living on both sides of the Atlantic and being an electrical engineer and tinkerer I know this pretty well. One thing I would mention is that the American system is polarized while the European system is not.
What I mean by polarized is that in the USA, plugs and sockets etc are made in such a way that you cannot mix the hot and the neautral wires. The outlet has a wider blade for the neutral and you cannot flip the the plug around 180 degrees and invert them.
In continental Europe, OTOH, the plugs are symmetrical and will go in both ways which means that either your appliance has a double pole switch (and most don’t) or you have the risk of the switch interrupting the neutral rather than the live wire. I do not know why they did this when it is so obvious.
In America the neutral is always connected to the outer part of a lightbulb socket but in Europe you might have it connected to live phase and get a shock if you touch it.
In the UK I believe the have gone to the other extreme and have plugs with a triangular configuration which are so big they often weigh more than the appliance itself.
In this regard the American system is definitely superior and I do not understand why the European system is not polarized when, being twice the voltage, it is four times as dangerous.
The 220 volt with a center tap used in the US is not used in Europe where you have 220 volt between phase and neutral and 380 volt between phases but 380 volts single phase are never used in domestic appliances AFAIK.
This site has information of the electric, TV, standards world wide.
casdave, we [USA] have a ground, its a metal pole that goes into the ground about three feet. It’s connected to the ground wires of electrical plugs. Seems simple but I see this metal pole just about everywhere & all our plumbing is connected to it.
So the gas guy came, connected his meter to the ground pole & got a reading of about 7-12 volts up & down. So, if you’re in a bathtub & touch the faucet, you’d get a shock. Thats what happened.
Here’s a little more in-depth on the US wiring colors. cornflakes had it basically right - those colors are the most common for ROMEX, but there’s a little more:
Ground = Bare or Green
Neutral = White or Gray
Hot = Any other color, sometimes even striped
I only know basic house wiring since most of my work was industrial and commercial, but the color coding is the same.
Continental European domestic supplies are somewhat worrisome.
They have the notion that if their system is earth free then you cannot get a shock to it and both wires are live as such there is no true neutral.
It must be interesting to get an earth fault because no current would flow and you probably would not know anything about it, until you got the second one and you would have an earth loop circuit, I just don’t even want to think about it.
Our system permits the use of residual curent circuit breakers.If there is no earth leakage then the live and neutral currents will be equal, these are compared within the breaker device, any fault and they operate.
They are incredibly sensitive and it is almost impossible to get a fatal shock to earth using one.
Your system doesn’t seem to be able to offer this facility so I guess you use the volt drop system for similar breakers.They are not as sensitive IIRC.
Cornflakes
Not only is our voltage more likely to be lethal but our mains frequency is too, apparently our 50Hz is just the right frequency of supply to send your heart into fibrillation so evne a small shock can be fatal.
casdave, your residual circuit breakers sound like our Ground Fault Circuit Interrupters (GFCIs). The same idea applies: if the neutral and hot currents differ by more than a few milliamps, the GFCI will trip. Since these are only required in kitchen, bath and outdoor circuits, GFCIs are typically made as part of a wall receptacle, allowing a reset at the source. You can buy GFCI breakers though, which install in the service (breaker box.)
Wow. Theory is nice, but I find it hard to believe that the island’s entire power grid is assumed to be completely floating from ground. Any idea how this is done, capacitive coupling, perhaps?
Re: 50Hz v 60Hz, at least were not dealing with DC. In theory, if you grab a wire, you might have a chance to let go (or so goes the story around here; I’m not sure how much truth there is to it.)
Say, how many sdmb guys does it take to change a light bulb? Leave it to us to complicate the hell out of a simple light fixture change! We got a parallel thread of differences between U.S. and British power (I won’t even get into Navy shipboard power unless you like UNgrounded systems!) Anyway, I just wanted to throw in another possible explanation of why our friend got shocked on the neutral. Being in the business, there isn’t anything quite like the experience of a jolt from an open neutral; that is, a splice of three or more neutral wires. If you ever have this, do your best to keep the wires together as you add another neutral. Also, hook the neutral up before the hot when installing your fixture, otherwise you can backfeed on the neutral you are hooking up. This can be especially nasty with flourescent lights. Pleasant Wiring!
Casdave, we are supposed to fight ignorance here, not disseminate it. I believe eveything you have said is flat-out wrong. Can you tell me in what place and country of Europe or elsewhere you have seen ungrounded power grids?
European residential standard is 220V (phase + neutral from 3 phase 220/380 volt) as I have explained before and the neutral is always grounded. Differential switches (called CFCI in the USA) are very common everywhere and mandatory in new construction.
So can you tell me where you get your information?
Thanks for all the info. BTW, I apparently wasn’t clear. I was shocked on the black (hot) side of the circuit. It may have been the neutral, but it certainly wasn’t ground.
Flourescent, I’ll stay away from. I’d rather not get knocked off the ladder.
I didn’t call the owner of the house because his responsibility ended by providing me with a light fixture. I just happened to like my light fixture better. He doesn’t even know I changed it. (Hey, nobody tell, okay?)
BTW, years ago I lived in an older home with two-prong outlets. I had to get those little adapters and ground them to the screw on the utility box. The only 110v outlets the electrician grounded were the clothes washer, rifridgerator, and dish washer. Of course, the big 220v outlets for the clothes dryer and air-conditioner were also grounded
When I buy something that is European made I find it has a flat two pin plug neither pin of which is earth.
They look somewhat like the two-pin shaver socket outlet plugs.
In addition if you were to look in the IEEE 16th edn wiring regs book there are illustrations of differant types of incomer wiring configurations which are given letter codes.`
This is what the regulations have to say–
In the UK the most common methods of supply are TN-C because it is cheaper to employ and TN-C-S where this is not possible.
For overhead lines such as to remote points like farms then TT system is employed
but
You will not find an IT system in the UK except in special earth-free zones and these are subject to very tight rules indeed. The only reason it has been included in these regulations is to harmonise methods of working within the EU.
There are certainly parts of Europe that do use such a system, how much I do not know.
I do know that they do not use residual current trip devices because of this but instead voltage driven ones(can’t remember the correct name right now) but these were used in the UK some time ago and we dropped them after a fairly short time, they are not as sensitive.Word was that with the voltage safety trips you could get up to 70v into you before they tripped(on a 220v system that is)
I had better point out that for the regulations live parts of the cicuit include all parts of the circuit that normally carry current this, of course, includes neutral.
And just in case…exposed-conductive-parts means any part of an electrical appliance which is capable of carrying current in fault conditions but which forms no part of the normal circuit and which you can touch during normal operation.
Casdave, you need to travel more or get better information. Plugs with flat pins are American and not European, lets start with that. They are A and B on this page while continental Europe uses C and F with round prongs (I believe the standard was originally German).
I will repeat your quote:
And I repeat this is flat out wrong. They do not have such notion. I stand by my assertion that European power systems have the neutral grounded at the power transformer, just like the British, and I challenge you or anyone else to prove otherwise. (I am not saying it cannot exist but I am saying it would be extremely rare) I have never seen anything else anywhere.
This is not to say that the code would not allow it under special circumstances but what you say about British systems is equally applicable to continental Europe for the same reasons.
And to say “they have the notion that if their system is earth free then you cannot get a shock” is ludicrous. You really think there are no electrical engineers in Europe?
For the last 12 years I have divided my time between Europe and North America and I am an electrical engineer familiar with (but not an expert by any means) the US Electrical Code, American Boat & Yacht Council (ABYC) Standards & Recommended Practices for Small Craft (Safety and grounding on baot installations are very important and tricky and you have to know what you are doing), and with European installations residential and industrial.
Both the European and American plugs derive from the earlier ones with no ground and the newer grounded ones were made to be compatible with the old ones. You can still plug an old, ungrounded (two prong) plug into a newer grounded (three prong) outlet.
All new appliances will be grounded except in certain cases allowed by code. For example, small appliances that meet certain requirements of insulation. The power pack for my laptop has no ground because it is listed as a Class 2 power supply and the insulation between input and output is considered sufficient. (My tower OTOH is grounded.)
As I explained before, the US system is polarized (which I think is better) while the EU system is not (Which I think it has more reason to be given the higher voltage).
The Brits, having to be different from everyone else, have devised their own system of plugs, incompatible with everybody else’s and so cumbersome that their plug is as big as the adapter for my laptop.
My ideal power system would have:
American plugs and outlets because they are the smallest and most convenient and have the added safety of being polarized.
220 Volt because 110 just isn’t enough (so American homes have 220V anyway… just get rid of 110).
Frequency: This gets tricky… both 50 and 60 Hz are holdovers from very old times. Today we could go to 400 Hz (aviation standard) and save a millions on transformers etc. But the cost of the switch would be enormous so… we stay with what we have. It could be 300 Hz (to make it multiple of 50 and 60 and build appliances for a while that would work on both frequencies. (Solid state converters…)
But, getting back to the point and summarizing: I reiterate that you are wrong in your assertion which I quoted above and would like to see any proof that supports it.
I never said you cannot get a shock on an earth free system
I said you cannot get a shock to it ie - earth
But you obviously can get a shock between points of differant potential.
Ah, rereading my last post I realise what I intended, the plug itself is flat should read,
A flat plug with 2 pins. Yes that was not very clear at all.
Still, neither of them is an earth.
You notice I say that there is no true neutral, a differant way of saying that they are non-polarised.
I also doubt they can carry much current since they are small (compared to ours)
Our plugs act as a fuse carrier too which make them larger those fuses are from 3amp to 13 amp.Our final circuits for wall outlets are usually fused at 25-40 amp.
Years and years ago we used to have no fuses in the plugs but the fuse box was only either 5amp or 15amp.
I have no idea what the fuse rating is for wall outlets in other countries but if it was anything like 40amp then a partial short of say 30 amps in a small appliance rated at less than 3 amp might well be in danger of melting the flexible lead and causing a fire, and a total short circuit might cause an explosion, at least the fuse in our plug would go first.
In fact to use non-fused plugs we would, under our regs, have to use a flex capable of withstanding the the max fuse load+25% or max possible short circuit current until the box fuse blew(whichever worked out the largest cable) which would mean the flex would have to be very thick.So how do others get round that one.
As for where I got my information, that came from the -
IEEE Wiring regulations for electrical installations 16th edition 1991
All UK electricians work to it though it only covers supplies below 415v so grid is not covered.
I was told at nightschool that the IT system was used on poles to farmsteads in Europe but since I’ve no first hand experience I cannot verify, besides which many farms use huge amounts of power and so generally are on transformers of their own.
In the US, the plugs aren’t fused, the over-current protection (usually a circuit breaker nowadays) for the entire circuit is at a panel. All wiring for the circuit must be rated for the breaker current. For example, a 20 amp circuit of outlets would have a 20 amp breaker, and at least 12 AWG wire.
Casdave, a system being grounded and the plugs being polarized are two entirely different and unrelated things and I did not mean to link them in any way.
Anyway, I can assure you the power supply in Europe is grounded just as it is in the UK.
American plugs I believe are rated 15 or 20 amps which would cover most appliances (especially if they used 220 V). The upside is that they are small and convenient. The downside is that you need a different plug for higher amps.
25 - 40 Amps at 220 volts seems a bit excessive for household outlets (but, of course, it’s nice if you have it). I can only see the need in specific outlets for specific appliances or for heating. In the US these use different type plugs.
To have to carry such a huge plug in the UK for some tiny appliance like my computer adapter (which uses something like 100 milliamps) does not seem reasonable.
And for massive and strange plugs check out the South African ones! They are somewhat like the British except with round prongs.
Back to the original question, I am convinced that black or not, the wires connected to the switch are neutrals. You can test this by checking both sides of your switched outlet to ground with the switch in the off position. If either side is hot, you have a switched neutral. I wouldn’t use that circuit for your dimmer, instead feed from the always hot outlet and use your own switch. The switched neutral outlet is a safety concern and I would recommend removing it completely.
