Electric shock from power supply (and how to fix it?)

[antonis]

The neutral should go to ground at the street supply transformer,

I'm pretty sure at seadi123 house Neutral & Ground are tight together INSIDE building.. 

[GibsonGM]

The neutral should go to ground at the street supply transformer,

I'm pretty sure at seadi123 house Neutral & Ground are tight together INSIDE building.. 

Yes.  In the panel the neutral and ground are tied together.  What comes in from the street are 2 lines, in the US they have 240 volts potential between them (Europe etc, 240V).   The ground is what separates them into two 120V legs, the 'sides' of your electric box.   

[Rob Strand]

A power outlet has two wires and an earth. One of the two wires should be Neutral.
The neutral connects to earth at the house, which also connects to a ground stake poked into the ground.

The voltage you see at the power point is single-phase.
The single-phase derives from a three-phase star or Y connection, which has 4 wires.
The street normally has 4 wires.  Your house might have two of four.

Further up the distribution system you only use three wires (there is no neutral) which is a three-phase delta connection. You convert from delta to star using a three-phase delta-star transformer.

http://www.ecmweb.com/sites/ecmweb.com/files/412ecm06fig1.jpg

https://qph.ec.quoracdn.net/main-qimg-0220fd65d02b4c6d48a809bb9f2c0d23

120V systems
http://www.neilorme.com/pics/deltawye_figure1.gif

240V system:
https://qph.ec.quoracdn.net/main-qimg-91d4688ec60d9cbab02471e38214ee57?convert_to_webp=true

You will notice that the voltages don't add in magnitude.
They add-up when you take the phase shift between phases into account.

[antonis]

Yes.  In the panel the neutral and ground are tied together.  What comes in from the street are 2 lines, in the US they have 240 volts potential between them (Europe etc, 240V).   The ground is what separates them into two 120V legs, the 'sides' of your electric box.   

You're right Mike but I've seen some old buildings with only ONE line coming from the street (actually from medium to low mains transformer) and that's the HOT wire..
(old school electricians used to call it "phase"..)

Neutral wire starts from main fusing panel where it's tied with Ground wire..
(there isn't any Ground wire inside the building - all sockets and other mains receptors are of 2-pin type..)

[anotherjim]

Sorry guys, but I ain't never seen a neutral used as or tied to earth in the consumer unit or fuse panel. Any Supply cable earth is not relied on at all or needed.

Here's why.
The input after the isolation switch/fuse should now go through a RCD breaker. This trips out if the current in the Live or Neutral differs significantly (20 to 30mA often). This will happen if either Live or Neutral connect to Earth. If the currents do differ, then some current is going somewhere else which must be Earth, since that path is completed back at the transformer by that Neutral connection. Can you see that if Earth and Neutral were tied together in the house, then this won't work properly? Also, this is why the main circuit breaker should be a double pole while the Load breakers only need Live side single pole.

Oh, and...

[GibsonGM]

This is a good piece of info to read on the subject, and references the NEC.  I'm not going to pee pee fight over where the gnd's connect in the breaker box...

https://diy.stackexchange.com/questions/1706/is-it-ok-to-have-mixed-grounds-and-neutrals-on-bars-in-a-breaker-box

I 'get' what you are saying regarding SUBPANELS, Jim...having '2 grounds' can REALLY mess up your day, as the resistance between them is not trivial.  Neutral must be isolated in a sub-panel.    Are you not in the US?  I have never seen a panel that looks like that, LOL!!!       Might be different laws/practices, too, perhaps?


I would not want to play with the old "one wire" system, antonis....!!  of course it works, but wow...just so unfamiliar that something bad would be sure to happen      

[anotherjim]

UK practice, which is the same as Europe (EU). We have a very lethal single phase around 230v rms and even more lethal 415v rms between phases of a 3-phase supply. So it could be that ours is a bit different to 110v countries.

I do sometimes wish that our AC outlets and circuit breakers all had double pole switching. With only the Live switched off, an accidentally earthed Neutral will throw the RCD and knock all your power off!

[Mitch Lee]

Fyi, this could also be a problem with the grounded prong of the 1/4inch connector inside the guitar and might need resoldering. The wires have prob become frayed/poorly connected. I had this issue before with a bass guitar resoldering the input piece fixed the problem grounding problem along with the buzz.

[Ice-9]

Jim, coming from UK I totally understand your consumer unit picture, I was a sparky years ago and am familiar with the 17th edition etc. I do have a hard time with USA wiring though, everything that has been explained to me about USA  mains just sounds dangerous and hit or miss, they seem to have 2x100V lines and sometimes the earth is connected to the neutral.
Are there any USA sparky's here that would like to explain your system properly. It might be fun 

[Rixen]

In New Zealand and Australia it is mandatory to link the Neutral and Earth bars together at the switch-board (as well as distribution transformer). MEN, Multiple Earthed Neutral. The reason is to provide a almost guaranteed low resistance for fault current and trip the breaker fast.

RCD's still work fine in this system, but are installed either on each circuit or one on every three breakers before the neutral(s) enters the neutral bar. RCD's and are also mandatory in modern installations here.

The high voltage, low current AC that can be present on switch-mode plug-packs as leakage can be fatal to electronics. Bitter experience.

[PRR]

> A power outlet has two wires and an earth. One of the two wires should be Neutral.

Not always.

I have learned that in Argentina they get fed Delta with ~~230V between legs, and this is what they feed their lights and appliances. *Neither* power wire is Ground or Neutral!

Ground (protective earth) is supplied (in newer installations), but is NOT sized to carry power currents. (Being two legs of a 3-phase, the line-to-Earth voltage is 127V.)

Stuff should NOT rely on either side of the line being groundy.

> I ain't never seen a neutral used as or tied to earth in the consumer unit or fuse panel.

Because you have only seen post-RCD systems?

Also because even before RCD, UK commissioning rules required a G-N high-volt test. In older CUs the sparky would remove the G-N jumper for this test. Today I see the G-N jumper is (by necessity) before the master RCD, which I also see is often outside the CU, near the meter. (I think you will evolve toward individual circuit RCDs, for the reason anotherjim mentions: one fault darks the whole house.)

> USA sparky's here that would like to explain your system properly. It might be fun

No. Every time I engage a UK tech on US/UK systems, it goes badly. BOTH rule-books are extensive, dense, arcane, and assumption-ridden. NEITHER of us can fully comprehend how it is done on the other side of the pond. The un-stated un-questioned assumptions lead to confusion, frustration, and irritation.

The US system is as safe as any other, safer than many. (If it were not, Canada would not be using 99% the exact same rules!).

The US system IS "victim" of history. We got into electric before good insulation was widely available. 100V seemed safer. Europe began electrification about the same time but not nearly as universally. Europe's lower installed inertia (and war losses) allowed (and demanded) safe use of more economic systems as improved insulation and plug materials came along in the 1930s and 1940s.

Neutral is "always" connected to Ground some-where. This is not a hard/fast rule, but a consequence of good practice and interpretation. WHERE the bond is (house, street) is not really our concern, because the wires are fat and 100'/30m one way or another makes little difference.

[Rob Strand]

I have learned that in Argentina they get fed Delta with ~~230V between legs, and this is what they feed their lights and appliances. *Neither* power wire is Ground or Neutral!

Interesting, I've never heard of such a system.
Some equipment would struggle to pass EMC without a mains earth.

100V seemed safer.

Probably a consequence of Edison's fear mongering.
US must roll-out a lot more copper.

The system we have in AU is 240VAC (I think they now call it 230VAC with asymmetrical tolerances) the safety aspects have been argued to death.   There's good and bad sides to it.   I must say the voltage and frequency here are pretty well regulated.   The US on the other hand is renown for brownouts and voltage variations.

[anotherjim]

Most European electrification began for a specific use other than general power. Often hydro generation for a railway and sold to the area along the line to make a bit more money. Then the system & voltage was whatever the railways engineer had selected and could be DC.

[antonis]

The input after the isolation switch/fuse should now go through a RCD breaker. This trips out if the current in the Live or Neutral differs significantly (20 to 30mA often). This will happen if either Live or Neutral connect to Earth. If the currents do differ, then some current is going somewhere else which must be Earth, since that path is completed back at the transformer by that Neutral connection. Can you see that if Earth and Neutral were tied together in the house, then this won't work properly? Also, this is why the main circuit breaker should be a double pole while the Load breakers only need Live side single pole.

That's exactly why you can't use RCD breaker in a consumer panel like the one I mentioned above.. 
(in your panel photo, delete all black lines, DP MCB breaker & blue button relay on RCD and use green lines as Neutral..)

So, main circuit breaker is a single pole (Hot/Live) and it works only for over-current protection..
(you can easily experience a nice electrocution untill main breaker "decides" to open..)

<I would not want to play with the old "one wire" system, antonis....!! >
Neither do I, Mike... 
(but someone have to be an authorised electrician engineer for upgrading such a mess so I can't fess up anything more in public..) 

[GibsonGM]

I re-wired my entire house (it came with 1930s early cloth-covered 2 wire, mostly).   Lucky for me (or IS it lucky??) where I live has no electrical codes; no requirement for inspection after you work.  In that situation, studying 'how it's done' is a really, really good idea, such as on 3-way switching etc.  Ultimately, if one is careful, it is MUCH better to have the new wiring than to leave the old...that's probably partly opinion, but I'll stand on it.

However, all that was required in my case was to remove wire runs and re-wire outlets, and for me to run a new line to my 2nd floor, which I wired as I constructed it.  It was very easy, and didn't require considering things like "is neutral connected to ground?", as whatever was in the panel (a new panel a previous owner had installed...) remained down-stream of my work.  Some runs were new and had ground, so I copied how they did it when replacing the 2-wire. 

The lights work, the LED tester says the outlets are done right, and it has been fine for a year now.         

[PRR]

> Probably a consequence of Edison's fear mongering.
> US must roll-out a lot more copper.
> The system we have in AU is 240VAC

Street to house, a bit more (but Aluminum). The main load is figured on 240V, same as yours +/-. There are however three wires, two full size and one usually full size or one size smaller. I have "100A service" as two 100A wires and a 80A support line; for 100A on single 240V you may have two 100A wires, about 70% of the total area used here. Supports and labor amount to about as much as the wire, so the cost difference can't be huge. (+/- local costs of Aluminum.)

It IS true that Tommy found fewer dead workers around <100V machines than >100V machines. This decision was set *before* the AC/DC wars, he was just selling juice. However the danger rises rapidly above 100V, and for economic reasons (size/cost of Copper) we have snuck-up 1/4 Volt a year to 125V area.

GFI (RCB) has been a big help for frayed wires around dirt and concrete.

> Some equipment would struggle to pass EMC without a mains earth.

The Argentine system has a PE. But neither Live wire is earthed. Good equipment *should* do fine this way. Similar to the German plugs, where you can't know which of the two power wires is more groundy.

> US on the other hand is renown for brownouts and voltage variations.

That is not my general experience.

At my workshop, voltage was a solid 117V unless I pulled a large load (I was on the far side from the PT). *Except* one year a backhoe ate one of two feeders into the city. We lived on a steady 109V for a while.

My last house was 128V, I called and complained, got a 124V which never varied. (I believe it had been over-tapped for an older feeder, which was replaced just before I bought the house.)

My current *house* sags, yes. But if my load is light, the voltage is *always* 125V solid. On heavy load I can dip below 110V, but my calcs on my too-long feeder say this is almost all in "my" wire (1% in transformer). I believe the wire was installed for a trailer, and never upgraded when the house was built. I can ask Hydro for a re-study, but they give the first 100 feet free, the rest would be my investment. Not worth it.

The US and the UK can't be quite compared, because the US grids are MUCH larger than the UK grids. Both in power and in distance. I am reading B.M.Weedy's classic book, primarily UK but with notes on the US, and it is apples to watermelons.

There *are* areas of the US where voltage is wonkier. And yes there have been supply shortages forcing cut-backs etc. Some of this is dying industrial cities which can't afford maintenance. Some has been really stupid government rate policy which invited suppliers to "game the system" to force artificially high rates. But many areas are as bad. Puerto Rico (of the US but not in the US) has been an economic disaster even before the recent storm. Brazil IMHO mis-prices its electricity for political favor. India tolerates massive stealing, again probably to prevent public outrage.

[Hatredman]

> Probably a consequence of Edison's fear mongering.
> US must roll-out a lot more copper.
> The system we have in AU is 240VAC

Street to house, a bit more (but Aluminum). The main load is figured on 240V, same as yours +/-. There are however three wires, two full size and one usually full size or one size smaller. I have "100A service" as two 100A wires and a 80A support line; for 100A on single 240V you may have two 100A wires, about 70% of the total area used here. Supports and labor amount to about as much as the wire, so the cost difference can't be huge. (+/- local costs of Aluminum.)

It IS true that Tommy found fewer dead workers around <100V machines than >100V machines. This decision was set *before* the AC/DC wars, he was just selling juice. However the danger rises rapidly above 100V, and for economic reasons (size/cost of Copper) we have snuck-up 1/4 Volt a year to 125V area.

GFI (RCB) has been a big help for frayed wires around dirt and concrete.

> Some equipment would struggle to pass EMC without a mains earth.

The Argentine system has a PE. But neither Live wire is earthed. Good equipment *should* do fine this way. Similar to the German plugs, where you can't know which of the two power wires is more groundy.

> US on the other hand is renown for brownouts and voltage variations.

That is not my general experience.

At my workshop, voltage was a solid 117V unless I pulled a large load (I was on the far side from the PT). *Except* one year a backhoe ate one of two feeders into the city. We lived on a steady 109V for a while.

My last house was 128V, I called and complained, got a 124V which never varied. (I believe it had been over-tapped for an older feeder, which was replaced just before I bought the house.)

My current *house* sags, yes. But if my load is light, the voltage is *always* 125V solid. On heavy load I can dip below 110V, but my calcs on my too-long feeder say this is almost all in "my" wire (1% in transformer). I believe the wire was installed for a trailer, and never upgraded when the house was built. I can ask Hydro for a re-study, but they give the first 100 feet free, the rest would be my investment. Not worth it.

The US and the UK can't be quite compared, because the US grids are MUCH larger than the UK grids. Both in power and in distance. I am reading B.M.Weedy's classic book, primarily UK but with notes on the US, and it is apples to watermelons.

There *are* areas of the US where voltage is wonkier. And yes there have been supply shortages forcing cut-backs etc. Some of this is dying industrial cities which can't afford maintenance. Some has been really stupid government rate policy which invited suppliers to "game the system" to force artificially high rates. But many areas are as bad. Puerto Rico (of the US but not in the US) has been an economic disaster even before the recent storm. Brazil IMHO mis-prices its electricity for political favor. India tolerates massive stealing, again probably to prevent public outrage.

You're Right about Brazil. Electricity prices here are a bit unrealistic.

Our system is sometimes similar to Argentina's, with two hots, no neutral, and an earth. Problem is, in more than 90% of buildings (including my house), The earth pin is simply left unconnected to save on wire.

I Said "sometimes" because it's not a sure thing. Some cities are "220", two hots and no neutral, only ground. Other cities are "110", meaning hot, neutral and Ground. Anything sold here that needs mains Power Must have a 110/220 switch. If you take your valuable 110V tube amp, go gig on a 220 Town and forget to Flick The switch, you WILL fry your amp.

There's absolutely NO inspection of New (or old) installations, so people just do what they want.

If you add The "I'm too lazy to ground my wall sockets" state of mind to The equation, you can start to understand why so many Brazilian guitarists still die from electrucution when they are holding the strings and grab The microphone...

.

[Rob Strand]

It IS true that Tommy found fewer dead workers around <100V machines than >100V machines. This decision was set *before* the AC/DC wars, he was just selling juice.

So there is a reason for it.

However the danger rises rapidly above 100V, and for economic reasons (size/cost of Copper) we have snuck-up 1/4 Volt a year to 125V area.

I've always wondered what the average (US) man in the street thinks mains voltage is; I've seen 110V, 115V, 117V, 120V.    The nominal voltage for consumer equipment seems to vary; maybe not nowadays.   I used to think it was simply different areas ending-up with different voltages due to loading effects.    It was a problem designing power supplies for US which used transformers.

My current *house* sags, yes. But if my load is light, the voltage is *always* 125V solid. On heavy load I can dip below 110V, but my calcs on my too-long feeder say this is almost all in "my" wire (1% in transformer).

I've came to the exact same conclusion in my house, the drop is in the house wires.  I can't quote the voltage drops because I rarely have to check it.  In general the street voltage is 240V, despite the now 230V rating.

That is not my general experience.

Interesting.  That's not what I've read over the years.  Maybe things have improved.

The US and the UK can't be quite compared, because the US grids are MUCH larger than the UK grids. Both in power and in distance. I am reading B.M.Weedy's classic book, primarily UK but with notes on the US, and it is apples to watermelons.

It's enormous!  and so many vendors.   We have large distances here but the larger loads are distant.


Has anyone is South America noticed small shocks from equipment with a mains earth pins?    especially things with metal cases and panels.  Some equipment, like desktop PCs etc, use the ground return for line-filters.
Not connecting the earth line is in effect like operating the equipment with a single fault (ie. no earth)
so if you do get a second fault the equipment might not be safe.

[anotherjim]

UK system was worked out during 1940's during WW2 to cater for the intensive rebuilding foreseen after bomb damage. 240v chosen to cut copper weight, also the use of ring wiring (every outlet has 2 cables for east and west connection to the fuse/breaker).

I've been pondering our reluctance to bond Neutral to Earth at the property. I guess UK engineers have it set in stone that Earth is for protection against exposed Live surfaces and it should do nothing else. However, one of the worst fault conditions is the 3-ph transformer Neutral feed breaking open somewhere downstream, although ground at the transformer can be expected to remain good. That allows interaction between all 3 phases according to load and the Live-Neutral voltage at a property can be anything from 0 to 415v. I suppose this "floating neutral" condition is mitigated if your Neutral is individually grounded? A danger of this is, as the Earth bond is only in a little part made of wire, large currents passing via Earth can cause a voltage lift at your Earth rod, and it isn't a safe 0v any more.

[antonis]

If you add The "I'm too lazy to ground my wall sockets" state of mind to The equation, you can start to understand why so many Brazilian guitarists still die from electrucution when they are holding the strings and grab The microphone...

I'm pretty sure these "happenings" are strongly encouraged by Brazilian Drummers Federation..