Can't tell live from neutral, but wants to build 220V circuits. - Page 1
Forum section: electronics / general

author: Stonent
author_rank: Super Contributor
timestamp: June 08, 2014, 08:14:04 am
content: I was learning about Triacs today and the example was how to use a battery to control AC "mains" current using one. They even specifically say to make sure the battery is sharing a terminal with the neutral side only and not the other way around.Why do people even consider trying to get anywhere near working with household current if they don't know how to tell live from neutral?

author: mcinque
author_rank: Unknown
timestamp: June 08, 2014, 09:40:45 am
content: Well, I think because they don't minimally know what kind of effects their actions could have... Probably they ignore what they have on mains: "it's just a couple of volts and amps more than a car battery"

author: Bored@Work
author_rank: Super Contributor
timestamp: June 08, 2014, 10:05:34 am
content: Quote from: Stonent on June 08, 2014, 08:14:04 amWhy do you spend time reading such stuff? I mean, just at first glance you see that it is not worth reading. Stupid manga superpower figure. Use of "..". And the third strike, use of "???". NEXT.

author: Hypernova
author_rank: Unknown
timestamp: June 08, 2014, 10:58:30 am
content: Just relax, sit back and let Darwin work his magic.

author: rob77
author_rank: Super Contributor
timestamp: June 08, 2014, 11:30:29 am
content: Quote from: Hypernova on June 08, 2014, 10:58:30 am+1probably we'll be reading a nice story about it on the 2014 Darwin awards webbut joking apart... those kids are just stupidthey are arrogant and they just ignore the danger. i hope those kids will not kill or injure themself during the "experiments" with mains.. but i hope they will experience a decent bang and magic smoke which will teach them to have a decent amount of respect.

author: snipersquad100
author_rank: Frequent Contributor
timestamp: June 08, 2014, 03:35:34 pm
content: I wonder if people release magic smoke like caps.

author: rob77
author_rank: Super Contributor
timestamp: June 08, 2014, 04:13:55 pm
content: Quote from: snipersquad100 on June 08, 2014, 03:35:34 pmsure they doit's all about the amount of beans they consumefortunately that magic smoke is transparent

author: Kjelt
author_rank: Super Contributor
timestamp: June 08, 2014, 04:23:06 pm
content: You can argue the other way round, any circuit where it is vital that phase and neutral are known and it is unsafe when connected the other way round is just piss poor design with so many countries having a symmetrical poweroutlet system where you can not be sure what the phase and neutral are without measuring and marking it.

author: retrolefty
author_rank: Super Contributor
timestamp: June 08, 2014, 04:28:36 pm
content: In the US there is no 'neutral' on the 220 VAC circuits, just L1, L2, and a safety ground. In the EU (and any where else) do they actually connect one side of the 220 to ground at the service panel?

author: fubar.gr
author_rank: Unknown
timestamp: June 08, 2014, 04:51:38 pm
content: Quote from: retrolefty on June 08, 2014, 04:28:36 pmIn the US the neutral is the center tap of the distribution transformer which is also grounded.

author: retrolefty
author_rank: Super Contributor
timestamp: June 08, 2014, 05:03:05 pm
content: Quote from: fubar.gr on June 08, 2014, 04:51:38 pmYes, the U.S. homes it's a 240 vac 'split-phase' service, but the grounded (at the service panel) neutral is not routed to the 240vac load circuits, just the 120vac load circuits get the neutral and one of the 'L' phases run to them, along with a safety ground wire.Again my questions was do other countries that only use 240vac load circuits, is one side grounded at the service panel?

author: Zero999
author_rank: Super Contributor
timestamp: June 08, 2014, 05:08:20 pm
content: Quote from: retrolefty on June 08, 2014, 05:03:05 pmMost 240VAC countries distribute the low voltage power as 415V three phase with most domestic consumers only get neutral and 240V phase.

author: mtdoc
author_rank: Super Contributor
timestamp: June 08, 2014, 05:08:43 pm
content: In the US, 240V residential power uses 3 wires: L1, L2 and Neutral. The neutral is usually bonded to ground (earth) at the service entrance. 240V between L1 and L2. 120V between L1 or L2 and Neutral.

author: mcinque
author_rank: Unknown
timestamp: June 08, 2014, 05:12:31 pm
content: Quote from: retrolefty on June 08, 2014, 04:28:36 pmNo. AFAIK any metal chassis it's only and mandatorily connected to the earth ground.You must take in consideration that only here in Italy and in South Africa we're so "smart" to use a socket that can be reversed. A MAN cabling would be a trouble.

author: Bored@Work
author_rank: Super Contributor
timestamp: June 08, 2014, 05:17:14 pm
content: Quote from: retrolefty on June 08, 2014, 04:28:36 pmThe American split-phase system is rather unknown. It is actually a single phase system. Depending on who you ask, either the three phase TN-C-S or the three phase TN-S system is the most common in Europe.In both cases you get three phases L1, L2, L3 plus separate N and separate PE at your house distribution panel. The difference is that for TN-S the N and PE are only connected at the power source (transformer) and from there on carried separately. While for TN-C-S the N and PE are one combined wire (PEN) coming from the power source. At some point during the transmission (e.g. late at the service cut out) PEN is split into a separate N and PE.PE is earthed at a central point in the house, where also the water and gas piping is connected to.

author: retrolefty
author_rank: Super Contributor
timestamp: June 08, 2014, 05:18:34 pm
content: Quote from: Hero999 on June 08, 2014, 05:08:20 pmBut is that neutral bonded to ground at the service connection? If not it would be better named common rather then neutral.

author: retrolefty
author_rank: Super Contributor
timestamp: June 08, 2014, 05:21:43 pm
content: Quote from: Bored@Work on June 08, 2014, 05:17:14 pmSchematic drawings of these different systems (including U.S.) might make it all clearer?

author: mcinque
author_rank: Unknown
timestamp: June 08, 2014, 05:37:10 pm
content: Quote from: retrolefty on June 08, 2014, 05:18:34 pmQuote from: mcinque on June 08, 2014, 05:12:31 pmwe do not bond to ground neutral, because we have reversible plugs: with the wrong orientation of the plug in the socket, we would bring the live on the metal chassis of our devices.

author: fs
author_rank: Unknown
timestamp: June 08, 2014, 05:38:25 pm
content: Quote from: retrolefty on June 08, 2014, 05:21:43 pmhttps://en.wikipedia.org/wiki/Earthing_system

author: retrolefty
author_rank: Super Contributor
timestamp: June 08, 2014, 05:56:33 pm
content: Quote from: fs on June 08, 2014, 05:38:25 pmThanks you for that.

author: SeanB
author_rank: Super Contributor
timestamp: June 08, 2014, 06:14:55 pm
content: That socket is a recent addition, and is typically only used for double isolated equipment, like phone chargers and other 2 pin devices. You only get the earthed version in a wall outlet version that also includes the regular 16A 3 pin outlet as well, and I have never seen an extension cord for that that is not integral to equipment or is only for double insulated equipment. As well it is mandatory on all installations to have earth leakage protection on all socket outlets, irrespective of age. You can have a house with fuse wire on the board and a small box with the earth leakage breaker next to it, and it will be passed so long as the wiring still meets minimum insulation levels ( good luck doing that with 50 year old DCC wire though, there you will rewire in all probability) and you still have the original 5A and 15A outlet sockets and nothing added over the years. Any new stuff has to comply with current standards.

author: IanB
author_rank: Super Contributor
timestamp: June 08, 2014, 06:28:54 pm
content: Quote from: retrolefty on June 08, 2014, 05:18:34 pmEvery country has different systems. In the UK a 240 V socket in a house has L, N and E connections. Live has 240 V on it relative to Earth. Neutral and Earth are bonded where the supply enters the house and Earth is bonded to all water pipes and gas pipes and other exposed metal fixtures. There is a low impedance return path from L to E such that a short circuit between them will blow a fuse or trip a breaker.

author: FrankenPC
author_rank: Unknown
timestamp: June 08, 2014, 06:32:50 pm
content: Quote from: Bored@Work on June 08, 2014, 05:17:14 pmWhat's the exact difference between N and PE? A slight difference in impedance characteristics?

author: IanB
author_rank: Super Contributor
timestamp: June 08, 2014, 06:37:48 pm
content: Quote from: FrankenPC on June 08, 2014, 06:32:50 pmPE is not supposed to have any elevated voltages on it. The neutral wire carries current and therefore will experience a voltage difference along its length. The earth wire must not carry any current in normal operation and therefore remains very close to ground potential.

author: retrolefty
author_rank: Super Contributor
timestamp: June 08, 2014, 06:40:22 pm
content: Quote from: FrankenPC on June 08, 2014, 06:32:50 pmThe important difference is that neutral is a current carrying conductor, where as PE does not carry any current until a fault condition arises.

author: nitro2k01
author_rank: Frequent Contributor
timestamp: June 08, 2014, 07:53:02 pm
content: Quote from: mcinque on June 08, 2014, 05:37:10 pmI think you've misunderstood. See the above posts. Neutral and protective earth are not connected in the plug, but down in the distribution panel. PE normally doesn't carry current, and if you have a fault, the RCD will trip. The German schuko plug, probably used in half of Europe, is also reversible and works like this.And even if this weren't the case, how would a wrongly inserted plug translate to any danger? Let's assume one of the conductors was connected to the ground in the distribution panel (neutral) and this conductor was connected to the center hole and one of the other hole. This is what they did in Soviet and it's not optimal, but it more or less works. The chassis would always be connected to the center pin which would always be connected to the "safe" wire in the outlet. Reversing the plug (which would have to have 3 wires.) would reverse the polarity of the voltage supply to the machine, but never connect the chassis to live.

author: kolbep
author_rank: Frequent Contributor
timestamp: June 08, 2014, 08:12:42 pm
content: SeanB,With the recent changes to SANS10142 (ADMT, you can have a loophole on Insulation Resistance tests , just get the customer to plug a Computer or Medical Device into the socket, then make use of the following loophole :Insulation Resistance Testing:NOTE 2 In the case of existing installations where the power may not be switchedoff from certain circuits in order to carry out this test, the fact that the circuits aresubject to the supply voltage can be regarded as evident that the insulationresistance is compliant. Amdt 8----But to anybody that wants to exploit a loophole like this, remember, it is your a*se if you pass the compliance, and a fire breaks out, or if somebody gets killed because you took a shortcut. And anyway, if you do the proper testing :1) You can be sure that the Insulation Resistance is good, or2) You have a business oppertunity to make money replacing the cablesQuote from: SeanB on June 08, 2014, 06:14:55 pm

author: rob77
author_rank: Super Contributor
timestamp: June 08, 2014, 08:13:43 pm
content: Quote from: nitro2k01 on June 08, 2014, 07:53:02 pmactually the CEE 7/5 socket is used in half of the Europe - it has 2 variants CEE 7/5 type F (German Schuko) and CEE 7/5 type E (French). but all the new plugs are made compatible with both type E and F sockets.advantage of type E (French) is the fact the plug can't be inserted reversed like with type F (Schuko) socket.

author: GeoffS
author_rank: Unknown
timestamp: June 08, 2014, 08:48:31 pm
content: In Australia, the neutral is connected to ground at the premises switchboard (service panel)Earth is a large metal stake in the ground somewhere near the switchboard although in older houses it may be connected to the water pipes.

author: FrankenPC
author_rank: Unknown
timestamp: June 08, 2014, 08:56:36 pm
content: Quote from: IanB on June 08, 2014, 06:37:48 pmAh! Ok. It's literally THE potential path at all times VS PE which should only be intermittent under ideal conditions. Makes sense.

author: Lightages
author_rank: Unknown
timestamp: June 08, 2014, 09:22:23 pm
content: Quote from: mcinque on June 08, 2014, 05:12:31 pmWe use that same idiotic plug here in Chile too. The difference is that we also have a neutral! So you never know if you are plugged in the right way or not. I have taken to marking all my outlets and plugs to make sure they are the same. It is absolutely insane to use a system like we have here.

author: deth502
author_rank: Frequent Contributor
timestamp: June 08, 2014, 10:26:30 pm
content: Quote from: GeoffS on June 08, 2014, 08:48:31 pmsame in the us, only is many times connected to both ground rod and water pipe.funny thing in the us, for the most part (99% of the time, there may be a few exceptions) every single phase mains line going into a residential or single phase commercial building has 3 wires. L1, L2, and the gnd/neutral. with again, nutral and ground for the household wiring connected in the box, HOWEVER, it is illegal to run a wire out of the service pannel without a separate gnd and neutral wires. even if your feeding a sub-panel, designed to take a 3 wire service cable, if it comes off of your main panel, it MUST have 4 wires.

author: rob77
author_rank: Super Contributor
timestamp: June 08, 2014, 10:46:39 pm
content: Quote from: deth502 on June 08, 2014, 10:26:30 pmthat's exactly because the ground wire MUST NOT carry current. imagine your sub-panel connected with a common neutral/ground - under load the ground in your sub-panel will be few volts above the ground in your service panel (voltage drop acros the wire) and it's not a regular ground anymore.if you have dedicated ground wire , then the ground in your sub-panel will have the very same potential as the ground in the service panel.the fact that there is a common ground/neutral in the service panel (or distribution panel or whatever you call it) is ok, because that point is connected to a "physical" ground - burried metal plate, pipes...etc..

author: vk6zgo
author_rank: Super Contributor
timestamp: June 09, 2014, 04:33:03 am
content: Quote from: nitro2k01 on June 08, 2014, 07:53:02 pmYes,it is is no more dangerous than an Australian plug into a socket with the L & N inverted.(Until the 1970s,the now standard orientation was only a recommendation,so there may be some inverted ones around,still).In a "Single Insulated" device,it is the Earth (PE) which is connected to the frame/chassis,notthe Neutral,so inversion of L & N should have no effect.The only exception is in the old "Transformerless" Radios & TVs used many years ago in some countries,where one side of the Mains was connected to the device chassis.A reversal of L& N would make the chassis "hot" with respect to any earthed object,creating a shock hazard.When new,these devices were heavily insulated to protect the user,but old ones may have lost some of this protection."Double Insulated" devices do not care about L & N orientation,as their insulation is integral to the construction of the device & does not distinguish between the two Mains connections.

author: ejeffrey
author_rank: Super Contributor
timestamp: June 09, 2014, 05:12:14 am
content: Quote from: retrolefty on June 08, 2014, 05:03:05 pmYes. In parts of the world where 220-240 VAC is the standard outlet voltage one leg is neutral and the other is hot. They don't have an equivalent of the US domestic split phase distribution, at least not for general use.

author: vk6zgo
author_rank: Super Contributor
timestamp: June 09, 2014, 05:31:48 am
content: In the USA,Amateur Radio Operators are the most likely people to have plugin equipment for 240v,as legal limit Linear Amplifiers draw too much current from the 120v supply,limiting the output to less than allowed by the FCC.As far as I can see,most other use of the "split-phase" system is for washing maxhines,stoves,etc,all of which are either hard wired,or use a different,special socket.

author: miguelvp
author_rank: Super Contributor
timestamp: June 09, 2014, 07:25:09 am
content: Some washers, dryers, A/C units operate at 240 in the US, I have a 240 plug on the living room but never used it. It's next to a window so it probably was for an air conditioner.It's a Nema 6-20 plug

author: G7PSK
author_rank: Super Contributor
timestamp: June 09, 2014, 07:45:59 am
content: Not sure if this is in all US states but the few that I have visited the overhead pole distribution system uses the same neutral/earth wire for both the LT and HT. This I guess is fine as long as all earth's are OK but I could see a situation perhaps due to drought where some of the earth's/grounds are not as good as the should be and therefore a somewhat elevated potential on the neutral earth line.No doubt this is where someone shoots me down in flames, but by using the same line for both sides of the transformer it effectively becomes an auto transformer, non isolated.

author: rob77
author_rank: Super Contributor
timestamp: June 09, 2014, 08:52:22 am
content: Quote from: ejeffrey on June 09, 2014, 05:12:14 amactually we have it for general use , it's 400V 3 phase using a 4 pin plug (or newer 5 pin plugs). you will not find that one in apartments, but a lot of houses have it to power some "heavy gear".

author: Kremmen
author_rank: Super Contributor
timestamp: June 09, 2014, 09:56:14 am
content: Yes, commonly used for e.g. freshwater pumps (wells), semi fixed power tools etc. I have in my hobby shop a 3 phase table saw, lathe, cnc mill, plasma cutter and other stuff. In the woodshed there is a bigger circular saw for cutting firewood to length and so on. All buildings have at least one 3 phase outlet on the outside wall, garage and woodshed a few inside as well. On numerous occasions it has been very practical to plug in a heavy 3 phase extension cord and a worksite outlet box on the other end. That way you can share several 1 phase outlets between the phases and run several heavy tools at the same time without worrying about overloading the circuit protectors.