feet on the actual ground and touch live wire, you might die, since you are strongly coupled to the ground. Now, if you stand on a perfect insulator and few feet off the ground or away from anything metallic, you can touch live and not feel a thing. This is because with absence of ground, there is no way for live wire to "swing".Now, the disclaimer.... above is all true assuming everything is done correctly and no fault exists. I have seen many times things are screwed up. Never assume any wires are safe to touch. I am a licensed electrician but I always measure few times before touching anything.

author: HobGoblyn
author_rank: Unknown
timestamp: January 16, 2020, 09:36:48 am
content: I always presumed in the UK, neutral and earth are the same thing. ( I’m a beginner and learning a lot, just want to check my assumption is correct)I presumed the only reason it was necessary to also have earth pins on our plugs was to make double sure there was always a direct route to ground?In theory the way UK ring mains work, the neutral should already provide this?Am I talking rubbish?I also thought that if you do have to mess around with live mains voltage, you should always do it with your right hand and never your left, the reason being, a shock through your right hand to ground, through your right foot is much less likely to stop your heart ?Thanks

author: Ranayna
author_rank: Super Contributor
timestamp: January 16, 2020, 10:08:08 am
content: For the longest time I had massive problems internalizing what is going on there with live and neutral. My thoughts were: The mains polarity changes 50 times per second, so both ends have to be dangerous (for half the time), right?What helped me to "get it" was the following thought: "The electricity changes from 'pushing' to 'sucking' 50 times per second. The live is what does the pushing and sucking, the neutral is pushed to/sucked from". That is an analogy that fits the concept of live and neutral better for me.Maybe the issue for me was that I grew up with the water analogies in my Kosmos kitI likely also did not help that german plugs are not polarized, making the distinction largely irrelevant for non electricians.

author: paulca
author_rank: Super Contributor
timestamp: January 16, 2020, 01:14:30 pm
content: Quote from: HobGoblyn on January 16, 2020, 09:36:48 amThe Earth is there to provide a low resistance and deliberate failure path for fault current. So if LIVE touches the metal case of a toaster, then having that metal connected to earth causes a massive amount of current to flow, which causes fuses/breakers to blow preventing the fault from continuing. It also has a tendency to try and keep the toaster case close to Earth potential and reduce risk of current flowing into you to ground when it has a lovely low resistance path to take.Earth and Neutral and separate, someone previously posted the different types of grounds, but I believe in the UK it is often taken from the metal conduit where the mains power enters the house. In some instances this is not available, is plastic or is not good enough a ground rod is installed. Neutral remains neutral all the way back to the substation where it joins up into the 3 phase 11kV lines. It is probably earth referenced there. However due to voltage drop over the potentially miles of cable there can be a few volts potential between neutral and local ground.An RCD will often trip if you short neutral to ground. It actually makes it next to impossible to cut a cable without tripping the RCD. Even if you turn off the master power breaker/switch the RCD will still pop when you cut the cable as you will short neutral and earth.Check your own house, measure the voltage between earth and neutral. It is unlikely to be exactly zero, but it might be close.

author: sokoloff
author_rank: Super Contributor
timestamp: January 16, 2020, 01:37:41 pm
content: Quote from: paulca on January 16, 2020, 01:14:30 pmIn US residential service, the neutral and ground are bonded at the first service disconnect on a property.In the UK are they really kept separate all the way back to the medium voltage transformer at the substation? That seems unlikely. There's good reason for bonding on the property and bonding to other metal in-ground systems and metal in-building piping.

author: paulca
author_rank: Super Contributor
timestamp: January 16, 2020, 03:49:02 pm
content: Quote from: sokoloff on January 16, 2020, 01:37:41 pmI believe there are different standards used depending on how long ago the installation was done.In the UK a set of streets will have an 11kV 3 phase substation usually taking a drop line off an over high cable. The actual single phase residential cabling is usually underground buried in an armored plastic insulated cable (I believe in a ring). "Usually" as I think it really depends on if the area was cabled while being built or was cabled afterwards and putting them underground was tricky, so there are flying mains cables off poles to the house in some areas. My house has a rather thick cable arriving from a pole, but I'm fairly sure it's the telephone line.The substations are usually hidden away in grey boxes in "dead areas" where there wasn't enough room to build a house, fenced off with warning signs, they hum and buzz.I think in my locale these join up at distribution/switching yards and combine into 65kV or 110kV distribution lines.

author: HobGoblyn
author_rank: Unknown
timestamp: January 16, 2020, 04:08:51 pm
content: Quote from: paulca on January 16, 2020, 03:49:02 pmWe had a rare power cut a few months ago. What was odd was my house had no power, my neighbours house had no power, then next few houses had power, then the next few didn't. Half the small row of shops didn't etc.It almost looked like a wizard had waved his wand at a selection of random houses and said "no power"I presume they use single phase to supply various houses, hence the houses without electricity were connected to one (faulty) phase, while the others were connected to one of the other two?

author: paulca
author_rank: Super Contributor
timestamp: January 16, 2020, 04:15:44 pm
content: I'm not sure, but I think the final end distribution cable is a mess of branches and complications as bits will be added on at later times. It's probably a mess in most residential areas that weren't all built at the same time. Chances are there are multiple substations in your area and one of them tripped.Taking out a single phase and leaving the other two in use, while plausible would create a imbalance in the phases and generate more current on the return neutral which in balanced 3 phase carries virtually no current. It would seem logical that if one phase trips they would trip all 3... <shrug> No idea. I'm sure the grey beards will be along soon to correct me.Apparently it's not 110kV either...https://wiki.openstreetmap.org/wiki/Power_networks/Great_Britain

author: Monkeh
author_rank: Super Contributor
timestamp: January 16, 2020, 04:23:09 pm
content: Losing one or two phases out of three on a street (or a few streets) isn't uncommon - generally modern installations handle it with no ill effect. It's happened here a few times - some of the underground joints have gone bad over the last decade or so.

author: IanB
author_rank: Super Contributor
timestamp: January 16, 2020, 04:56:22 pm
content: Quote from: help_me_pick_username on January 14, 2020, 08:54:50 amOn reading the replies above, I don't think anyone has given you a simple answer to your question.The simple answer is that the neutral wire is neutral because it has the same potential as the ground you are standing on. You wouldn't normally get a shock by touching it because there is no potential difference (voltage) between the wire and the ground beneath your feet.To clear up an apparent misunderstanding, this is nothing to do with AC or DC, positive or negative voltages or anything like that. Neutral is neutral because somewhere behind the scenes it is connected to the earth. If two points are connected together they cannot have any voltage between them. Simple as that.The battery example is misleading because batteries are normally floating and not referenced to the earth ground at all. The so called "0 volts" between two batteries is not in any way the same as "ground".

author: Siwastaja
author_rank: Super Contributor
timestamp: January 16, 2020, 05:13:00 pm
content: Words "neutral", "live", and "ground" are all extremely confusing for beginners, and even very "experienced" people don't understand what they are doing; having these stupid terms around causes countless deaths globally, all the time.Let's start with this: the officially correct terminology is: neutral, live, and PROTECTIVE EARTH. There is no "ground".Got rid of the "ground", but two misleading terms still there!"Live" gives you a "feeling" it might be dangerous, with respect to something else. So far, so good, but that danger applies to the both wires.So you should consider this: both "live" and "neutral" ARE LIVE!!! (Unless otherwisen PROVEN, case-by-case.)Many countries have non-polarized plugs, so a device uses two live wires, one is randomly "neutral". Even with polarized plugs, wiring mistakes are very common. So, both are live.Better terms would be "phase" and "zero", for example. We use these terms in Finnish language! Using these terms, you could reserve the word "live" for a different meaning: being potentially dangerous in respect other wiring.

author: IanB
author_rank: Super Contributor
timestamp: January 16, 2020, 05:51:17 pm
content: Let's learn how to give simple answers to simple questions.If you drive a big metal stake into the ground and then attach a wire to it, it follows you shouldn't get a shock from that wire if you stand on the ground and touch it.That is what makes a wire "neutral". By attaching the wire to the metal stake you have "neutralized" it.

author: james_s
author_rank: Super Contributor
timestamp: January 16, 2020, 06:03:07 pm
content: Quote from: sokoloff on January 16, 2020, 01:37:41 pmI had a look in the panel (or "consumer unit" as he called it) in my friend's house in England when I was there and neutral was bonded to earth in the panel just like it is in the US. The only difference aside from physical form factor was the single 240V to neutral vs the split 240V phase earthed center tap that we have in the US.Running neutral all the way back to the substation would be absurd.

author: tkamiya
author_rank: Super Contributor
timestamp: January 16, 2020, 06:42:17 pm
content: In US, neutral and ground are at the same potential. (same voltage, same treatment, etc, etc, etc) If you connect a lamp, for example between ground and live, it will work. But it is against the electrical code and potentially dangerous.In US, by code, neutral and ground is connected together right after the power company meter. (typically where the main circuit breaker is) After that, they exist as separate wires. It is actually against the law to connect them together anywhere else. (This is to avoid what is called ground loop)The way it works is, neutral wire is there to carry the return current where as ground is there for safety. In normal situations (meaning if there are no problems and no faults) ground wires curries NO current. Its only reason for existence is to provide safety of residents, should something go wrong. It is a safety ground.Let's say you are using a toaster. Let's say safety ground does not exist like old days. Let's say insulation on live wire fell off/broke and it is touching the outer casing. If you happen to touch the toaster, you become the return path and get shocked. Since there is a safety ground connected to the case, it will cause a short condition and trip the circuit breaker even before you touch it.

author: GeorgeOfTheJungle
author_rank: Super Contributor
timestamp: January 16, 2020, 06:44:38 pm
content: Quote from: james_s on January 16, 2020, 06:03:07 pmHow so? You want the power to flow to ground?

author: tkamiya
author_rank: Super Contributor
timestamp: January 16, 2020, 06:48:12 pm
content: By the way....There are neutral potential in 3 phase feed from substation to the transformer. Except the wire does not actually exist. It's virtual. At the transformer, 2 wire out of 3 from the high side gets fed into it, and get converted to 120/240 volts. There, one side is grounded. That becomes the neutral.If you look at the telephone poles, you can see wires are in layers at different height. Top ones are high voltage. Second ones are low voltage (after transformer somewhere). Right there, neutral already exists.

author: Monkeh
author_rank: Super Contributor
timestamp: January 16, 2020, 07:00:42 pm
content: Quote from: Siwastaja on January 16, 2020, 05:13:00 pmLine (1, 2, 3), neutral, CPC. Line and neutral are live. Terminology already well under control, at least for some of us..Quote from: tkamiya on January 16, 2020, 06:48:12 pmExcept at that point it's a CNE, not a neutral.This thread is going to get incredibly bogged down with differing terminology and global practices.

author: Monkeh
author_rank: Super Contributor
timestamp: January 16, 2020, 07:04:16 pm
content: Quote from: james_s on January 16, 2020, 06:03:07 pmWhich is absolutelywrongon a CU in the UK! If that is done here it is in the cutout, before the meter, and you shouldn't even be able to remove the cover.

author: tkamiya
author_rank: Super Contributor
timestamp: January 16, 2020, 07:09:34 pm
content: What's CNE?Yes, it's different in each country. I'm actually licensed in Japan and I live in US now. Differences are amazing. Yet, this is a global forum. This kind of confusion happens all the time.

author: Monkeh
author_rank: Super Contributor
timestamp: January 16, 2020, 07:13:25 pm
content: Quote from: tkamiya on January 16, 2020, 07:09:34 pmCombined Neutral Earth. ie. a live, current carrying conductor which is neither one nor the other. A neutral can only be neutral in reference to a 'ground' (CPC, in our terminology), which does not exist as a separate entity at this point.It's the return path of a specialised distribution which doesn't apply to installations. Once at the installation you'd split this out into the two separate conductors.

author: floobydust
author_rank: Super Contributor
timestamp: January 16, 2020, 07:20:56 pm
content: You guys are confusing the parts of mains power systems, I worked in the utility industry.At the electrical transmission level, it's all 3-wire 3-phase output with a local Wye ground only at the generating substation. It's OK to have no neutral, and the only ground wire is for lightning protection of the transmission lines. Typically 240kV to around 25kV.At the electrical distribution level, it's mostly 1-phase takeoff from the 3-phase transmission system with a neutral (local ground) at the substation. Neutral is daisy-chained throughout the distribution system in a residential area for example. Typically 25kV to 220VAC.At the house level, incoming neutral is bonded to earth-ground in the main panel.Electrical codes and safety standards require the secondary of a mains transformer (substation or pole pig) to be referenced to earth-ground.This is only because a primary-secondary fault would otherwise raise the system voltage to hazardous levels, example a 25kV-220VAC distribution transformer. You don't want 25kV common-mode on your house wiring which would start fires.Of course there are exceptions where neutral wire is actually run (transmission line) scenario, if earth impedance is super high, mountainous igneous rock for example. Lightning strikes need a place to go.

author: GeorgeOfTheJungle
author_rank: Super Contributor
timestamp: January 16, 2020, 07:41:42 pm
content: Quote from: floobydust on January 16, 2020, 07:20:56 pmNo, it isn't, not where I live. Protective earth is not connected to neutral, only to GND like this:

author: Monkeh
author_rank: Super Contributor
timestamp: January 16, 2020, 07:42:23 pm
content: Quote from: floobydust on January 16, 2020, 07:20:56 pmAnd we see again how terminology differs.We would consider this the separation of a CNE into N and CPC (or E). Bonding is a different practice to keep local factors (building metalwork, conductive pipework which contacts ground, etc) at the same potential as the CPC.There's little point calling it 'neutral' when it has nothing to be neutral to, and current to 'earth', 'ground', 'CPC', etc inevitably is conducted down it.Of course, you do have situations where both a neutral and earth are carried all the way back to the transformer. Quite uncommon in new installations these days.

author: paulca
author_rank: Super Contributor
timestamp: January 16, 2020, 07:56:34 pm
content: I took a look in my meter box and it's too much of a mess to figure out what is really going on, but it looks like the earth disappears into the presentation box (the bit the utility company own) with the 100A fuse and the thick armoured cable that disappears under the floor.If Earth and Neutral were connected there then the RCD would not trip if you short neutral to earth as there would be no potential, no current and nothing to trip the RCD, but I have tested and N+E shorts do trip it.As an aside I did notice the top of the utility block is covered in fluff, dust and saw dust, so I will hit that with the hoover next time it's out, that worries me.

author: floobydust
author_rank: Super Contributor
timestamp: January 16, 2020, 07:57:57 pm
content: Quote from: GeorgeOfTheJungle on January 16, 2020, 07:41:42 pmI'm saying that ground-rod gets connected to neutral inside the breaker panel, at least in North America. There is a "neutral bar" inside the electrical panel joining the two.edit: added a pic

author: paulca
author_rank: Super Contributor
timestamp: January 16, 2020, 08:00:58 pm
content: Quote from: Monkeh on January 16, 2020, 07:42:23 pmI did find reference, on a site about EMF which said originally installations carried neutral right back to the substation or grounded locally via a ground rod.However newer installations started using "multi-point grounding" by grounding the neutral at multiply points in the distribution network. They claimed this causes magnetic fields due to net current flowing in the loops formed.But... without digging deeper I was concerned the website was possibly bat shit about the evils of EMF on people.

author: Monkeh
author_rank: Super Contributor
timestamp: January 16, 2020, 08:03:08 pm
content: Quote from: paulca on January 16, 2020, 07:56:34 pmOf course there would. If you short N and CPC after the RCD, current in an active circuit can take two paths to return, which is what will cause an RCD to trip.If your CPC goes into the cutout (generally the right hand side at the top), you have a CNE incoming and it's split at that point. This makes it a TN-C-S system, which is almost invariably PME. If it runs down to connect to the cable sheath below, it's likely a TN-S system with separate conductors back.Oh, and that cable isn't really armoured.

author: paulca
author_rank: Super Contributor
timestamp: January 16, 2020, 08:08:35 pm
content: Quote from: Monkeh on January 16, 2020, 08:03:08 pmNo. I pulled the breaker for the downstairs lights and went a cut the garage light cable as I didn't need it anymore. It popped the house RCD. This was not an active circuit the live was disconnected. However the RCD was able to detect the short between the neutral and earth.I just stuck the meter into my plug socket.L->E 232VN->E 2VL->N 230VI'm fairly sure it is armored. When I worked on a building site NIE (Northern Ireland Electric) would install them quite early on and leave them sticking out of the ground with blue ribbons on them. They were heavy black outer a ring of steal braids and 3 heavy cores.If they weren't armored and you stuck a spade deep enough you could cut it and take the street out.Besides UK electrical code requires that ALL mains voltage cables put underground are armored.

author: Monkeh
author_rank: Super Contributor
timestamp: January 16, 2020, 08:17:42 pm
content: Quote from: paulca on January 16, 2020, 08:08:35 pmBut because your RCD is common with multiple circuits, and you did not interrupt the neutral conductor with the MCB, you still effectively connected neutral and CPC for all other circuits downstream of the RCD.Quote2V across such a low impedance (sub-ohm likely, certainly very, very low ohms) will source more than enough current to trip an RCD!QuoteA 3-core cable is not the type of cable used to service a single dwelling..Older installations will be something like PILC - impregnated paper for insulation, a lead cladding providing 'armour' (it's lead - it's soft as butter) and the earth connection. Newer will use a concentric cable - for single phase installations this will be one core, solid or stranded, for the line, and an insulated wrapping of copper conductors under the outer sheath for the CNE. No armour, but if you hit it with a proper digger you should blow a very big fuse before a hole appears in your bucket.QuoteThis would be BS7671. The distribution networkdoes not operate under these regulations at all. That which you think you know from house wiring does not apply before the meter.

author: GeorgeOfTheJungle
author_rank: Super Contributor
timestamp: January 16, 2020, 08:17:49 pm
content: Quote from: floobydust on January 16, 2020, 07:57:57 pmIs that split-phase 240V thingy what you have in Canada too?

author: Monkeh
author_rank: Super Contributor
timestamp: January 16, 2020, 08:24:01 pm
content: To steal some images from another site, this is a straight concentric cable supplying a TN-C-S supply to a dwelling:That's what will be feeding my house. This one looks like 25mm².And this is a TN-S supply with a split concentric, same idea, but half the outer conductors are insulated for the neutral:This looks to be 16mm².Notice the complete lack of armour.I have nothing immediately to hand to show a lead-clad cable - presumably because those things are sealed with pitch and not easily cleaned for your viewing pleasure..

author: paulca
author_rank: Super Contributor
timestamp: January 16, 2020, 08:27:17 pm
content: Quote from: Monkeh on January 16, 2020, 08:17:42 pmYou might have a point, I did think it was strange 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.

author: Monkeh
author_rank: Super Contributor
timestamp: January 16, 2020, 08:28:33 pm
content: Quote from: paulca on January 16, 2020, 08:27:17 pmLikely - 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.

author: paulca
author_rank: Super Contributor
timestamp: January 16, 2020, 08:40:42 pm
content: 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?

author: Gyro
author_rank: Super Contributor
timestamp: January 16, 2020, 08:45:25 pm
content: Quote from: Monkeh on January 16, 2020, 08:28:33 pmYes 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.

author: Monkeh
author_rank: Super Contributor
timestamp: January 16, 2020, 08:47:53 pm
content: Quote from: paulca on January 16, 2020, 08:40:42 pmThat'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.

author: paulca
author_rank: Super Contributor
timestamp: January 16, 2020, 08:56:49 pm
content: 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.

author: Monkeh
author_rank: Super Contributor
timestamp: January 16, 2020, 09:01:07 pm
content: All seems very wrong. The RCD should not require an earth at all, and it's not appropriate for protecting a shower anyway..

author: floobydust
author_rank: Super Contributor
timestamp: January 16, 2020, 09:08:05 pm
content: 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 panelor a fiberglass enclosure, which I see in UK where the utility meter is located.

author: GeorgeOfTheJungle
author_rank: Super Contributor
timestamp: January 16, 2020, 09:11:36 pm
content: Quote from: paulca on January 16, 2020, 08:56:49 pmIs 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.Quote from: Monkeh on January 16, 2020, 09:01:07 pmExactly!

author: Monkeh
author_rank: Super Contributor
timestamp: January 16, 2020, 09:13:50 pm
content: Quote from: floobydust on January 16, 2020, 09:08:05 pmThe 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..

author: stefan_trekkie
author_rank: Contributor
timestamp: January 16, 2020, 09:30:12 pm
content: 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

author: floobydust
author_rank: Super Contributor
timestamp: January 16, 2020, 09:53:13 pm
content: Quote from: Monkeh on January 16, 2020, 09:13:50 pmTBH 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, andno fusewhich I see as a requirement in the UKThere 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.

author: Monkeh
author_rank: Super Contributor
timestamp: January 16, 2020, 09:58:08 pm
content: 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!).

author: paulca
author_rank: Super Contributor
timestamp: January 16, 2020, 10:12:22 pm
content: 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?

author: Monkeh
author_rank: Super Contributor
timestamp: January 16, 2020, 10:40:55 pm
content: Quote from: paulca on January 16, 2020, 10:12:22 pmBecause it's 100mA.

author: Renate
author_rank: Super Contributor
timestamp: January 17, 2020, 11:33:19 am
content: 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 4.8VThe idea of the ground wire (protective earth) is that it should nevernormallycarry 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 circleseven 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.

author: paulca
author_rank: Super Contributor
timestamp: January 17, 2020, 12:08:27 pm
content: Quote from: Monkeh on January 16, 2020, 10:40:55 pmWell, 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.

author: KeepItSimpleStupid
author_rank: Regular Contributor
timestamp: January 17, 2020, 05:53:02 pm
content: 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.

author: IDEngineer
author_rank: Super Contributor
timestamp: January 20, 2020, 06:22:59 pm
content: Quote from: help_me_pick_username on January 14, 2020, 08:22:21 amAw, what the heck, I'll wade in here too....1) From Kirchhoff's current law, we know that the currentintoa mode must equal the currentoutof 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.QuoteYouTube 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.

author: IDEngineer
author_rank: Super Contributor
timestamp: January 20, 2020, 06:36:46 pm
content: So many triggers in a single message!Quote from: KeepItSimpleStupid on January 17, 2020, 05:53:02 pmAFCI'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.QuoteYep, 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.

author: Monkeh
author_rank: Super Contributor
timestamp: January 20, 2020, 06:44:02 pm
content: Quote from: IDEngineer on January 20, 2020, 06:36:46 pmBetter 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!

author: IDEngineer
author_rank: Super Contributor
timestamp: January 20, 2020, 09:31:45 pm
content: Quote from: Monkeh on January 20, 2020, 06:44:02 pmDo you think the Inspectors measure the loop impedance? Do you think the Inspectors evenunderstandthe 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.Quote from: Monkeh on January 20, 2020, 06:44:02 pmBreaker operation is not affected by the earth reference. Even the most recent AFCI/GFCI breakers do not have a connection toearth- only toneutral. 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.

author: Monkeh
author_rank: Super Contributor
timestamp: January 20, 2020, 09:38:33 pm
content: Quote from: IDEngineer on January 20, 2020, 09:31:45 pmI.. don't care if they do or not, they didn't install the system, and they're not the ones responsible for it..QuoteAh, 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.QuoteIf 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.

author: IDEngineer
author_rank: Super Contributor
timestamp: January 20, 2020, 09:47:22 pm
content: Quote from: Monkeh on January 20, 2020, 09:38:33 pmWhy 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?

author: IDEngineer
author_rank: Super Contributor
timestamp: January 20, 2020, 09:54:11 pm
content: Quote from: Monkeh on January 20, 2020, 09:38:33 pmActually, 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.

author: Monkeh
author_rank: Super Contributor
timestamp: January 20, 2020, 09:59:06 pm
content: Quote from: IDEngineer on January 20, 2020, 09:54:11 pmAnd 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.

author: IDEngineer
author_rank: Super Contributor
timestamp: January 20, 2020, 10:07:46 pm
content: Quote from: Monkeh on January 20, 2020, 09:59:06 pm...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.QuoteNeutral 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.

author: Monkeh
author_rank: Super Contributor
timestamp: January 20, 2020, 10:15:29 pm
content: Quote from: IDEngineer on January 20, 2020, 10:07:46 pmIn the first panel. And this discussion shows precisely why nobody else does it that way..

author: sokoloff
author_rank: Super Contributor
timestamp: January 21, 2020, 12:06:30 am
content: The inspector has a crystal-clear NEC reference on his side (assuming the AHJ has adopted NEC of 2008 or later, which seems likely) to require a four-wire feed. I have no issue with that.I do think it's ridiculous that he demanded you disconnect the additional ground rods for the outbuilding and I'd have done exactly as you did in that case-reconnect them as soon as you had the sign-off and heard his car door close.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: January 21, 2020, 07:16:31 am
content: OK. I'm the slow guy in the back of the class. Why does the fourth case kill you? It requires the place the person is standing on to have a better path back to the ground rod than any of the ground or neutral wiring, which is certainly a possibility, but not a sure thing, and maybe not even likely. Having a local ground rod in the right hand building may make it more likely, but might not.

author: GeorgeOfTheJungle
author_rank: Super Contributor
timestamp: January 21, 2020, 11:33:41 am
content: Quote from: CatalinaWOW on January 21, 2020, 07:16:31 amNo, I'm the slow one, I don't even understand those drawings.

author: Siwastaja
author_rank: Super Contributor
timestamp: January 21, 2020, 11:51:21 am
content: Quote from: Monkeh on January 16, 2020, 07:00:42 pmThanks,this is the key. As you confirm, lineand neutralare bothlive. It's sad that "live" is just one letter from "line", both written and pronounced. "live and neutral", a phrase which shouldn't exist at all, produces 503 000, "line and neutral" 1 210 000 results on Google, same order of magnitude.Similar discussions happen everywhere, on- and offline, and they are always total train wrecks.Statements like "neutral and earth are the same", as seen in this thread, as well, while technically correct to a limited degree, are extremely dangerous and easily misunderstood. This statement has a scope: N and PE are the same, inside a certain distribution box which connects them together, when the wiring is correct. But a large percentage of people reading these discussions are not electricians wiring up distribution boxes; instead, they might apply what they hear when wiring appliances.Logical thinking based on the definitions:Live = dangerous,PE = not dangerous (otherwise it wouldn't be exposed everywhere!),Neutral = Live (by definition),Substituting Live = dangerous:Neutral = dangerousSubstituting Neutral = PE, as suggested by many (including in this thread!)Dangerous = not dangerous - a logical mismatchHence,Claim "Neutral = PE" does not hold (as per the rating of dangerousness based on definition of being live or not, which exists for good reasons).This is unsurprising - if neutral and PE were the same thing, why bother having the two?

author: paulca
author_rank: Super Contributor
timestamp: January 22, 2020, 08:50:26 am
content: Quote from: IDEngineer on January 20, 2020, 09:31:45 pmA quick google (and my own meter box) suggests different.https://www.google.com/search?q=rcd+functional+earth

author: sokoloff
author_rank: Super Contributor
timestamp: January 22, 2020, 02:48:12 pm
content: If an AFCI/GFCI breaker is installed in a subpanel, where neutral and ground are not tied together, is the tail on the breaker connected to neutral or to earth? (It’s tied to the neutral bus bar, not to earth.)

author: paulca
author_rank: Super Contributor
timestamp: January 22, 2020, 02:53:20 pm
content: Quote from: sokoloff on January 22, 2020, 02:48:12 pmIf that was in response to me. Mine was in response to the premise that AFCI/GFCI/RCD/RCBO's never have Earth. This is not the case. On a small amount of research the UK regulation do not require a functional Earth reference, but many RCD/RCBOs DO have an Earth reference as it allows them to detect somethings in addition to leaked current. Apparently with a functional earth reference they can still detect leaked current when there is loss of neutral.

author: IDEngineer
author_rank: Super Contributor
timestamp: January 22, 2020, 07:17:57 pm
content: A few points of clarification:* RCD's can be breakers or outlets (there are a few other specialized devices out there too, but most people won't encounter them). In the US the term GFCI is much more common, but means the same thing: A device that detects and reacts to an imbalance in current.* RCBO's are RCD's that also include overcurrent protection. Thus GFCIoutletsare RCD's, but GCFIbreakersare RCBO's.* This thread has been discussing breakers, not outlets.* GFCI outlets (usually) have a separate connection for an earth reference because three-wire appliances expect an earth reference. GFCIbreakerstypically do not have a (fourth) connection for an earth reference, at least not in the US. The third connection on GFCI breakers is a (usually white) pigtail that is to be connected to neutral, without regard to whether neutral is bonded locally or distantly to an earth reference. A GCFI breaker is therefore designed to function properly with, or without, a bond between neutral and an earth reference.While digging around on this topic, I ran across this rather interesting tidbit on Eaton's website (they make a lot of electrical devices):Quote...which further reinforces the point that an earth reference is not required for a residual current device to detect an imbalance of current - and by extension, that how the earth reference is obtained will not prevent a GFCI breaker from operating properly.Hopefully that finally lays to rest the assertion that one type of earth reference is "better" for GFCI's.Meanwhile, I continue to wait for someone to explain why they feel a copper rod at the other end of 100 feet of wire is somehow a better earth reference than a copper rod within a few feet of the breaker panel. So far, nothing. Quoting the NEC is just hand-waving, since the NEC changes all the time and sometimes contradicts itself with its own changes. Whatelectrical reasonmakes 100 feet of intermediate wire a better earth reference?

author: IanB
author_rank: Super Contributor
timestamp: January 22, 2020, 07:30:16 pm
content: Quote from: IDEngineer on January 22, 2020, 07:17:57 pmFor the sake of discussion, let me ask questions.Suppose the remote building is connected with 100 feet of earth wire back to the main panel in the main building. Now suppose there is a difference in potential between the local terrain and the earth wire connected to the main building (e.g. a lightning strike hitting the ground next to the remote building and raising the local ground potential). This could cause a significant voltage difference between the copper earth wire and the building framework that could potentially cause damage. If the remote building had a local copper ground rod as well as the earth wire back to the main building, would that make things better or worse?

author: paulca
author_rank: Super Contributor
timestamp: January 23, 2020, 11:06:06 am
content: I found this interesting... I think the point that the ground charge between the building and outbuilding being different is covered. Doesn't necessarily need to be lightening, but static. The resistance through the potentially dry soil will be significantly higher than through a copper conductor to equalizer the charge differential between the buildings. As I understand it anyway.

author: IDEngineer
author_rank: Super Contributor
timestamp: January 23, 2020, 08:59:23 pm
content: Quote from: paulca on January 23, 2020, 11:06:06 amSlightly changing the subject... I had an amazing demonstration of static in the atmosphere a few years ago. Our whole family is ham radio operators and we had (at that time) a 1/4 wave multiband vertical antenna on the top of our house, with LMA-400 coax coming to a permanent N-female outlet on the wall in the family room. All equipment was unplugged because nobody was using it. I heard a "SNAP" sound which I didn't recognize. Happened again after 15-30 seconds. Kept repeating every once in a while, which allowed me to start tracking it down. I finally found that the N-female was arcing from its center conductor to the shield... the arc was VERY visible and quite loud when you were near. I presumed there was a buildup of static outside, mentioned that to the family, and shortly thereafter we got the first clap of thunder. A significant rain/thunderstorm followed.This was a great learning opportunity for my then perhaps 10YO son (who had his General at the time). We regularly discussed antenna theory, so many volts per meter, etc. but nothing makes it real like seeing how a metal rod in the air can pick up enough voltage potential to visibly arc across a connector!I was really glad no sensitive receivers were connected to that N-female.Sorry for the thread hijack but your comment brought back a vivid memory.

author: richard.cs
author_rank: Super Contributor
timestamp: January 24, 2020, 01:51:02 pm
content: Quote from: Monkeh on January 16, 2020, 08:24:01 pmI've just stepped outside and taken some for your viewing pleasure. Various copper and aluminium cored PILCs, all four core (L1 L2 L3 and N) with the lead used as a separate earth right back to the substation. Two have undersized neutrals as was historically normal. The one with the orange plastic bags in the photo shows hints of the steel tape armour over the lead, this has been removed on the others.Modern UK practice uses three core cables, often aluminium, with a combined neutral earth as copper loosely spiralled around the outside (lookup "wavecon") but N and E are always separated before they get to the consumer.

author: Monkeh
author_rank: Super Contributor
timestamp: January 24, 2020, 06:01:06 pm
content: Quote from: richard.cs on January 24, 2020, 01:51:02 pmVery nice - but I was thinking more the termination arrangement for a single-phase lead-clad cable as was once brought into properties.

author: IanB
author_rank: Super Contributor
timestamp: January 24, 2020, 07:22:33 pm
content: There doesn't seem to be much separation between the conductors in this cross-section? It looks a bit scary.

author: paulca
author_rank: Super Contributor
timestamp: January 24, 2020, 07:35:30 pm
content: Quote from: IanB on January 24, 2020, 07:22:33 pmWith such absolutely anal regulations beyond the utility cable in UK houses it is a bit a wonder how scary the distribution networks are.

author: richard.cs
author_rank: Super Contributor
timestamp: January 24, 2020, 09:32:54 pm
content: Quote from: IanB on January 24, 2020, 07:22:33 pmFrom memory it's about 3 mm of oiled paper around each conductor so 6mm total between them. I think it's partly that the copper is a bit bent from the cutting and partly that the size of the cable is not clear in the photo, I think it's about 60mm OD.

author: Electro Detective
author_rank: Super Contributor
timestamp: January 30, 2020, 10:22:01 pm
content: Quote from: IDEngineer on January 22, 2020, 07:17:57 pmAFAIK RCBOs here in Australia/NZ and the UK are a combination of RCD and MCB combined, usually in a single DIN slot package with active and neutral from the N busbar coming in,and active and neutral going out to the load/s.The RCD section work as they should to spec and easy to verify with a decent RCD testerThe MCB section, depending on the current curve (B, C, D, or anyone's guess sometimes..) reacts to short circuits and massive 5x > 10x current draw,but a bit of a fail on slow-ish thermal based gradual over-current.The 10 amp rated small breakers fitted to 4 way/6 way power boards/power strips work a lot better in that regard,once things get ~hot~ anywhere from 8 amps to 20 amps, they will pop reliably,whilst the 16 or 20 amp RCBO downstream fed with warm wire symptoms just sits there cluelessfwiw I use RCBO and power strip to cover all bases,and if I need a faster and or no brainer solution, a temporary in-line fuse to suit the load or DUT----------------------------How does the GFCI thing work with 120 and 240 volts over in the US?Do the separate 120 and 240 circuits have separate rated GFCIs, or go to a Master?What about 208v branches?I've seen Youtubers play with 120 <> 240 adapters to pull serious welder current or power homebrew -LightNing- rigsare they still getting GFCI benefits if GFCI is fitted?Will GFCIs in the US still work with a good centre tapped Neutral connection and failed Earth connectionand how reliably?More better worded questions coming once the coffee kicks in..

author: IDEngineer
author_rank: Super Contributor
timestamp: January 30, 2020, 11:23:59 pm
content: QuoteSame way. It looks for an imbalance in the current flow, which indicates a secondary path has been found (maybe YOU!), and opens the circuit(s).QuoteHere in the US you can buy single pole (one "hot" phase, 120VAC) and double pole (two "hot" phases, 240VAC), in a single unit with a single white pigtail connection to neutral.QuoteYes, as discussed ad nauseum herein, GFCI's do not rely on an earth reference to operate, reliably or otherwise. They need a neutral connection but not an earth reference. If neutral and earth are bonded then you could argue that the GFCI "has an earth reference", but that is a byproduct and plays no role in how the GFCI operates.

author: paulca
author_rank: Super Contributor
timestamp: January 31, 2020, 02:39:17 pm
content: Quote from: IDEngineer on January 30, 2020, 11:23:59 pmSo, explain why some of them DO have an earth reference.

author: richard.cs
author_rank: Super Contributor
timestamp: January 31, 2020, 02:57:08 pm
content: Quote from: paulca on January 31, 2020, 02:39:17 pmAll-mechanical RCDs operate on differential current only. The output of the current transformer directly drives the trip coil, the mechanism is sensitively balanced and quite delicate. These are vulnerable to sticking and modern ones often use the CT output to trigger a thyristor and dump a heavier current into the trip coil from the L-N voltage. These therefore don't work in absence of L-N voltage which becomes a safety problem if the neutral is open-circuit upstream of the RCD. A subset of this type therefore use a functional earth connection as a alternate place to pass tripping coil current to.In UK practice RCBOs are often half the width of an RCD, and sometimes do not switch neutral (this is a rubbish plan but very common). It may be that due the the space constraints these are more likely to have electronic tripping, but in any case it seems far more common for RCBOs to have a functional earth than for RCDs to have them. Also some RCBOs have earth tails that are essentially just there for EMC filtering.

author: IDEngineer
author_rank: Super Contributor
timestamp: January 31, 2020, 07:28:32 pm
content: Quote from: paulca on January 31, 2020, 02:39:17 pmThe better question would be why some have earth references and some do not. From their presence in the market and their acceptability to (at least) the National Electrical Code, we know that GFCI's without discrete earth references work just fine. So the question becomes why both types are available.I ran across a discussion of the optional discrete earth connection while replying earlier in this thread, but can't find it again right now. As I recall, GFCI's having discrete earth connections are able to detect yet another type of fault. If so, this would add another "choice" to the range of options in modern circuit breakers and you buy your device based on which of the following options you want: Overcurrent, differential current, arc detection, and now "earth fault" (whatever that last one means). But this thread has focused on the GFCI aspect of operation, and it's crystal clear that an earth reference is NOT required for that.

author: Monkeh
author_rank: Super Contributor
timestamp: January 31, 2020, 08:15:23 pm
content: Quote from: IDEngineer on January 31, 2020, 07:28:32 pmActually, certain people have latched onto such despite them not being the subject..

author: IDEngineer
author_rank: Super Contributor
timestamp: January 31, 2020, 09:07:42 pm
content: Quote from: Monkeh on January 31, 2020, 08:15:23 pmI checked back and you're correct. YOU first raised the question of breakers not operating properly in this response:https://www.eevblog.com/forum/beginners/how-is-neutral-wire-neutral-in-mains-electricity/msg2879446/#msg2879446...wherein you said:QuotePrior to that, references to breakers dealt with the OP keeping himself safe. Speaking for me, my comments had been limited to the thread topic, the neutral wire (and its relation to earth), until your query at me about breakers possibly not operating properly. Which I addressed because otherwise casual readers might be misled into believing that breakers require an earth reference, and it's dangerous to leave misinformation uncorrected when dealing with mains voltages.

author: Monkeh
author_rank: Super Contributor
timestamp: February 01, 2020, 12:28:49 am
content: Quote from: IDEngineer on January 31, 2020, 09:07:42 pmNow search long and hard for 'GFCI', 'RCD', 'RCCB' or 'RCBO' in my post.. I was referring to the function of MCBs, as not all circuits may require or desire residual current protection (unless you have a TT earthing arrangement - which you might well have created with your, uh, interesting approach to performing electrical work).

author: MadScientist
author_rank: Frequent Contributor
timestamp: February 03, 2020, 09:55:30 am
content: QuoteI think you are mixing up MCB with RCBOsAn RCBO is a residual disconnect device and an overload trip in one. They are very common compared to just RCDs. I’ve never seen an RCD or RCBO with an earth connection , what would be the point

author: richard.cs
author_rank: Super Contributor
timestamp: February 03, 2020, 10:30:14 am
content: Quote from: MadScientist on February 03, 2020, 09:55:30 amUK RCBOs are usually single-width to fit in the space an MCB would normally take up, and often have a functional earth tail. I understand other countries often have both double pole MCBs and RCBOs in double width, but we generally only have switches and RCDs like that. Commonly our RCBOs have a solid neutral connection, it passes through the device for residual current sensing but doesn't necessarily have a switch contact.Here's a couple of RCBOs with a functional earth connections (the thin white wire), in single-width the same as our MCBs:https://willrose-electrical.co.uk/product/hager-rcbo-10-amp-30ma-type-b-10a-106361-b10-adn-range-adn110/https://www.sparksdirect.co.uk/schneider-ez9d16810-easy9-10a-rcd-1-pole-neutral-6ka-30ma-type-b-rcbo-with-overcurrent-protection#.Xjf0h2j7SUkAs I said before the functional earth is used to sink current when the upstream neutral is O/C and an electronic tripping mechanism is in use (i.e. one where the differential current is a signal input but not the source of tripping energy).Quote from: richard.cs on January 31, 2020, 02:57:08 pmRCBOs are less common here compared to having a group of MCBs on the output of an RCD, like this:https://www.designingbuildings.co.uk/w/images/7/70/Consumer_unit_photo.JPG

author: paulca
author_rank: Super Contributor
timestamp: February 03, 2020, 02:33:43 pm
content: On RCDs. I asked the Spark who installed my RJ45 cables how much it would cost to put an RCD on my plug-ring and he said, "There is no point, that main RCD will always trip first."However, it turns out the main RCDs (in the UK anyway) are actually quite high current, 30mA / 30ms.I understand the 30mA is due to earlier much more sensitive RCDs nuisance tripping regularly and increasingly due to PCs and switch mode power supplies.Is it worth installing more sensitive RCDs in key areas such as my electronics bench and my fish tank?

author: richard.cs
author_rank: Super Contributor
timestamp: February 03, 2020, 03:07:52 pm
content: Quote from: paulca on February 03, 2020, 02:33:43 pmPossibly. If you installed 10 mA RCDs (the only widely available lower value in the UK) then tripping would occur at a lower current which might be desirable for some faults. If you were working on your bench and found yourself in a fault path with sufficiently high impedance that only 15 mA flowed (a painful but not usually harmful current) the 30 mA RCD would allow that continue indefinitely whereas the 10 mA one would trip within a few tens of milliseconds. In the majority of faults however the current would be >>30 mA and either or both RCDs would trip so you're not preventing the bench causing nuisance trips to the rest of the house.It sounds like you have a single 30 mA RCD covering the whole house? This is safe but a bit of a nuisance from a stray tripping perspective. There are other changes you can make to achieve discrimination, one example would be changing that one to a 100 mA time delay type and then putting separate 30 mA RCDs (or RCBOs) onto all the circuits that need 30 mA protection.

author: Monkeh
author_rank: Super Contributor
timestamp: February 03, 2020, 03:54:14 pm
content: Quote from: paulca on February 03, 2020, 02:33:43 pmDon't employ him again, he doesn't pay attention.Quote30mA is perfectly normal and sufficient to protect you. The 100mA device you have is not supposed to provide human protection.

author: SeanB
author_rank: Super Contributor
timestamp: February 03, 2020, 08:02:45 pm
content: With regards to that SWA cable, the same construction is used for 11kV, 33kV and 66kV cables, with only a small increase in the number of overlapped oiled paper insulating sleeve windings used. They do have a very robust overload capability, in that you can have the cable running for decades with the temperature at the melting point of the pitch pour in the seal, provided that your cable ends do not get wet during this time.I regularly see these in excavations, still powered, and with the pitch covering mostly gone, leaving the steel tapes exposed and corroding away, but the lead keeps it in more or less working condition, till it cracks and lets water in. Then the cable can and will excavate itself, I saw a failed 66kV joint, that blew itself out of the ground, leaving a 6m deep hole where the cable was buried, and turning the cast joint box into an art object. Current practise is not to lead wipe the joints, more due to the lack of any training on the art of lead wiping, and the older experienced people having mostly retired. Instead they use a cast resin joint, generally taking the paper cable to a PVC or HDPE insulated cable for further use, as it is something the electricians are trained to work with, though the core then changes from copper to aluminium in higher current uses, unless the length is short.As to RCD units, the type with a ground connection was used for a few years here, as the earth connection allowed the unit to detect the loss of supply neutral, tripping on loss of neutral using a 120VAC MOV device, and also incorporating a 480VAC MOV from line to earth as well, which meant you had to disconnect the outputs before doing insulation tests, and you could not back feed them.. the current approved types are smaller, and are strictly 2 wires in and out, and are strictly 30mA RCD, requiring external overload protection. Required on all socket outlets, so typically, as it is rated for use as a disconnector, it is the single main input breaker, so if it trips you are in darkness.Thankfully with the current Eishkom issues everybody has at ready reach some torches, a cellphone with torch or some form of lighting, as you will have regular rotational load shedding, and you might not get power back for a few hours to a few days if the bit turn on surge into a very cold load kills something upstream.

author: Electro Detective
author_rank: Super Contributor
timestamp: February 12, 2020, 09:54:17 am
content: Re RCD mA faith:If the fault current is high enough, fast enough and on a peaky? and or distorted top or bottom cycle/s, there is an extremely high possibilty that ALL the 10, 15, 30 and 100ma 'rated' RCDs will popBeen there, sometimes the 'faster ones trip first' thinking in theory and in practice ~works~ and you think you got it nailedbut on repeat tests under the exact same test 'fault simulation' conditions, the whole lot go off, and you never know wheni.e. it's unpredictable and not worth the embarrassment and inconvenience to assume a 10ma fast RCD will pop before the 30ma one at the switchboard 60 meters away.If you need your lab or bench 'RCD safe' and isolated from upstream/downstream RCDs, then that entire area/zone should be on an large-ish isolated transformer (aka 'Medical Isolation' style)with the Secondary earth/neutral/chassis bonded together, so the RCD can be plugged into that Seconday output and all the gear into the RCD via a power strip/s board/s etc.If TESTED and done properly with correct input and output polarity checked, the RCD will trip on faults or tests, but any RCDs elsewhere won't know or care.This is how I roll with suss scenarios or 'what ifs..'It saves on a lot of 'reset' walking in the dark with a flat torch, getting rained on, stepping on cat, dog, bird poo..again..and avoids mumbling feeble 'power failure/blackout' excuses no one buys anymore

author: richard.cs
author_rank: Super Contributor
timestamp: February 12, 2020, 10:16:23 am
content: Quote from: Electro Detective on February 12, 2020, 09:54:17 amThis is well known behaviour. Standard practice here (UK) is to use devices with delays as well as different currents. e.g. instant tripping (well, 40 ms or so) 30 mA devices, with a 100 mA device upstream which has a 100 ms delay, and then if further layers are needed 300 mA 300 ms, etc. It's the delay not the current rating that ensures they trip in order, the increasing trip currents are more about having multiple sub-circuits on each one. Only the <=30 mA instant trip types are considered to offer protection to humans.