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Sorry for bringing some realism into the panic ...
Voltage loss (hence power dissipation) through a cable is given as dU = (2 * I * l * rho) / A, where I is the current, l is the cable length, rho is a material constant which for copper is 0,0175 Ohm * A/m. A is the cross section of the conductor.
Filling in for I = 2 Amp, l = 4 meter, and A = 4 sqmm gives a voltage loss of (2 * 2A * 4meters * 0.0175 ohm*sqmm/m/) / 4sqmm = 0.07 V, through the maximum spine length in my house.
If, at the very end of a spine, I make ma maximum length rim, using 2.5 sqmm cables, the voltage loss is (2 * 2A * 4meters * 0.0175 ohm*sqmm/m/) / 2.5sqmm, or an additional 0.112 V, for at total voltage loss of 0.182 V. So with a 2A load, I will experience approximately 1.5% voltage loss along the cable. Given the 2A current - about 24 W - more than a third of a watt may be dissipated from my eight meters of cables. Alarm! Look out - Danger! Fire hazard imminent!
Most consumer points do not run from the very end of the spine, and do not have four meter ribs running from the spine. This 4 + 4 meters is an extreme worst case. For most situations, both cable lengths and currents will be (way) lower.
I can understand that there may be people who do not understand the need for power cables to dissipate a third of a watt over eight meters, thereby causing fires. Yet, others may prepare for it, and lay the cables to provide the necessary cooling for effects at this level.
BTW: Norwegian mountain cabins, far away from any 230VAC supply, have for decades had solar panels with battery banks providing 12VDC for light, small fridges, ventilation and other purposes, without converting the 12VDC battery power to 230VAC, but using the 12VDC directly. It would make no sense converting it to 2230VAC only to plug in a 230VAC-to-12VDC to get it back to the power required to drive the light and the cabin style cool box.
(Note to the OP, James Curran: Here you see the kind of arguments you must be prepared for if you decide to go for a low-voltage installation in your house!)
You didn't said 2A before. You said "almost 200W" which gives 10A.
The specification of the setup should be as detailed as possible. Which was my point in the misplaced last paragraph (I managed to track down the other post and pasted that paragraph at the bottom of this post).
It would make no sense converting it to 2230VAC only to plug in a 230VAC-to-12VDC to get it back to the power required
I agree. And I think modern houses should be built with a DC distribution network besides the AC one, given the increased proliferation of low power DC devices. This way, that network would already be certified for use since houses are inspected before being granted permission for habitability. Until this happens we should stick to what our local law allows.
I also think houses should be built with a network for internet where one can connect either an Ethernet cable or have small fixed converters to Wifi with smaller range and end this signal fight where a single router must fight with its 200 neighbors. But that is a conversation for another topic.
I know my English is not the best and my explanation capabilities are bad, as I am not used to speak to people, but I am trying to help (and apparently failing). You seem more qualified than I so I will just stop trying.
Best of luck with your setup James.
In my previous post that says
"DC distribution only makes sense for very high voltages (over 100KV) since losses in AC, at those voltages, become higher."
should have said
"If you really think you need a DC distribution system make sure your specifications of what (with corresponding voltages and maximum currents) connects where (how far from the source) is well defined. Then either hire a professional that does DC installations or ask someone with knowledge to validate your setup before starting to build it, preferably someone with knowledge about your local laws."
You didn't said 2A before. You said "almost 200W" which gives 10A.
True - you were the one setting the limit for 4 sqmm cable at 2A. So I made the calculation of heat loss for what you consider the maximum handling capacity of a 4 sqmm cable. You can easily repeat the calculation for 10A - in fact, the voltage loss is proportional to the current, so for the 4 m of 4 sqmm cable, the loss is 0.35V, and for the 4 m of 2.5 sqmm cable 0.56V.
However, we are here talking about extreme worst case examples. In my house, no 12V equipment lies at the end of a 4+4 m cable stretch; the typical is half of that. Furthermore: No single branch will carry 10A (or even close). As I wrote in an earlier posting: You will of course protect every single branch with fuses dimensioned for the expected load on that branch. -- That is even if the cable dimension would allow for a higher current than your expected load. If you cause a shortcut, the fuse should blow, rather than the cable overheat. This is part of knowing how to do it.
ask someone with knowledge to validate your setup before starting to build it, preferably someone with knowledge about your local laws
Our Norwegian laws set a limit on the total effect of you 12VDC network at 200 W, and you must stay below 50V. Cabling must be available for inspection everywhere; if they go through walls or ceilings, they must run in metal pipes (in principle: Non-burnable material, but for all practical purposes, that is metal). I am replacing cornice with similar-looking cable gates with fronts that can be flipped off to get at the cables. (Side remark: The cabled Ethernet runs in the same cable channels.)
12VDC networks have a long tradition in faraway mountain cabins in Norway, and we have a multitude of shops selling all sorts of parts for setting it up: Cabling, fuse boxes, water pumps, plugs and sockets, lead-acid batteries and solar panels. You can buy all sorts of lamps, fans etc. made for 12VDC, intended for cabin use. We just don't use it much in regular homes. It is easy to find people with a good understanding of what you can and should do, and what you shouldn't, and the common knowledge level is high. We know because we need to know. We have two big Norwegian language websites, named ByggeBolig.no (like BuildingAHome) and ByggeHytte.no (like BuildingACabin). In both forums, various issues related to low voltage power is regularly brought up. Although the majority of posters are DIY guys, several professional craftsmen, including electricians, are active and provide professional advice.
Ah Ok, don't take my mains. Another issue is the grounding of things often cheaper USB devices use a common ground to the supply to make things easier and cheaper to make. Be careful when using these things as you can get a tingle, which ca,n if things go south, result in mains being applied. While it is a good idea to some extented (Low Volts, Low Amps) the legislation needs to be much tighter. It is the wild west with some products (the company I worked for ordered all office staff USB fans, I did a test and found the earthing/grounding issue told them, they were not happy!)
Before we reinvented ideograms (a.k.a. emojis), it wasn't uncommon to hear people argue that our Western style of writing, representing concepts or ideas by 'word' symbols bearing no resemblance to any appearance of the concept/idea, is more 'sophisticated', as is is more 'abstract'. Ideogram based written languages are more 'primitive', as they do not represent the idea, only the 'thing'...
I don't think any linguist, by profession, would support anything like that, but I have heard quite a few amateurs with a mental need to fiercely defend their own culture / language argue that way. (You wouldn't believe the arguments native English speakers can bring forth to 'prove' that English, according to any measure, is a much better language than not only Far East ideogram based ones, but also any other Western language!)
Western culture (although some parts of it more than others) see Far East culture (although some parts of it more than others) as a serious threat, and use any opportunity to stigmatize and condemn it, blame it for everything evil, and to fight it. If we had still been holding text and word symbols in high esteem, I am convinced that we, in the political situation of today, would have been ridiculing major Far Eastern written languages for being so primitive that they need to draw pictures of what they want to communicate.
We lost that opportunity by introducing emojis into our own written language. There is a major difference, though: In ideogram languages with a history of several thousand years, the ideograms have been firmly established with quite exact meanings (or well understood ambiguities - but that is no different from our word symbols!). Our emojis are still at the cradle level: We have only a vague idea about how to shape each ideogram. Most people can only vaguely explain the use of a given ideogram: They can tell what it shows (as an image), but not the interpretation of it in various contexts.
Note that this occurs at a stage where a significant fraction of the population already has lost contact with the word symbols. If you ask for a word representation of the same emotions as the emoticons, they are at loss. So they neither can express themselves in the 'old' written language, nor in an ideogram language that is well defined and equally understood by different readers. So the writer must bark louder, repeating six or eight bark emoticons rather than a single one, to make sure the message gets through. Communicating by decibel levels, that is where we are at.
Maybe word symbols are better, after all. Not better than ideograms refines through thousand years, but better than emoticons.
Emojis were (re)invented as part of alphabetical languages when people stopped trying to use words in their proper context. This was either out of laziness or because in many cases their vocabulary had shrunk to such a level that they were incapable of using language correctly. They are not a sign of advancement, but of regression of language skills.
Alphabetical languages have no intrinsic advantage over ideogrammatic languages as communication methods - as long as ideograms are invented in a timely manner to describe new concepts. It is not necessarily easier to guess the meaning of an unfamiliar complex word in an alphabetical language that it is to guess the meaning of a complex ideogram - all that is required is language-specific knowledge of how words (or ideograms) are formed.
One way in which alphabetical languages are superior to ideogrammatic languages is the ease of learning. Any properly-taught first grader who has learnt his/her language's alphabet can read a newspaper meant for adults and at least attempt to pronounce the words, even if he/she does not understand them all. Try the same experiment with a Japanese, Chinese, or Korean schoolchild!
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One experience coming a surprise to me: To a few of my native English speaking friends, the famous English is tough stuff[^] caused no problems whatsoever. They could read it out loud without stumbling, at the first try.
For both of them (all others had problems!), it turned out that they had gone to schools teaching words before teaching letters, learning words as integral units, to be understood in a context. Breaking the words into separate syllables and sounds, relating them to the individual letters, came much later.
These people had also, as kids, learned various conjugations and relationships to then roots of the words. So they could relate terms they knew to words they didn't yet know, but by structure, form or sound.
When you state "One way in which alphabetical languages are superior to ideogrammatic languages is the ease of learning", I am thinking: Yes. but in a very superficial way. When you teach a programming apprentice, you must teach him the difference between 0 and 1, between true and false (in the logical sense, not the moral one). And then: What now?
So you learn the bits and bytes/letters. Fair enough. But no wise man's knowledge has been limited to his familiarity with ASCII encoding. At which point on the ladder of enlightenment is that alphabet understanding that you strive for?
If a Far-East child must learn five thousand concepts/ideas (/ideographs) to read a newspaper, but here, in Western communities, you conclude that learning 26 character symbols is good enough to read and comprehend a similar newspaper...
Of course not! Any reader knowing only the bit or byte encodings, but haven't learned the semantics of the higher level symbols cannot make use of them for a higher understanding. In our culture, understanding characters as a basic block for the way we represent information, as words, but characters combined into words is not the only possible way of representing it.
I have a friend from China that's a professor in microbiology.
She cannot read a thesis in her own subject if it would be written in Chinese.
Whenever she encounters a new logogram that she has never seen before, there is no easy way to know what it means. Nor does she have a clue how it's pronounced.
That is certainly no different from word based languages!
I frequently encounter word symbols completely unknown to me. Often, I have no clue how the term is pronounced (read out loud English is tough stuff[^] if you don't get my point!).
In the academic, English-speaking society, you are expected to master a huge vocabulary of several ten thousands of words - or, if you like: word symbols. If you master several ten thousands of ideogram symbols, you will probably be able to get far in your professional field, regardless of culture.
I can easily imagine Chinese propagandists ridiculing Westeners for not knowing the meaning and/or pronounciation of some professional term. You have to learn the terminology to read it. There is no principal difference between character/word based terminology or ideogram based terminology.
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In my youth, popular music was ridiculed for these primitivistic 'love, love, love' repetitions.
Maybe Norwegian culture was early in pointing out that endless repetitions of 'Glory, glory, glory' or 'Holy, holy, holy' (and several other mantras) were fully recognized in numerous musical works touted as Elevated Cultural Expressions.
I seriously suspect that in essential parts of Western Culture, even today it would be inappropriate to draw parallels between 'love, love, love' and 'Glory, glory, glory'.