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14th Jan 2019, 09:05 PM #31
There is an approval process for the sale of electrical articles. Electrical items fall into either 'Declared' or 'non-declared' categories. Welders can fall into either of these two categories-
A single phase machine with a 100% duty cycle of <65A is a Declared item.
If a machine is 'an arc welding machine promoted exclusively to industry', then it becomes a non-declared item.
Declared need to be independently tested. Non declared may be tested, but need to meet at minimum AS3820:2009 -Essential safety requirements for low voltage electrical equipment.
Part of the approval process is that the machine is certified 'as tested', so if you sell a machine other than how the testing organisation viewed it, it's no longer compliant, and you go thru it all again.
Let's just say I work in sales for a company that (among many other things) sells welders. My daily job exposes me to many people who sometimes have little understanding of what can go wrong if these types of machines are not treated with a bit of respect, and there is a strong education piece around this.
I am not an electrician. I am tertiary trained in science and business, smart enough to know more than I probably should about many things, and dumb enough to keep learning it.
For the 15A GPO on a general power circuit- I've not undertaken this work myself, but have heard of sparkies going either way with the install. Some might see it as a low risk, whack it on and make it a gravy job, others give it a bit more thought and academic rigor. In the end of the day, their job and their licence is on the line.
As for the latter question- I'm sure we're on the same page here, maybe my delivery was off...
I think my original point is that there are multiple engineering controls (heirarchy of controls, if you are the HSE/OHS type) that act in layers to prevent 'bad things' happening.
For Electrical installations, the device has to be fitted with a plug based on what sort of load it could put on the circuit. As such, the electrican installs an outlet / GPO to suit this plug, but also ensures that the cabling is specced accordingly, like you said, Voltage drop, resistance, etc. On top of this all, the circuit breaker is the weak point in the whole scenario. Likewise, when a business has their equipment test and tagged, equipment can be tagged out if not compliant, or passed if deemed safe.
When an individual starts deconstructing these layers of control, the likelihood of a problem eventuating in normal use increases. Particularly so when we are talking not about a 16A load on a 15A rated circuit, but operating at 2-3 times the design of the circuit, say a 250+Amp welder with an effective current of >28A on a 10A circuit (trust me, I've seen it). In these cases, small problems quickly become larger ones if one piece of the system is not up to scratch. It may be a problem, or it may not. But the consequences can be significant, hence put faith in the trades, the standard, and the certification behind it all.
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14th Jan 2019, 09:21 PM #32Pink 10EE owner
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14th Jan 2019, 09:41 PM #33Most Valued Member
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Very interesting. So can we assume that a machine greater than 65A @100% is deemed to be marketed exclusively to industry and thus "non declared" for the purposes of certification? That would mean that a very large number of machines, if not the vast majority would fit into that category.
Your example of the 250A welder drawing 28+ Amps is very accurate and one that I have personal experience of. As I mentioned a previous workplace had a second shed wired in. In that shed we ran a 270A single phase mig. Do you know what the sparky fitted to run the machine from? A 10A GPO fed from a C curve breaker. Obviously not all sparkies are created equal.
I strongly suspect that more 15A gear has the earth pin ground down or is run from converter leads than is ever plugged into 15A GPO's to be honest. I understand the rules and the reasoning, but realistically it just doesn't happen that way. It also seems that many sparkies do not exactly work to code either.
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14th Jan 2019, 09:41 PM #34Member
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A bit off topic, but I have just gone the other extreme when I got 3 phase connected... to keep my options open I said make the sub-board in the shed good for 50kW. The cable to the shed is as thick as my thumb!
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14th Jan 2019, 09:44 PM #35Senior Member
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Could you please provide a reference for this oft-quoted statement? My copy of AS/NZ 3018-2001 'Electrical Installations - Domestic Installations' has on p62 a Table 6-1 "Guidance on the number of points per final subcircuit" which clearly sets out the circuit conditions for one, two, or three 15A socket outlets per circuit. For a common 2.5mm2 wired circuit protected by a 20A circuit breaker, two 15A outlets are allowed except when the wiring is completely surrounded by thermal insulation -Item(I). Three 15A outlets are permitted on a 25A circuit with the wire gauge dependant on the installation method used.
Chas.
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14th Jan 2019, 10:51 PM #36Member: Blue and white apron brigade
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14th Jan 2019, 11:56 PM #37Golden Member
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The NZ argument is certainly not a straw man and I am surprised with your interest in electrical safety you are not already aware of the meticulous statistics kept by the Electrical Regulatory Authorities Council?
You can find the latest at http://www.erac.gov.au/images/downlo...02017-2018.pdf
For the last few years NZ has certainly had less deaths people per capita by reason of electrocution see Graphs 1.2 and 1.6 of the above document. To say "it's a safer proposition to have it within the scope of a professional" is clearly difficult to justify when the data collected by the regulatory authorities indicates otherwise. Perhaps if we had more decisions based on evidence we might see even better outcomes?
I for one would have liked the opportunity to tighten those two screws (left loose by two separate electricians) that left two circuits smouldering away in at my place. One in the shed and one in the house. Two separate certificates of compliance provided to me meant nothing, the work was dangerous. Who ever devised a system where you certify your own work?
Back to the hypothetical. I am lucky I didn't end up with Richard on skid row due to depression brought on by a system that allowed a pair of dullards to risk the lives of my family and myself whilst a safer system that would have avoided that outcome operates only a short flight away.Last edited by lamestllama; 15th Jan 2019 at 12:00 AM. Reason: clarification
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15th Jan 2019, 08:40 AM #38Most Valued Member
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It would certainly seem that you have a point. Even when taking into account the much smaller population of New Zealand, they still come out ahead. Looking at table 4. Fatal Electrical Accidents since 2000, the tally for Australia is 314 fatalaties for the period 2000-2018, while New Zealand registers 56. Let us assume that New Zealand has a population 1/5th that of Australia, so that would adjust the figures to 314 and 280 respectively. Still a clear advantage to the Kiwi's.
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15th Jan 2019, 08:41 AM #39Most Valued Member
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15th Jan 2019, 09:05 AM #40Golden Member
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Graph 1.6 does the work for you it is per capita so it takes into account the differences in population. Not only does NZ have a lower electrocution rate but if you look at the slope of the linear regression lines you can see that NZ is reducing its rate of electrocutions at a faster rate than Australia.
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15th Jan 2019, 09:35 AM #41Golden Member
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15th Jan 2019, 10:08 AM #42Pink 10EE owner
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15th Jan 2019, 12:44 PM #43Member: Blue and white apron brigade
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Slightly off topic by I occasionally wonder about a bunch of things related to electricity like how utterly clueless most people are about the dangers of electricity compared even dare I say it to motor vehicles, and why machines are not fitted with simple $2 ammeters.
Users of motor vehicles require require some training yet very little little is provided regards electrical safety training for the general public or for that matter even in the workplace. Instead we "nanny state" it and try and make everything as protected as possible. Vehicles will probably only every get to that level when they are driverless.
I taught 7 year of High school physics and the fact that only a few % of students do this subject to even a basic depth is just one of many problems. The other thing to remember is it is possible to "pass" high school physics, but completely fail the section on electricity.
Then I taught basic and advanced physics and electricity subjects at Uni for ~25 years and what I saw was the knowledge that students came in with was woeful to say the least and not much better when they graduated. I regularly conducted pre and post test using simple DC circuits ie globes and batteries and how much current is needed to kill some one. I have to say the results were very depressing. Even students that arrived with electrical and related trade certificates, some upgrading their qualifications to engineering degrees, had a very limited fundamental understanding of electricity. The most unusual students I taught were two 30 something ex-SAS specialists starting their engineering degrees. They had extensive training and field field in electrical circuits related to explosive devices but had a surprisingly poor understanding of electricity itself.
During my time at Uni I participated (ie I was a subject or participant) in a research project conducted by a PhD student on the depth of knowledge and understanding about electricity form primary school age through to fully experienced electrical engineers and how these people were taught about electricity. School and uni curricula were assessed in terms of the time spent and the way students were taught. The results were unsurprising, electricity occupies a very small portion of basic science curricula and like almost all subjects student were taught using only "models and algorithms" and students stick to these like glue when they should be moving up the ladder of fundamental understanding and we leave it to the students to make the leap to deep understanding and generalised cases. Often the exams might test generalised cases usually without teaching the students about it, and naturally this is where students generally poorest poorest at.
My experience in dealing with sparkies has been mixed. Some of them are fantastic - the 80 year old sparky at our mens shed is great, thorough, careful, and from the "sneaky" questions I ask him he really knows what he's doing. Some, I cannot for the life of me understand how they ever got a cert. Most sparkies (like most people) operate at what is called an "algorithmic" or "procedural" level because this how they are taught. EG Here are the steps to solve this problem - don't worry about understanding them, just remember them. These procedures are usually designed to keep them and the public as safe as possible. However, to cope with as many eventualities as possible, eventually all procedures/regulations/installation standards become complex, unwieldy and harder to remember and unfortunately simply cannot cover all possible situations. Unless a person has a deeper fundamental knowledge of the topic they may then get it wrong.
I reckon one of the main reasons for this is that less and less time is allocated to studying anything at tafe/uni and in particular hands on (lab/prac) time has been cut by the bean counters by about half.
As people get more and more life experience and life practice they will come across more cases and build their experience and knowledge base up but this is neither a fast or safe way to learn. An extreme case is bomb disposal where the ground rules can change on a daily basis and they have limited ways of learning other than by example and is why they have such high death rates.
So my ramble brings me back to where I started and that is electricity should be more prominent in school science and we should encourage more students to study electricity in general to a greater level and there should be more public education about about it. The odd ad on TV about staying away from fallen power lines is useful, but woefully inadequate.
Now lets get to the $2 ammeter.
It's mandatory that vehicles have speedometers so users should know how fast they are going and what limits to stick to but it's very rare to see a simple V/I indicator device fitted to an electrical appliance. I contend especially larger machinery should have a V/I meter fitted within easy operator view and a blurb in the manual to explain how to use the meter in relation to usage. Even the fact that is says what the V/I is at any given time would help users better appreciate what is a low current/load and what is a high current/load and the 240V is NOT always 240V etc.
I have an ammeter on all my 4HP machines, WW BS, compressor and Dust collector while for other machines and tools I have a short extension cord with a VI meter in the middle and find and find it really useful. Experienced users who already have a feel for machinery would not need it but I reckon newbies especially could benefit greatly while they get the feel of the machinery. One some machines running on VFD I sometimes monitor the current that way but usually the single line display is left on frequency which is where dual line display VFDs come in handy
On simpler/simpler appliances it does not even have to be a meter - it could be an indicator light like on a dash - thing goes orange or red - think about what this means. It could be your blades are blunt or you have another extra load. We're'e starting to see these load indicators on power tool batteries - why not have them for the tool itself
Instead of doing something useful like this we have fridges connected to the internet that tell you when to order more food - how arsed about its this?
Yes, initially the meters and indicators could create a some initial confusion but there would also be many useful learning opportunities come out of it.
Ramble over.
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15th Jan 2019, 01:50 PM #44Golden Member
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BobL I agree with your thoughts on "procedural or algorithmic" knowledge. In nearly every arena we see people taught to pass a test rather than taught to understand the fundamentals and thus have the basis for solving problems outside the scope of their teaching.
In particular regard to electricity I would say the nanny state approach in this country means that electricity may as well be magic for most people. They have no sense of anything to do with the subject because they are largely legislated away from getting any exposure. In NZ the government actually supplies the public information on how to DIY the electrical jobs they are permitted to perform themselves. I believe this increases the awareness of the dangers associated with electricity and lifts the awareness of society as a whole.
The $2 ammeter is probably the old fashioned solution now. It wouldn't be difficult to program a IOT device or bluetooth device to monitor your power usage keep statistics and report any anomalies audibly, visually or otherwise. Perhaps there is a market for such a device?
In respect to the fridge being connected to the internet is is just an example of the way the IOT will if we participate make us the product.
Eric
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15th Jan 2019, 02:49 PM #45Most Valued Member
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I wholeheartedly agree with your comments BobL. Everything is becoming dumbed down. Even when you buy consumer electrical gear they now come with an instruction book and a quick start guide. Most only read the quick start guide and as soon they get lights or noise they are content. We only want to learn what we see as enough.
I believe that we have created the dumbest generation ever. Why? Because there is unprecedented access to information via the internet yet the most common searches relate to , celebrities or game hacks. If we go back a few years, people knew why and how an engine ran, they knew about mechanical advantage and leverage, some actually had reasonable knowledge of electricity. Now even trades are dumbed down and knowledge is being lost. If we compare our path to that of Europeans or Asian nations, it is not hard to see why we are being left behind.
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