Author Topic: AH#14 - Electrical Work  (Read 11777 times)

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Offline SkyFx

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Re: AH#14 - Electrical Work
« Reply #25 on: November 12, 2010, 04:42:39 pm »
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. See this graphic 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
 

Offline PetrosA

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Re: AH#14 - Electrical Work
« Reply #26 on: November 12, 2010, 11:40:56 pm »
E.g. measurement of ground wire resistance is a must and therefore a knowledge of the maximum values too.

I 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.
I miss my home I miss my porch, porch
 

Offline SkyFx

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Re: AH#14 - Electrical Work
« Reply #27 on: November 14, 2010, 04:36:17 am »
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
 

Uncle Vernon

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Re: AH#14 - Electrical Work
« Reply #28 on: November 14, 2010, 06:25:51 pm »
Quote from: EEVblog
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.

In 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: EEVblog
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.

It 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. [/rant]   


Does anyone actually pay attention to the Aus rules Dave? Can you easily buy sockets, distribution boards etc. over the counter?

Yes, 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 etc

Dave.


Be 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: EEVblog
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.

Actually 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.
 

Offline Neilm

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Re: AH#14 - Electrical Work
« Reply #29 on: November 15, 2010, 07:46:06 am »

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 - 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.

Yours

Neil
Two things are infinite: the universe and human stupidity; and I'm not sure about the the universe. - Albert Einstein
 


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