AH#14 - Electrical Work - Page 1
Forum section: electronics / general

author: JohnS_AZ
author_rank: Frequent Contributor
timestamp: November 03, 2010, 03:51:35 am
content: Dave, I just got around to listening to AH#14. You were talking about the restrictions on working on electrical (mains) power in AU, and asked what it was like in other areas...I've been building an In-Law apartment attached to my house for about 6 months. About a month ago it was time to deal with the power. The existing breaker box on the house was only 100 amps, and only provided 14 circuits. There were also some horrible (scary) changes made by the previous owner. I had corrected them when I moved in a dozen years ago, but now it was time to replace the whole thing.Long story short; I got a permit from the city ($125), started at 6:00am by killing all power to the house, ripped out the old box, opened up the wall, installed the new box (200 amp, 44 circuits), wired it all up and had the power back on by 4:00pm. Note: bending 00 gauge cable to fit in the box was a bitch! The city inspector came out and did a 5 minute inspection and signed me off. Done.To your question, I have no formal electrical training or certificates. Here (in Arizona anyway) if you own the house you can undertake virtually any kind of repair or construction you wish -PROVIDED- you get the proper permits from the city, and you pass the inspection of your work. Now I think it's safe to say that virtually no one actually does this level of project on their own, but the thing is, they could.Here's the picture I posted to Facebook of the work...

author: EEVblog
author_rank: Unknown
timestamp: November 03, 2010, 05:08:30 am
content: Cool.Technically I think you can do that here too, get an electrical to sign off on your work.I don't know how happy they are to do this though.Although I can design a full product with 240V in it (and an IEC connector etc), AFAIAW I am not allowed to attach a fixed 240V cable and wire up the mains plug on the same gear. Nuts.Dave.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: November 03, 2010, 09:18:49 am
content: Does anyone actually pay attention to the Aus rules Dave? Can you easily buy sockets, distribution boards etc. over the counter?Here in the UK, they added a section to the building regs a few years ago which meant that in theory all but simple like-for-like replacement needed to either be done by a registered 'competent person*' or notified (with fee) to council building regs dept.*Competent person basically mean they've paid a fee for membeship of a trade body.This all arose from some bogus statistics about electricity related deaths/injuries, but the figures actually showed the vast majority were due to faulty appliances! There is also a suggestion it was more about keeping track of tax evaders doing cash jobs.At around the same time they changed the wiring colours, which was completely unnecessary, but there was enough overlap between new colours being available and the rules coming into force (about a year) that you could easily claim that any work in new colours was done before the rules came into effect.You still often see ebayersselling reels of old colour cable!However in practice few people pay any attention to it. Even solicitors dealing with house purchase don't usually bother checking that the paperwork is in place. About the only time it's unavoidable is when new wiring accomapanies new building work that comes under other building regs.

author: scrat
author_rank: Frequent Contributor
timestamp: November 03, 2010, 10:18:52 am
content: Here in Italy rules are quite strict, only technicians could do any work on the electrical system. However, as in other places no one cares, except for the new buildings.The majority of houses built before 15 years ago have no technical paperwork about their systems, and having one will cost thousands of €uro even if no concrete work has to be done. The situation is worst here (because of the earthquake in 1976) and in the areas where tax evasion is more frequent.If the Government would seriously start to make controls around, I think there will be a rebellion.While before the changing in University regulation an engineer (5 years degree and registration after an exam) could make any kind of project (for example, an EE could virtually design a house), now we are only allowed to work into our area, which in my case is Information EngineeringThis results in the fact that I can't sign a photovoltaic system (even if I work on inverters), but a mechanical engineer can!I think the safety level in electrical systems and appliances is orders of magnitude over other areas (transportation, for example), maybe somewhere excessive. For anything electrical it is required that a stupid can handle it while sleeping, but if you drive a car, even if you pay maximum attention you can have an accident.

author: EEVblog
author_rank: Unknown
timestamp: November 03, 2010, 10:35:01 am
content: Quote from: mikeselectricstuff on November 03, 2010, 09:18:49 amYes, you can buy sockets, power points etc at the local hardware store. They are all marked with "must be installed by a licensed electrician" etc.No one really pays much attention to the small stuff, but few would wire their own home etcDave.

author: PetrosA
author_rank: Frequent Contributor
timestamp: November 03, 2010, 12:37:16 pm
content: Generally in my area you aren't allow to do anything yourself, but the level of enforcement varies. The City of Philadelphia is very strict - to the extent that if anyone, at any time, has done electrical work without a license and inspection in a house the violation follows the subsequent owners down the line (i.e. if you get something done in a house you just purchased and the inspector finds things done illegally by a previous owner, it's now your problem).As an electrician, it's obviously in my interest to argue for a system that doesn't allow people to do their own work. In practice, I don't have an issue with people doing things themselves provided they know what they're doing, and that's the problem most of the time. Some of the most dangerous homes I've worked in have belonged to Boeing engineers (there's a Boeing facility nearby). Overloaded circuits - energized enclosures, boxes and light fixtures - ground wires used as neutrals - these are all things I've seen done by engineers. Part of the problem is that the more someone thinks they know, the less likely they are to ask advice and the more likely they are to create a life threatening hazard. One example would be a fluorescent shop light I saw recently in a basement. The homeowner (not a Boeing engineer...) had wired it into the mains with lamp cord (no ground) and somehow connect the frame ground wire to the hot wire on the lamp cord inside the light. When they had their bathroom remodeled, the plumber cut the floor open to solder the pipes to the tub, reached in and made contact with both the copper pipes and the light fixture. luckily, he was able to pull away in time, but I hate to think what could have happened. The price for mistakes can be high, and might be paid by someone else. Keep that in mind and be careful PLEASE!

author: scrat
author_rank: Frequent Contributor
timestamp: November 03, 2010, 01:14:20 pm
content: Some of the bad things described by PetrosA are impossible to do if a differential breaker is used. Isn't is mandatory? It doesn't cost so much, and saves life most of the times.

author: JohnS_AZ
author_rank: Frequent Contributor
timestamp: November 03, 2010, 03:03:01 pm
content: Dave, what's a "power point"? Must be an AU term for a socket or breaker.Scrat, is a "differential breaker" the same as a GFI? If so code here requires the use of GFIs on any circuit with a socket in a wet area (bathrooms, kitchen counters, etc), or any sockets on the exterior of the house.I only have two real gripes with the system here.First, they should have all the building codes on line for free. If you're going to hold me to a set of rules, you should GIVE me a set of the rules. Not make me buy a $200 book, or drive to the public library a dozen times (which is what did).And second, city inspectors should be smarter about their field than I am ! ! ! During this project I've had a half dozen inspectors out here, and three of the six were bright as a burned out bulb. I had a HUGE fight with the framing/structural inspector. Finally his supervisor came out and confirmed that I was right and the putz inspector was wrong.

author: scrat
author_rank: Frequent Contributor
timestamp: November 03, 2010, 05:07:32 pm
content: Quote from: JohnS_AZ on November 03, 2010, 03:03:01 pmYes, it's the same, in my poor technical English. I supposed it was the good term, but didn't verify. Our popular term is "salva-vita", which means "life-saver", while technically they're called "interruttore differenziale" ("differential breaker"), because of their differential sensing action.They are required on every system, following the principal breaker, and for civil systems the Delta current is 30mA. This really saves life in most of the cases.I'd ask two questions, if possible...How is the neutral wire connected to earth in your country? Here it is connected only at the last transformer near the user: the 3-phase transformer central point is earthed.The second is maybe stupid: why did they decide to connect neutral to earth? If it was a completely isolated circuit, there won't be any problems if one touched the hot wire. That's indeed what they do in certain particular systems.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: November 03, 2010, 05:17:58 pm
content: Quote from: scrat on November 03, 2010, 05:07:32 pmSo that when you get a live to earth short it blows the fuse.You couldn't rely on it floating for safety, as a short between one side and ground would go unnoticed until someone touched the other one.In the UK, a centre-grounded 110V supply is common on building sites and some factories for additional safety.

author: JohnS_AZ
author_rank: Frequent Contributor
timestamp: November 03, 2010, 06:40:59 pm
content: Here, the power comes to the house, through the electric meter, and then the service disconnect (a 2-pole 400A breaker). The neutral is grounded right there through a 6' copper grounding rod. Both neutral and ground continue to the distribution panel (the one I replaced) where the hot leads go through a 200A main breaker, the ground buss bar is on one side of the cabinet, and the neutral buss bar is on the other.Connect them together, or mingle the neutrals and grounds across both bars and you'll fail your inspection in a heart beat.

author: PetrosA
author_rank: Frequent Contributor
timestamp: November 04, 2010, 01:55:19 am
content: John summed it up pretty well. The ground and neutral (together with a ground rod, structural steel and water pipes) are only allowed to be bonded together once in the building wiring system, at the first (main) disconnect of a service. If the neutral and ground were to be connected at any point after the main service panel the ground wire would carry a portion of the neutral current - not a desirable thing.Like Mikeselectricstuff said, grounds aren't allowed to float because that would be a hazard in any system that isn't highly maintained and monitored. They do use a floating ground in some hospital operating rooms (I think to prevent sparks igniting oxygen) but I don't know enough about that to say more.A differential breaker is the same as a GFI (US) and RCD (UK) with the main difference being that in the US, we use a Delta current of 5mA instead of 30mA. Generally, the trend here in the US has been to use GFI devices instead of breakers. They are cheaper and it's more convenient to reset a receptacle where it trips than to walk through a building and find a breaker. Price for GFI breakers varies greatly depending on brand, number of poles and current rating. A common residential single pole breaker (15A or 20A) with GFI protection costs about $35-$90 while two-pole (120/240V) can cost from $150-$250. For a typical 200A service, there are usually 40 circuits, some single pole and some double. At the low end of those prices, you would be paying about $2400 for breakers, and the high end more than double that. Large "McMansion" style houses in my region have 400A services with two 200A panels, so the price for GFI protection would be astronomical. GFI mains would not work in the US as there are only single bus panels sold here and most people would not want the entire house to shut down for a ground fault.

author: EEVblog
author_rank: Unknown
timestamp: November 04, 2010, 02:26:48 am
content: Quote from: JohnS_AZ on November 03, 2010, 03:03:01 pmA "power point" is what we call the 240V mains outlet socket on the wall.I thought it was pretty much a universal term?The "differential breaker" is an ELCB or Earth Leakage Circuit Breaker here in Oz. They are mandatory on all new homes.Dave.

author: PetrosA
author_rank: Frequent Contributor
timestamp: November 04, 2010, 02:45:17 am
content: Quote from: EEVblog on November 04, 2010, 02:26:48 amNah, nothing universal about the names of electrical parts... Even here in the US terms vary from region to region and again in the code book. Here (commonly) a "socket" would be what you screw a light bulb into, an outlet is what you plug a cord into and Power Point is some nasty software from Microsoft. On the other hand, my grandparents' generation would have called an outlet a socket. An electrician would call an outlet a "receptacle". To make things more confusing, the code book defines "outlet" as any place the system wiring in a building is meant to be connected to "utilization equipment" IOW any box where a light (or luminaire), receptacle or appliance can be fitted permanently. Sheesh!

author: EEVblog
author_rank: Unknown
timestamp: November 04, 2010, 08:50:39 am
content: Quote from: PetrosA on November 04, 2010, 02:45:17 amMy head hurts, I need to go lie down!Dave.

author: scrat
author_rank: Frequent Contributor
timestamp: November 04, 2010, 10:12:34 am
content: Quote from: PetrosA on November 04, 2010, 01:55:19 amAs I imagined, the problem with floating neutral would be if it was connected at two points at the same time, while I didn't have considered the impossibility to monitor short to ground faults. Your explanations make it more clear to me now. Thanks.Now I'm wondering which is the best way to clamp neutral and ground: at the source (nearest mid-voltage to low-voltage transformer) or at the user? I found these schematics: which is the one used in your country?1)2)3)About house electrical systems... US situation is really another world with respect to Europe, and Italy in particular. Our typical maximum power for a house is 3kW (overloadable at 3.3kW for something like half an hour), which means about 13A at 230V!I can hear you laughing even from hereThis is mainly because of our little availability of energy (oil at the first place) and the fact a referendum in 1986 (just after Chernobyl accident) stopped all nuclear plants. These days it's going to be a luck, perhaps, even if in the past the high price of energy has braked so called "economical development", or consumption.

author: JohnS_AZ
author_rank: Frequent Contributor
timestamp: November 04, 2010, 03:51:56 pm
content: 3kW? Yikes!I just installed a new stove/oven in the new space. It's maximum power draw (I presume that means all elements on full blast) is 10.5 kW. I imagine the oven alone uses more than 3.

author: PetrosA
author_rank: Frequent Contributor
timestamp: November 04, 2010, 11:51:11 pm
content: Here we use drawing 1. Much of the US is not a village based infrastructure like in Europe, so houses may be too far from each other to run 120/240V feeds. Utilities normally run higher voltage primaries (above 1.2kV) and each customer will have their own dedicated transformer. There will be a ground rod at the transformer and another at the house. The utility will bond the neutral primary, the center tap and the ground rod together at the pole or ground mounted transformer and run three wires from there to the customer (two hots and a neutral). After the meter, those three wires are run to the main disconnect (may be integral with the main panel) and a ground rod, metal water pipes and structural steel are connected to the system. At this first disconnect panel, grounds and neutrals may be connected to the same bus bars. After this panel, grounds and neutrals must be kept separate so that no neutral current is carried through the grounding conductors which are only intended to provide an equipotential reference for hot to ground shorts. The ground rod is intended to provide a >25 Ohm path for high voltage (like lightning) in the event of large spikes.

author: scrat
author_rank: Frequent Contributor
timestamp: November 05, 2010, 12:36:45 am
content: From your description, US system seems much more to the third drawing than to the first, which is the one used in Italy. Here we can't connect neutral to earth after the transformer (which usually is 20kV to 400V 3-ph, meaning 230V each phase).

author: PetrosA
author_rank: Frequent Contributor
timestamp: November 05, 2010, 12:47:10 am
content: Ah yes, you are correct. I didn't notice that in the first drawing the neutral and ground are not connected. The fact that the first drawing has a grounding electrode at the panel and transformer makes it more like US systems (if you add the bonding between ground and neutral).

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: November 05, 2010, 09:36:52 am
content: 3kW? jeez....The standard electricity company fuse in the UK is 100A, i.e. 24kW

author: scrat
author_rank: Frequent Contributor
timestamp: November 05, 2010, 11:50:21 am
content: Quote from: JohnS_AZ on November 04, 2010, 03:51:56 pmQuote from: mikeselectricstuff on November 05, 2010, 09:36:52 amI can assure you that it is possible to live comfortably with 3kW, provided that you have a combustion heating system (methane is very popular here, but nowadays pellet and wood are increasing) and a gas kitchen!Almost all of us have many lamps, some computers, a fridge/freezer, a dishwasher, an oven and a (little!) air-conditioner. We just try not to use all of them at the same time!

author: PetrosA
author_rank: Frequent Contributor
timestamp: November 05, 2010, 12:21:22 pm
content: 3Kw sounds ridiculously small, but I can see how it would be enough in many cases. Many apartments in Europe are too small to fit enough equipment to use a whole lot more than that. It also would depend on whether it was 1 phase or 3 phases. Glancing at what's available to individuals and small businesses in Poland, the choices are as follows:Main breaker size: 6A | 10A | 16A | 20A | 25A | up to 63ASingle phase (kW): 1 | 2 | 3 | 4 | 5 | -Three phase (kW): 3 | 6 | 9 | 11 | 14 | 18/20/22/28/35I ran a coffee house (multiple coffee machines, dishwasher, hot water, heat, lighting, refrigeration on a 14kW three phase service with no problems ever.

author: scrat
author_rank: Frequent Contributor
timestamp: November 05, 2010, 01:56:57 pm
content: Quote from: PetrosA on November 05, 2010, 12:21:22 pmIt depends. As mike stated, not all Europe is in the same condition.Italy is one of the "worst" cases, since the lack of nuclear plants (and other political choices made in the past). But not all houses are that small, especially in the Po Valley (the North plain), where almost everyone runs his small company. It's just habits, like for cars: we usually drive cars with 1.2 to 1.6 litres motors, even if this may sound ridiculous for the US and, for example, Venezuela, where a Litre of gasoline costs few cents.Sometimes, having more only allows one to waste, and for electrical energy we simply couldn't do it.However, thermal power (heating, water and cooking) in our houses typically comes from gas (buthane or methane) or fuel oil. This isn't a little power source, since in my region (where winter temperatures can get to -20°C, even if in summer we reach 38°C), and it ends that a gas thermal unit for a house can easily be 15kW. They made a wide methane pipe net, so almost every house in Italy can have it relatively cheap.We are not that virtuous!

author: PetrosA
author_rank: Frequent Contributor
timestamp: November 06, 2010, 01:24:30 am
content: Quote from: scrat on November 05, 2010, 01:56:57 pmI understand completely. I lived in Poland for 14 years. Most apartments there only have a 3kW single phase service, but hot water, cooking, heating etc. is done with gas so it's not an issue. The largest loads for average people are a washing machine, coffee maker and toaster oven.I don't know for sure, but I suspect that most EU electric utilities also calculate loads slightly differently than we do here in the US. We tend to have enormous sized services, while in reality if you took readings in homes, most people are only using a small fraction of what their service could supply. That's the way we have to calculate loads in residential wiring - we pretty much have to assume an array of standard loads and that everything will be turned on at once. I think this style of calculating is connected with the fact that houses here are much more flammable that the homes in Europe and an overloaded electrical system can be very dangerous. Commercial services are more accurately based on what's installed, because you usually know exactly what a customer will use.

author: SkyFx
author_rank: Newbie
timestamp: November 12, 2010, 05:42:39 am
content: Hi there,its my first post here and i had some time left, so here is the situation in Germany:Switching, rewiring and maintaining electrical installations for voltages between extra low voltage range (max. 50V AC, 120V DC) up to "low-voltage nets" (max. 1kV AC, the translation doesn´t really work here, it includes the usual 230/400V house power feed) requires training, an exam and safety equipment if needed. For a house builder it may be OK to wire on his own and have some electrician check it, measure it and switch it on after inspection, but given the vast amount of standards and safety rules it would be a high risk to just tinker with it. E.g. measurement of ground wire resistance is a must and therefore a knowledge of the maximum values too. As i have learnt the job of an electrician all rules are made to come close to the targeted rate of 0% accidents and i´d say its quite good this way. Everyone has heard a story of a wrong wiring and artistic installations, so training and requirements have been evolved over time without being flipped over one day to another. The costs are higher than somewhere else this way, but its proven reliable and sat a base everyone can be sure it works as intended.Everyone may tinker with extra low voltage devices and nets, but when bringing them to the market it has to comply to several standards. Of course an engineering degree may entitle people to do the electrical work in their homes, but the mathematical safety is not exactly the same as the ones required by standards. Most people at least know that it can be dangerous and the practical side of things can become a no-go. As everywhere the right set of tools, implementation and knowledge is required.Usual there are TN-C-S nets as well as TT-C nets, so the star point is connected to earth (Terre) at power source, may be connected to earth at sink, there is a neutral wire (N) and a ground connection may be combined (C) with neutral or must be separated (S) when cross sectional area of ground wire is reduced under 10mm². Plumbing is mostly connected to a ground rod nearby the house, an FI (differential breaker) is required in bathrooms and TN-C-S nets, usual sized for 30mA. Medical equipment must afaik use an isolated net. A 20kV Transformer is located to power a whole street length of 200m (30 houses or so).Most areas use afaik a ring topology (so two errors needed to fully shut off an area), a star topology is mostly used in rural areas. Of course there are plenty reasons to do it different in commercial applications.Some years ago the industry made the market-typical claim that using less energy raised the price - as power plants tend to not run on optimum output. Also because "green" energy sources like wind and solar power may not deliver constant power but have to have a higher priority (the power they generate costs more to finance the spread of this technology). As well as there is constant discussion about deletion of nuclear energy. Seethisgraphic for which energy source feeds what magnitude of electrical power in a daily chart over here.Broad introduction of electric vehicles may change that picture quite a lot as well as more renewable/green energy sources. Some papers would use the car batteries as some sort of buffer, which would bring much more options into the power distribution and load curves, but also requires a stable and reliable net and adds a new load to the equations of a household.wbr,SkyFx

author: PetrosA
author_rank: Frequent Contributor
timestamp: November 12, 2010, 12:40:56 pm
content: Quote from: SkyFx on November 12, 2010, 05:42:39 amI have to admit that this is the one thing to do with wiring in Europe that I never really understood the rationale of. In the US, we use a standards system, i.e. for any given size wire there is a minimum size wire specified for use as a ground conductor. It is very easy to calculate a larger size for voltage drop if you have a long run as well. It seems it would be a waste of time to have to calculate this value for each and every installation.

author: SkyFx
author_rank: Newbie
timestamp: November 13, 2010, 05:36:17 pm
content: Its been a while for me to really do that stuff, so it may only play a big role for wiring inside of equipment with multiple power feeds and for checking equipment, as the standard cables have the same wire size anyway. Which means only fuse size and cable need to match to safely break the circuit in case of a wire touching a conducting case. So its standardized stuff anyway while purchase and installation.On the other hand measurement is the only way to validate this safety precaution will work. It is not the wire sizes alone, it includes the statement that every single contact the ground wire takes does give a good connection.wbr,SkyFx

author: Unknown
author_rank: Unknown
timestamp: November 14, 2010, 07:25:51 am
content: Quote from: EEVblogIn Aus you cannot! A sparkie signing off on your work is actually in breach and would be liable if anything went pear shaped. No qualified person can only work under constant supervision of a licensed tradesman.Quote from: EEVblogIt is nuts and its getting worse to the point of stupidity. Somewhere in some drawer I still hold a NSW electrical license, getting one now would require an annual fee to keep it. But despite being qualified I cannot do electrical work with that license anywhere but art my own premises. You have to pay another tax in the form of an electrical contractors licence before you do work.Basically any fixed wiring in AU must be done by a licensed tradesman.But wait there's more, our nanny state governments have entrusted AMCA with all things data and communications,and those muppets take bureaucracy to a new extreme. To do something as life threatening as punching down a few Cat5 cables or having your electrician conceal your speaker wires is also illegal unless you/they hold a cabler's licence. To get a cabler's licence involves a period of time inversely proportional to the fee paid. So the vandal in the cabover van is legally qualified to run data cable in your home yet the electrician who spent four years training or you with an engineering degree cannot.It's absolute madness in comparison to the way things are run in NZ or the USA. Quote from: EEVblog on November 03, 2010, 10:35:01 amBe careful here too there is some absolute garbage being sold, and it's all fully approved. A reasonable name brand circuit breaker sells retail for about $25. You can buy a fully approved knock off for around $2. Same for power outlets but I'd want my insurance paid right up before plugging a heater or air conditioner into one. A quick inspection will show the difference to anyone with a pulse and a clue, and yet the people who insist on all the licensing have approved the garbage.Quote from: EEVblogActually you can. Anything on a plug and socket can be done legally by handyman/others. Just don't try it on a union site.You can wire up 100A of three phase cable but cannot change a GPO (power point) in Australia.Tried to buy a piggy black plug lately? You cant, they've been deemed illegal, you can only buy one as a fully moulded lead. Why? Because some knob and candidate for a Darwin award decided to wire one up as a cord extension socket and turned out all the lights including his own on those 3 bonus brass pin on the back of his creation.Quick hint: GPO is a power point but GPO being the trade name, you pay a lot more at the electrical wholesaler if you ask for power points.

author: Neilm
author_rank: Super Contributor
timestamp: November 14, 2010, 08:46:06 pm
content: Quote from: EEVblog on November 03, 2010, 05:08:30 amDave - I know the feeling. I had a conservatory added a few years back. I had to get an electrician in to wire it up and we got talking on this subject. He was telling me how important it was, how they had to do safety tests with specialist equipment and the like. I pointed out that the tester he was using was made my the company I work for. I also pointed out I had just done an improvement to it and was a member of the committee that examined the things and agreed that they were safe for sale.YoursNeil