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| Paul_L Guru  Joined: 03/03/2016 Location: United StatesPosts: 769 |
@ Grogster - Yep, neutrals are never switched! The hot wire can be any color except green or white. Green is always ground, white is always neutral. Typical residential electrical service is 3 wire, usually Red/White/Black, 120/240 v 150 A or 120/208 v 150 A depending on geographic area and which way the individual utility company wires the secondaries of its final stepdown transformers. If the secondary is three phase with each single phase secondary winding producing 120 v then putting two windings in series produces 208 volts at a different phase angle from either individual single phase secondary. This is described as a "Y" hookup and is found in areas which were wired earlier in the 1900s like all of New York City where Consolidated Edison is the utility company. The common point of the "Y" is typically grounded at the transformer secondary and at the house entrance. The areas wired later in the 1900s mostly used secondaries wired in a triangle or "Delta" pattern where a single residence only receives power from one center tapped secondary so that 120v + 120v does equal 240v. The center tap of each of the three secondaries are grounded at the pole and at the house entrance. Paul in NY |
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Grogster Admin Group  Joined: 31/12/2012 Location: New ZealandPosts: 9610 |
Cool, thanks.  I expected as much. Apart from the different plugs and voltages, the danger of switching the neutral would still be the same no matter where you were I would have thought. Next question: If the switch is indeed in the Phase in USA, but you are on the old two-prong plug, plugging that in the wrong way around will have the effect of putting the switch in the neutral. Does the American code have anything to say about that? I am just curious about the American two-prong NON polarised plugs and sockets, cos most other counties use polarised plugs, and provided you have wired up the plug right, there is no way you can have the switch in the neutral line. I seem to recall seeing another kind of plug it is two ROUND pins - might be China or something, and it also would have the same issue, cos you can put it in either way around. Smoke makes things work. When the smoke gets out, it stops! |
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TassyJim Guru Joined: 07/08/2011 Location: AustraliaPosts: 6283 |
Europe has the two round pins. Depending on the device connected, they will have the two pins without any earth and non-polarised - double insulated things usually. Other devices need the earth and then it is (usually) polarised. It gets interesting when you are trying to sort out travel adapters. Jim VK7JH MMedit |
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MicroBlocks Guru Joined: 12/05/2012 Location: ThailandPosts: 2209 |
The most common in Europe is this one for small loads and has to be double isolated: Type C:  This the most common for larger loads and when grounding is needed: Type F:  In the Netherlands these are the only two that are allowed. The smaller one also fits in the socket with ground, bot not the other way around (ok, ok with some force it does. :) but only in very old Type C sockets. The newer one have smaller holes which prevents that). When using a Type F plug in a type C socket there is a shock hazard. The pins of type C are isolated on the top. This prevents children from getting shocked if your finger is in between. The metal parts in the socket are also deep so that when contact is made only the isolated part is exposed. This plug fits in grounded and ungrounded sockets. The socket for the type F plugs are recessed about 15mm to prevent a shock hazard.  Both plugs are not polarized! Pics from: https://www.worldstandards.eu/electricity/plugs-and-sockets/ http://www.iec.ch/search/?q=plugs Microblocks. Build with logic. |
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| JohnS Guru Joined: 18/11/2011 Location: United KingdomPosts: 4044 |
Just to mention that the UK is part of Europe (and as yet also the EU) but does not use those types at all. (Travelling to continental Europe I take a multi-purpose adapter.) Our mains voltage sometimes surprises (can be 250V whereas a lot of Europe seems to be 230V) and neutral here is roughly 0V. Not much point switching just the neutral here! Normally we switch both (or just L). John |
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| MicroBlocks Guru Joined: 12/05/2012 Location: ThailandPosts: 2209 |
Yes, the UK is and will always be different. :) :) Ring circuits and fused plugs..... Are ring circuits still allowed? How does a USB charger look like? Plug bigger then the device? And those plugs are perfect caltrops. :) But with all of that, they are i think the safest. And that is what counts. Microblocks. Build with logic. |
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| JohnS Guru Joined: 18/11/2011 Location: United KingdomPosts: 4044 |
I don't know the regulations but probably. I've never lived anywhere without them and they seem to cause no problems. I thought (guessed/assumed) everywhere would use them. (I believe there are rules about how many sockets/etc can be wired per ring and also about exactly what any one ring can be used for.) Yes plugs are each fused. Rings used to be fused in the old days but for years have used circuit breakers. I can't recall when I last had a fuse blow or circuit breaker trip. Many years. They "just work". Recent USB (mains) chargers are basically the plug more or less as usual and a USB lead from it. Works well. The UK plugs are very safe (e.g. for children) and can't be plugged in wrong. The sockets have spring-loaded shutters so again are safe for children. When I've stayed in foreign houses (quite often) I've often looked at their wiring, sockets (aka outlets), plugs etc and thought they look crude and nasty. I know we get very few fires or deaths due to electrical issues but don't know how we may compare per capita. John |
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| Paul_L Guru Joined: 03/03/2016 Location: United StatesPosts: 769 |
The only gadgets you'll find a non-polarized plug on these days are things like table lamps, electric shavers, and wall warts. In other words, anything which has an insulated case or totally isolated wiring. A light bulb with a switch in a table lamp doesn't provide much opportunity to come in contact with a conductor. The UL (non-governmental, written by insurance companies) electrical code doesn't say too much about portable devices requiring polarized plugs. If a portable gadget, like an electric drill, has exposed metal parts it must have a "U" ground plug which is automatically polarized. The UL code mainly talks about what you can install permanently in a building. For example, polarized GFI outlets with a "U" ground must be used in bathrooms and kitchens where you might come in contact with water pipes. A building owner is not required to retrofit polarized or grounded outlets in an old building which was wired up before the requirements for the "U" ground outlets came into existence. Virtually every outlet installed since about 1962 has a "U" ground. I don't think you can even buy non-polarized / non grounded outlets anywhere. You're right in that you can insert a non-polarized plug the wrong way round and have a switch, say in a lamp, in the neutral instead of the hot conductor, but the light bulb won't care and you can't reach the conductors. Paul in NY |
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Azure Guru Joined: 09/11/2017 Location: AustraliaPosts: 446 |
A lot of inline mains switches these days switch both live and neutral conductors to cater for such situations. That generally includes everything from the cheapest chines mains inline table lamp switch to high end German made lamps used for film production. It is usually older units with a mains switch in the product itself that only switch one line. In that case they try and switch the Active in the hope it is correctly wired. But as this thread suggests, on certain country plugs this can be accidentally and easily reversed. I have also repaired many items where someone has rewired and new mains plug incorrectly and has caused the neutral to be switched because they did not understand the original wire colour codes or bother to trace/meter which wires go through the one pole switch (usually when black and white coloured mains core leads are involved). |
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| Grogster Admin Group Joined: 31/12/2012 Location: New ZealandPosts: 9610 |
Indeed. Well, the old colour code for Australia/New Zealand and also England I think, was red=phase, black=neutral, green=earth. If you get something from America, the black is the phase, and the white is the neutral, so I can certainly see people from our neck of the woods assuming black is still neutral, and wiring up an American cord with black as neutral and white as phase.  Smoke makes things work. When the smoke gets out, it stops! |
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| Paul_L Guru Joined: 03/03/2016 Location: United StatesPosts: 769 |
Back in the 1920s when knob and tube wiring was being abandoned in favor of rubber insulated then cotton wrapped wires inside of spiral steel sheathing (BX) UL decided the easiest to see and most durable color for the cotton wrapping was white so that would be used for the neutral. It was not practical to color the rubber insulation itself until the 1940s. Paul in NY |
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| lizby Guru Joined: 17/05/2016 Location: United StatesPosts: 3378 |
I recently worked on renovations to a house in Canada which had some old 2-prong wiring (120V). One of the outlets was broken, and it was not possible to purchase a new 2-pronged one. The solution was to add a GFCI outlet (which in this case could be put near the fuse box (no circuit breakers)) for the entire circuit. Then you could replace the 2-prong with a 3-prong "U"-ground outlet and affix a sticker (supplied with the GFCI outlet) which said "No equipment ground". This apparently meets code in Canada and the U.S., and provides protection for persons, but none, for instance, for your $$$$ plasma TV (not that one is likely ever to be put in this dinky house). (The house was old enough that the floor joists were not sawn lumber, but bark-on logs with the tops flattened.) PicoMite, Armmite F4, SensorKits, MMBasic Hardware, Games, etc. on fruitoftheshed |
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| Paul_L Guru Joined: 03/03/2016 Location: United StatesPosts: 769 |
@lizby -- Were the old outlets US style flat blades or were they some variant of UK round pins? I know that the codes in Canada are now very similar to the US codes but I wonder if they were more like the UK codes back when the wiring was added to that old house. I've got an old house (circa 1790) in upstate New York where the structure is all hand hewn timber with the bark left on. It had electric wiring added about 1905, which was earlier by 10 years than the electric wiring in the house I grew up in located in Queens County in NYC. Some of that wiring is bare copper knob and tube tied to glass insulators and it is still live today. Most of it has been replaced with modern romex -- 3 conductor #12 awg with plastic insulation wrapped in a plastic sheath. Some of the knob and tube stuff is impossible to reach. Ah well, at least it's good for electrocuting squirrels and raccoons! Paul in NY |
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| Paul_L Guru Joined: 03/03/2016 Location: United StatesPosts: 769 |
In the US neutrals and grounds are NEVER supposed to be switched or fused. In modern circuit breaker distribution panels it's impossible to do anything else, the 120v busses hook automatically to the tile in circuit breakers and the neutral and ground distribution is through solid bus bars. Older electrical installations can use all sorts of weird individual screw in fuses with Mazda bases and they can be wired up in any possible incorrect way. Paul in NY |
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| Grogster Admin Group Joined: 31/12/2012 Location: New ZealandPosts: 9610 |
Are you guys allowed to put more then one wall outlet on a circuit-breaker? Here in NZ and Australia, it was very common to have up to three wall sockets on the same circuit-breaker, daisy-chained in a parallel circuit. I THINK the regulations have changed on that now - I am not an electrician, so don't stay up to date with the fixed wiring regulations. As an EST(Electrical Service Technician), it is illegal for me to work on fixed mains wiring anyway, which is another reason I don't bother keeping that much up to date on changes, as I can't work on that stuff anyway. I have several sparkie chums if I need an outlet fitted somewhere.Smoke makes things work. When the smoke gets out, it stops! |
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| Azure Guru Joined: 09/11/2017 Location: AustraliaPosts: 446 |
@Paul. I was referring to the appliance switch not the mains distribution. I agree mains distribution does not switch neutral. @Grogster, there are still several outlets per MCB/RCD (not sure how many it is at the moment). If every powerpoint went to a seprate MCB/RCD the switchboard (which is now a small din rail cabinet) would become very large quickly even for a small apartment. |
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| Pete Locke Senior Member  Joined: 26/06/2013 Location: New ZealandPosts: 182 |
Here in N.Z, the new requirement in industrial electrics is to break the neutral as well as the phase on RCD protected circuits. No need to upgrade existing installations, but anything new must comply. I deal mostly with 3 phase stuff at work, but every now and then single phase issues raise their head. Some, well most of the gear we have is from overseas and the internal wiring can take a bit of sorting with different colour/color codes. The live can be any colour you can think of, except green. We've had gear arrive with switched neutrals (how it made it through import to say nothing of the compliance certificate) that needed to be re wired to satisfy the regulations. All good fun. But back to the origins of the thread..... I bought some time ago a 30v 10a supply  Think it was off TradeMe or something similar. No current regulation. But that's only an issue to sort out "Back Shed" style. My Brother used to work for an outfit that had a contract, amongst other things, of changing out the light house lamps around the South Island. Nothing wrong with the bulbs, but as a preventative maintenance thing they were changed out. Guess were all the 'old' ones ended up . Bulbs...oops...Lamps are one of THE most useful limiters/fault indicators ever created. Wouldn't be a week go by when I don't have one in place of a fuse looking for a fault that would otherwise see you back to the board to put in another one. Wiggle the wires in the suspect area, the light glows letting you know you're close . Almost close enough to agree with the re badged amp meter in the supply |
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| lizby Guru Joined: 17/05/2016 Location: United StatesPosts: 3378 |
In the U.S. and Canada, a Ground Fault Circuit Interrupter (GFCI) outlet can protect multiple downstream (properly grounded) outlets. It is possible to use a GFCI circuit breaker in the breaker box to protect an entire circuit. As I understand it, the GFCI outlet will trip on shorted downstream 2-wire outlets because it recognizes the difference in current between the hot and neutral wires (so perhaps it should be a Neutral Fault Circuit Interrupter), but a surge protector will not work on downstream 3-wire outlets on a grandfathered 2-wire circuit because there is no ground to shunt excess voltage to. PicoMite, Armmite F4, SensorKits, MMBasic Hardware, Games, etc. on fruitoftheshed |
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