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  1. #1
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    Default General lighting query

    I'm shopping for some gear while waiting for a sparky to decide to come around and I am a tad confused about the circuits and the rules.
    I need to buy a couple of angled battens, a floodlight and a new switch or two, if the battens have an earth terminal why don't the switches?
    Looking at a Clipsal WS226 that is left-over and wondering if it can be used so I don't need to buy another water resistant switch.
    We already have an external power point and I want the cheap floodlight to run from the same point
    I totally understand why a circuit always has to have the same gauge wire but if I'm getting him [ or her] to wire in a floodlight which only has a 2-wire connection why does it need 2P&E cable?
    What's the purpose of a floating earth wire?
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    We already have an external power point and I want the cheap floodlight to run from the same point...

    That's always an option but if you do that you'll lose a GPO plug in position.
    If you are saying that you are going to get them wired on the same circuit, then that's a no-no. Check your meterbox and you'll find 2 circuits (or more) one Light and one Power.
    And.....your point is.....what exactly?

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    I am not an electrician and I have not kept up with current requirements but I will try to explain what I understand the requirements are. An electrician will no doubt correct me if I am wrong.


    Firstly you can connect the floodlight to the circuit you have but, as you say, it has to be wired with the same gauge (or larger) than that used in that circuit. Earthing: It is an Australian requirement that lighting points (battens) have to have an Earth connection whether or not the actual light fitting requires an Earth connection. In the future the light fitting may be changed and if an Earth is required by the new light fitting then pre-wiring will simplify the change over. Some countries require an Earth connection at the switch and others don't. The UK does require an Earth at the switch and, at least at the moment, Australia does not. It is just a matter of each countries wiring rules.
    Technically if a circuit is extended then voltage drop and fault current needs to be considered but they rarely prohibit a domestic circuit modification.
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    OK That explanation makes sense, I'll get them to wire in a surface plug then and buy a light with a plug on it and spend the extra $10- if he'll mount a surface plug there, a well protected area but it is outside.
    The cheap floodlights are weatherproof, I'll see what he says but it seems a waste not to use the fitting and switch we removed when we started doing the cladding a few years ago
    @David E, well so far there are only two GPOs on this particular power circuit; it's a dedicated outdoor circuit with safety switch/ELB etc.
    Not much voltage drop over 4 metres of cable either as the sub-board is right on the other side of the first GPO
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    Quote Originally Posted by David.Elliott View Post
    We already have an external power point and I want the cheap floodlight to run from the same point...

    That's always an option but if you do that you'll lose a GPO plug in position.
    If you are saying that you are going to get them wired on the same circuit, then that's a no-no. Check your meterbox and you'll find 2 circuits (or more) one Light and one Power.
    I thought a light could be added to a GPO circuit but the light has to be connected with the same gauge wire as the ppt ie 2.5mm 2C+E, and the circuit at the box had to be marked as a mixed circuit.
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    Quote Originally Posted by Moondog55 View Post
    Not much voltage drop over 4 metres of cable either as the sub-board is right on the other side of the first GPO
    Here are some good calculators so you can see what the drops will be, just for reference.

    https://www.jcalc.net/voltage-drop-calculator-as3008

    https://www.jcalc.net/cable-sizing-calculator-as3008
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    Quote Originally Posted by METRIX View Post
    I thought a light could be added to a GPO circuit but the light has to be connected with the same gauge wire as the ppt ie 2.5mm 2C+E, and the circuit at the box had to be marked as a mixed circuit.
    Correct

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    Quote Originally Posted by Moondog55 View Post
    if the battens have an earth terminal why don't the switches?
    If a plastic "Batten Holder" does have a terminal connection for an Earth, it is only for a place to "park" the required conductors concerned until such time as they may be needed to Earth a replacement (Metal) fitting.
    The lack of an "Earthing Point" on Australian switches is because of a piece of (re)design of "switches" in Australia (and the UK), which now have no metal "ÿoke" which would need an "earth" terminal - nor have they anywhere where such a connection could be made. ("Switches" in North America do have this problem but that is not so in Australia.)

    If there are two or more (Protective) Earth conductors located in association with any Switch, all that is necessary is to connect these together - by the use of a twin screw connector, such as https://www.sparkydirect.com.au/p/88...0-per-jar.html

    [Use a Twin Screw connector (!) - As the Irish might say "To be sure, to be sure."]
    Last edited by FrodoOne; 13th Mar 2021 at 01:14 AM. Reason: uired

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    Quote Originally Posted by FrodoOne View Post
    If a plastic "Batten Holder" does have a terminal connection for an Earth, it is only for a place to "park" the required conductors concerned until such time as they may be needed to Earth a replacement (Metal) fitting.
    The lack of an "Earthing Point" on Australian switches is because of a piece of (re)design of "switches" in Australia (and the UK), which now have no metal "ÿoke" which would need an "earth" terminal - nor have they anywhere where such a connection could be made. ("Switches" in North America do have this problem but that is not so in Australia.)

    If there are two or more (Protective) Earth conductors located in association with any Switch, all that is necessary is to connect these together - by the use of a twin screw connector, such as https://www.sparkydirect.com.au/p/88...0-per-jar.html

    [Use a Twin Screw connector (!) - As the Irish might say "To be sure, to be sure."]
    So would this mean the AU switches are of superior construction to the North American ones ?, I notice the NA switches all seem to be be clumsy big things with massive screws located at the fronts of the switches, just like most stuff over there.

    Also I have always wondered why the earth connectors have two screws, and an open end on them, is this a carryover when earth wires were non insulated and was the wire was passed through the connector ?
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    Quote Originally Posted by METRIX View Post
    Also I have always wondered why the earth connectors have two screws
    I always thought two screws because it was the most important wire to maintain continuity, 2 screws to be sure!

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    Quote Originally Posted by phild01 View Post
    I always thought two screws because it was the most important wire to maintain continuity, 2 screws to be sure!
    Only on tunnel connectors, single screw for termination of electrical equipment eg lampholder, socket outlet etc

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    Quote Originally Posted by FrodoOne View Post
    If a plastic "Batten Holder" does have a terminal connection for an Earth, it is only for a place to "park" the required conductors concerned until such time as they may be needed to Earth a replacement (Metal) fitting.
    The lack of an "Earthing Point" on Australian switches is because of a piece of (re)design of "switches" in Australia (and the UK), which now have no metal "ÿoke" which would need an "earth" terminal - nor have they anywhere where such a connection could be made. ("Switches" in North America do have this problem but that is not so in Australia.)

    If there are two or more (Protective) Earth conductors located in association with any Switch, all that is necessary is to connect these together - by the use of a twin screw connector, such as https://www.sparkydirect.com.au/p/88...0-per-jar.html

    [Use a Twin Screw connector (!) - As the Irish might say "To be sure, to be sure."]
    I thought that the reason the earth was required at the switch was that power outlets and switches in the UK and Ireland are usually mounted on/in metal boxes fitted into the wall. This is to reduce the risk of fire due to a faulty connection and to trip, over current or leakage current safety devices in the event that a live wire disconnects and touches the earthed mounting box. The switch and power outlet mounting screws obviously screw into the box and are thus also earthed. I don't know what they do in the USA but from what I have seen they also use mounting boxes.
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    OK This explains some of the old switches and GPOs I took out of the old shed.
    Waterproof metal housings with very large earth wires and heavy brass screws and toothed washers on all of them.
    Never used them and they went to scrap, I assume my dad "rescued" all of them when wiring was renewed at the place he worked and was re-used to save a few dollars when he build the shed I pulled down.
    All connected by heavy galvanised steel tube too.
    Here's a question the Sparky couldn't answer, if it's legal to use a combined circuit why isn't there a "Combined" sticker in the set of red and green stickers you get with a board?
    EDIT
    When we bought the house there were two "combined " circuits, one for the shed and one for the sleepout but neither were labeled as such, actually the old board had very little information scribbled on it, just a pencil sketch on the wooden door that had faded with time and one of our biggest costs was upgrading the whole of house wiring when we need the aircons. So many hidden costs
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    Quote Originally Posted by METRIX View Post
    So would this mean the AU switches are of superior construction to the North American ones ?, I notice the NA switches all seem to be be clumsy big things with massive screws located at the fronts of the switches, just like most stuff over there.
    As to your question - my belief is definitely YES.
    While I fully agree with your comment, this opens up another "can of worms".

    You (and others) may be interested to view the advertising pictures of this typical North American switch and the associated videos.
    (https://www.homedepot.com/p/Leviton-...-100356976-_-N)
    (If the "explanation" in the first video concerning this SPDT switch as being a 3-Way Switch does not have you "tearing your hair" I will be quite surprised!)

    All of this could lead to a discussion, well away from the original topic, as to how Australian electrical equipment and practice differs from that in North America, the UK and Europe.

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    The switches are such clumsy looking.

    The three way explanation is a bit weird, but somewhat understandable.

    Our switch mechs can all be wired for three way (two switches to control one light) they have a C, 1 and 2 on the mechanism, a lot easier to understand than the video.
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    Quote Originally Posted by METRIX View Post
    The switches are such clumsy looking.

    The three way explication is a bit weird, but somewhat understandable.

    Our switch mechs can all be wired for three way (two switches to control one light) they have a C 1 and 2 on the mechanism, a lot easier to understand than the video.
    I agree with you, on all counts.

    In 2016 I was searching for information relating to switches (Mechs) when I came across this North American thread - where someone who was obviously in Australia had asked a question, three years previously.
    Largely because of the non-answers given, I posted what I believe was an appropriate response (even although the thread was by then 3 years old), for which I received two "Likes". (See https://www.diychatroom.com/threads/...switch.169515/)

    I have been following the questions on this site (and on the UK site of https://www.diynot.com/diy/) since that time and believe that I have learned a lot about North American and UK practices as a result.

    (I have also redirected several UK enquirers to the UK site.)

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    Quote Originally Posted by FrodoOne View Post
    The lack of an "Earthing Point" on Australian switches is because of a piece of (re)design of "switches" in Australia (and the UK), which now have no metal "ÿoke" which would need an "earth" terminal - nor have they anywhere where such a connection could be made. ("Switches" in North America do have this problem but that is not so in Australia.)
    I don't think that Moondog was referring to the switches themselves, but to the switch location. Nobody, I hope, would earth a switch. Metal switch mounting boxes and metal face plates are earthed.
    “What a fool believes, he sees. No wise man has the power to reason away”- The Doobie Brothers

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    Quote Originally Posted by FrodoOne View Post
    I have been following the questions on this site (and on the UK site of https://www.diynot.com/diy/) since that time and believe that I have learned a lot about North American and UK practices as a result.
    Come on don't keep us in suspense what's your opinion?

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    Quote Originally Posted by FrodoOne View Post
    I agree with you, on all counts.

    In 2016 I was searching for information relating to switches (Mechs) when I came across this North American thread - where someone who was obviously in Australia had asked a question, three years previously.
    Largely because of the non-answers given, I posted what I believe was an appropriate response (even although the thread was by then 3 years old), for which I received two "Likes". (See https://www.diychatroom.com/threads/...switch.169515/)

    I have been following the questions on this site (and on the UK site of https://www.diynot.com/diy/) since that time and believe that I have learned a lot about North American and UK practices as a result.

    (I have also redirected several UK enquirers to the UK site.)
    Here is a good document put out by Clipsal, it shows how the various configurations should be wired with the iconic range.
    Can't get any negative feedback of sharing this, as it's freely available on Clipsal's website.

    https://www.clipsal.com/getmedia/417...chure.pdf.aspx
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    Quote Originally Posted by Bros View Post
    Come on don't keep us in suspense what's your opinion?
    Of course, I am biased.

    However, I do know that in the 1930s certain persons in Australia took a (out of patent) US design for a Socket Outlet and improved upon it vastly.
    (The history of this is well covered in https://web.archive.org/web/20191019...plug/plug.html and seems to form the basis of the "history" referenced in https://www.plugsocketmuseum.nl/Australian1.html and https://en.wikipedia.org/wiki/AS/NZS_3112)

    What may not be well known is that at the same time Australia (virtually) "adopted" the North American standards for the "wall-plate", its fixing dimensions and the screws and the "threads" involved.
    This still applies and Australian wall outlets/switches will fit North American wall hardware and vice versa.

    (While in the 1970s Australia made the sensible decision to just rename screws etc. by approximate metric dimensions - but change nothing - strangely, the screws which held UK wall hardware to the wall boxes were changed to "metric" dimensions when the UK made their attempt at metrication, resulting in the obvious problems.)

    While Australia took the design for US switches at the same time (an example of which can be seen in Item #3 in https://www.plugsocketmuseum.nl/Australian2.html), after WWII the "Rocker Switch" mech which we all know today was developed - probably, by Clipsal.
    (This led me to couple the words "Schneider Electric Clipsal" in a search, which came up with this (https://www.youtube.com/watch?v=X91xou6SVVs), which touches but briefly on the Plug and Socket Outlet.)

    While Schneider Electric has some other "blurbs" relating to Clipsal, they have removed the Clipsal History page, which used to exist on the WWW.

    Interestingly, Schneider Electric has the following (https://www.se.com/id/en/product-range/62627-s-classic/?selected-node-id=12146085387#tabs-top), most of which fits a standard UK wall-box. Interestingly, it appears that the wall-plates are supplied with deeply recessed screws and "covers" for them, which accord with Australian practice.)
    (Unfortunately, it appears that one needs to put in https://www.se.com/id/en/product-ran...85387#tabs-top to their browser to view the full range of products.)


    Obviously, my opinion is that Australia has taken the best that it has been able to find in the world of electrical connection devices and improved upon them.

    It is interesting that the Chinese seem to (partly) agree, although they orientate the sockets concerned with the Earth pin upwards - no doubt on the Ah-Sup principle.
    Argentina also uses the "Type I" plug but reverses the Active/Neutral connections.


    While it may be "off the track" I recently (One week ago) made a comment on https://www.youtube.com/watch?v=mY45ZDdiPn4, relating to "Should You Wrap Outlets In Electrical Tape?"

    I believe that I made my opinion quite clear when I wrote : -

    "To quote United States Secretary of Defense Donald Rumsfeld
    "There are known knows; there are things we know we know. We also know there are known unknowns; that is to say we know there are some things we do not know.But there are also unknown unknowns—the ones we don't know we don't know."

    I wish to submit that there are many persons in North America who do not know that the electrical equipment that they install in wall-boxes are of such a primitive design that they would (probably) not be allowed in any other OECD country!
    The very idea of having exposed electrical terminals on the edges of any such device is anathema in most developed countries.
    (The necessity of being able to utilize only a single "solid" and not stranded or multiple wires formed in the correct direction about a "side" screw is also an anathema in those other countries.)

    Because of this, I submit for your consideration images of a dual socket outlet and its connection where there are no bare connections which could connect to any metal box.
    Note that the recessed terminal sockets can easily accommodate up to four 2.5 square millimetre CSA conductors (three are shown) and, when screwed down, the terminal screws are not exposed for accidental contact.
    https://commons.wikimedia.org/wiki/Category:AS/NZS_3112_sockets#/media/Fileual_3_Pin_Socket_Outlet_Wiring.jpg


    These outlets fit into the wall-plates used in North America.
    They include switches for each outlet and cost less than USD$10.
    Of course, they are Australian socket outlets and more details of this design can be seen in https://commons.wikimedia.org/wiki/Category:AS/NZS_3112_sockets#/media/Fileual_3_Pin_Power_Outlet_-_Construction.jpg


    Because up to four conductors (solid or stranded) can be twisted together and connected via set-screws in each rear terminal, there is usually no need for any subsidiary connectors - such as screw-on connectors ("wire-nuts"), which are not allowed in most jurisdictions outside North America."

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    Quote Originally Posted by FrodoOne View Post

    I wish to submit that there are many persons in North America who do not know that the electrical equipment that they install in wall-boxes are of such a primitive design that they would (probably) not be allowed in any other OECD country!
    The very idea of having exposed electrical terminals on the edges of any such device is anathema in most developed countries.
    (The necessity of being able to utilize only a single "solid" and not stranded or multiple wires formed in the correct direction about a "side" screw is also an anathema in those other countries.)
    Fighting words on a US forum or Utube Video

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    Quote Originally Posted by Bros View Post
    Fighting words on a US forum or Utube Video
    However, it has not received any comment (positive or negative) in the last week since it was posted!

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    "Only the SMARTEST babies get electrocuted in England!"

    https://www.youtube.com/watch?v=UEfP1OKKz_Q
    “What a fool believes, he sees. No wise man has the power to reason away”- The Doobie Brothers

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    Quote Originally Posted by UseByDate View Post
    "Only the SMARTEST babies get electrocuted in England!"

    https://www.youtube.com/watch?v=UEfP1OKKz_Q
    I wonder if you noted my comments (of 4 years ago) on this video ?

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    Quote Originally Posted by FrodoOne View Post
    I wonder if you noted my comments (of 4 years ago) on this video ?
    He would have to be dedicated scrolling through those replies.

    I never bothered so what did you say?

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    Quote Originally Posted by Bros View Post
    He would have to be dedicated scrolling through those replies.

    I never bothered so what did you say?
    While you could scroll back 4 years (?) but it is shown below: -
    ---------------------------------------------------------------------------
    Interesting it is (to quote Yoda) that many persons consider that their (whatever) is better than any other competing device!.
    It should be noted that these British 1363 Plug/Socket combinations were designed "in extremis" at the end of WWII.
    (Of course, it is the Socket Outlet which contains the safety features of the shutters and NOT the plug.)

    After WWII, the requirement for a new system of plugs and sockets led to the publishing in 1947 of "British Standard 1363:1947 Fused-Plugs and Shuttered Socket-Outlets."
    (It must be admitted that this was the first time that any published Standard required that the Socket Outlets be protected by "Shutters", operated by the "Earth" pin.
    (However, the fact that "Power Boards" are now allowed to be sold in the UK, as demonstrated at 0:50 where this "shutter" protection can be circumvented, is in indictment on UK governmental regulation authorities to act intelligently. )

    The size of the "Pins" on these BS 1363 plugs seem to be quite incredible, since the Pin size confers no benefit whatsoever.
    The current capacity of any plug/socket combination is determined solely by the Cross Sectional Area (CSA) of the spring loaded Socket Contacts - so, the thickness of the Pins on the plug is irrelevant and is quite a waste of material in BS 3163.
    Note that at around 2:25 in this video there are several errors/deficiencies.The presenter refers to "One giant circuit" at the same time, waving his hands around in a circle.The "One giant circuit" was/is what is called a "Ring Main" or "Ring Circuit"
    (See https://en.wikipedia.org/wiki/Ring_circuit)

    This was used to save copper in the post World War II environment, since a "Ring Circuit", with conductors nominally capable of carrying only 15 A, could carry twice this current to any outlet, if there would be TWO 15 A carrying conductors connected to any such outlet.
    The fuse to protect this would need to be rated at this double current of 30 A BUT the flexible appliance leads were/are rated at much lesser values (with a current maximum of 13 A).
    Hence, the need to use a lower rated fuse at each plug.

    It should be noted that fuses and circuit breakers are provided to protect ONLY the wiring at the premises and the leads connecting to the appliances from overheating. They do NOT protect the appliances themselves - nor anything else, including human beings.

    At 2:35, the presenter states Brown is "Live".
    It is a common misconception that "L" in electrical situations stands for "Live" - It does NOT. "L" stands for "Line" - as opposed to "N" for " Neutral".

    At 2:45 he states, referring to the Earth/Ground wire "If there is a problem, all the electricity will go away from people."
    NO! The function of the Ground/Earth wire (connected to the metal "body" of many appliances). is to cause the Fuse to "blow" or the Circuit Breaker to "Trip", if the "Line" becomes connected to this "touchable" (Earthed) metal.
    In this way it DOES "protect people", but only because it causes the "Line" to be open-circuited - sometimes, quite dramatically.

    It should also be noted that insulated "sleeved pins" were NOT required in the original specification for BS 1363.
    It was not until August 1984: BS 1363:1984 that this was specified. (37 years later.)

    Here I will note that the far more elegant AS/NZS 3112 plug /socket combination has been available with "shutters" on the socket outlet, if required, for over forty years and insulated Pins have been required on these plugs since 3 April 2005.
    The plugs are available in at least three formats, with the lead descending either vertically, sideways or horizontally. - with the "sideways" connection (at the 4:30 O'Clock position) being the most convenient and now usual.
    These plugs also have the path for the Earth wire being longer, so that it is likely that it will be the last conductor to disconnect. In addition, since the Australian/NZ Earth pin is always at the lower side, it is likely that it will be the last pin to disconnect if the lead is pulled downwards. This is in contradiction for the top mounting position for the Earth pin with BS 1363.

    It is quite notable that Chinese Socket Outlets now often incorporate what is basically an Australian/New Zealand Socket Outlet (although it is presented upside down and with the Neutral and Line connections reversed), together with a European "Schuko" connection, which may accept Europlugs and non-earthed CEE 7/17 plugs.

    ------------------------------------------------------------------------------------------------------------

    I do know that there are "arguments" that the pin size is for mechanical strength and not current carrying capacity.
    However, the thinner pins on an Australian plug can usually be bent back if deformed.





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    Quote Originally Posted by FrodoOne View Post
    While you could scroll back 4 years (?) but it is shown below: -

    You would have to be joking as the replies are all over the place and I couldn't find any way to put them in chronological order so I gave up

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    Quote Originally Posted by Bros View Post
    You would have to be joking as the replies are all over the place and I couldn't find any way to put them in chronological order so I gave up
    Click on "SORT BY"/"Newest First".

    Of course, when I click on "Top Comments" mine come to the top

    (However, there are many comments in the last 4 years and nobody has commented on mine.)

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    Quote Originally Posted by FrodoOne View Post
    Of course, when I click on "Top Comments" mine come to the top

    (However, there are many comments in the last 4 years and nobody has commented on mine.)
    Preferential treatment

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    Quote Originally Posted by FrodoOne View Post
    While you could scroll back 4 years (?) but it is shown below: -
    ---------------------------------------------------------------------------
    Interesting it is (to quote Yoda) that many persons consider that their (whatever) is better than any other competing device!.
    It should be noted that these British 1363 Plug/Socket combinations were designed "in extremis" at the end of WWII.
    (Of course, it is the Socket Outlet which contains the safety features of the shutters and NOT the plug.)

    Thank you. I would not have had the patience to scroll back 4 years.
    I will respond to your post in parts. Not many will have the time to re-read long posts.

    Well spotted. The shutters are in the outlet. Maybe the presenter in the video chose to simplify the title. He could have titled the video “British Plugs and Socket-Outlets Are Better Than All Other Plugs and Socket-Outlets, And Here's Why”.
    “What a fool believes, he sees. No wise man has the power to reason away”- The Doobie Brothers

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    Quote Originally Posted by FrodoOne View Post
    While you could scroll back 4 years (?) but it is shown below: -
    ---------------------------------------------------------------------------


    After WWII, the requirement for a new system of plugs and sockets led to the publishing in 1947 of "British Standard 1363:1947 Fused-Plugs and Shuttered Socket-Outlets."
    (It must be admitted that this was the first time that any published Standard required that the Socket Outlets be protected by "Shutters", operated by the "Earth" pin.
    (However, the fact that "Power Boards" are now allowed to be sold in the UK, as demonstrated at 0:50 where this "shutter" protection can be circumvented, is in indictment on UK governmental regulation authorities to act intelligently. )

    He admits in the video that it is a badly designed “power board”. Even so it still takes two actions to get to the potentially live conductors. Well designed “power boards” can be bought. Some shutter designs need all three plug “pins” to be present before they open. Criticism can also be directed at the Australian Government for allowing “power boards” to be sold that circumvent the socket-outlet design that places the “Earth” socket at the bottom. After all most “power boards” are not mounted on the wall, they are mostly left on the floor. Ie no bottom.
    “What a fool believes, he sees. No wise man has the power to reason away”- The Doobie Brothers

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    Quote Originally Posted by FrodoOne View Post
    While you could scroll back 4 years (?) but it is shown below: -
    ---------------------------------------------------------------------------

    The size of the "Pins" on these BS 1363 plugs seem to be quite incredible, since the Pin size confers no benefit whatsoever.
    The current capacity of any plug/socket combination is determined solely by the Cross Sectional Area (CSA) of the spring loaded Socket Contacts - so, the thickness of the Pins on the plug is irrelevant and is quite a waste of material in BS 3163.

    Not really. The design is so robust that it does not wear out. The plug is recyclable and can become a family heirloom and be passed on to many descendants avoiding the need for many throw away plugs. The “pins” do not bend. Surely the better design is a plug that does not fail rather than one that does but is easy to repair by bending the “pins” back?
    “What a fool believes, he sees. No wise man has the power to reason away”- The Doobie Brothers

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    Quote Originally Posted by FrodoOne View Post
    While you could scroll back 4 years (?) but it is shown below: -
    ---------------------------------------------------------------------------
    The presenter refers to "One giant circuit" at the same time, waving his hands around in a circle.The "One giant circuit" was/is what is called a "Ring Main" or "Ring Circuit"
    (See https://en.wikipedia.org/wiki/Ring_circuit)

    This was used to save copper in the post World War II environment, since a "Ring Circuit", with conductors nominally capable of carrying only 15 A, could carry twice this current to any outlet, if there would be TWO 15 A carrying conductors connected to any such outlet.
    The fuse to protect this would need to be rated at this double current of 30 A BUT the flexible appliance leads were/are rated at much lesser values (with a current maximum of 13 A).
    Hence, the need to use a lower rated fuse at each plug.

    I think this is just a myth. There does not seem to be any written evidence (design requirements), to my knowledge, that the Ring Circuit was designed to “save copper”.
    Let's say a house is wired with a ring circuit. The maximum power that circuit can distribute is 240V times 30A ie 7.2kW. Now break the ring circuit at midpoint and provide 2 fuses of 20A ie two radial circuits. Now this configuration can distribute 2 times 240V times 20A ie 9.6 kW which is greater than the ring circuit and it uses slightly less copper.
    The radial configuration can carry more power than the ring circuit (9.6 kW) but with the limitation that the power must not be greater than half full load in each circuit (4.8 kW). The ring circuit can carry maximum power to any point in the circuit but with the limitation that the maximum power is reduced to ¾ (7.2 kW) that of the radial configuration.
    Most British houses are wired with a combination of ring circuits and radial circuits (and some hybrid). British Standard (BS) does not mandate that the ring circuit is used. It is up builder/owner whether the socket-outlets are wired in a ring circuit or radial configuration.
    “What a fool believes, he sees. No wise man has the power to reason away”- The Doobie Brothers

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    Quote Originally Posted by UseByDate View Post
    I think this is just a myth. There does not seem to be any written evidence (design requirements), to my knowledge, that the Ring Circuit was designed to “save copper”.
    Let's say a house is wired with a ring circuit. The maximum power that circuit can distribute is 240V times 30A ie 7.2kW. Now break the ring circuit at midpoint and provide 2 fuses of 20A ie two radial circuits. Now this configuration can distribute 2 times 240V times 20A ie 9.6 kW which is greater than the ring circuit and it uses slightly less copper.
    The radial configuration can carry more power than the ring circuit (9.6 kW) but with the limitation that the power must not be greater than half full load in each circuit (4.8 kW). The ring circuit can carry maximum power to any point in the circuit but with the limitation that the maximum power is reduced to ¾ (7.2 kW) that of the radial configuration.
    Most British houses are wired with a combination of ring circuits and radial circuits (and some hybrid). British Standard (BS) does not mandate that the ring circuit is used. It is up builder/owner whether the socket-outlets are wired in a ring circuit or radial configuration.
    However, in https://electrical.theiet.org/media/...let-system.pdf (although copper is not specifically mentioned) it is stated
    "It was realised that a post-war Britain would continue to suffer from a massive shortage of raw materials and it was estimated that the proposed changes to the ring-circuit and single-pole fusing would show a saving of approximately 25% compared with pre-war regulations" and
    "the ring circuit system required 30% less cable and can save about 25% in the cost of the wiring of a house and concludes: “There is no doubt that in modern domestic premises that are to be adequately provided with electric points, the cheapest and safest system is to use a ring final circuit.”"

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    Quote Originally Posted by FrodoOne View Post
    However, in https://electrical.theiet.org/media/...let-system.pdf (although copper is not specifically mentioned) it is stated
    "It was realised that a post-war Britain would continue to suffer from a massive shortage of raw materials and it was estimated that the proposed changes to the ring-circuit and single-pole fusing would show a saving of approximately 25% compared with pre-war regulations" and
    "the ring circuit system required 30% less cable and can save about 25% in the cost of the wiring of a house and concludes: “There is no doubt that in modern domestic premises that are to be adequately provided with electric points, the cheapest and safest system is to use a ring final circuit.”"
    Your referenced document states that the terms of reference (design requirements) of the study was to provide improved amenities in post-war housing.

    “In its day, it must have been almost revolutionary in its outlook with many radical proposals aimed at providing improved amenities in post-war housing”.....“The emphasis throughout this study has been the economical provision of many sockets-outlets”.

    Prior to this study each major room in a house would probably have had only one sockets-outlet fitted. Each of these sockets-outlets would have been connected back to the fuse box via a dedicated circuit. Having only one sockets-outlet per room would have meant that an extension cable would be needed if an appliance was located far from the sockets-outlet. If two appliances were to be operated simultaneously then a “double adaptor” would be needed. Both are not particularly safe.

    The study was to design a system that would enable as many sockets-outlets as was needed and a simple method of adding more as required ie no limit to the number of sockets-outlets. This was required because of the proliferation of domestic appliances that had just started to take place. The old system had the problem that each sockets-outlet had its own fuse; so adding sockets-outlets meant another fuse. Thus the number of sockets-outlets was limited by the size of the fuse box. The solution was to move the fuse to the appliance plug. The house would be fitted with one power cable that “daisy chained” the sockets-outlets which meant only one fuse was required in the fuse box to protect the sockets-outlet cable. The fact that this design was economical in is use of copper was a by-product, not the primary design requirement.

    To say that the ring-circuit was introduced to “save copper” is as silly as saying cars were introduced to reduce the amount of horse merda on the road.
    “What a fool believes, he sees. No wise man has the power to reason away”- The Doobie Brothers

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    Quote Originally Posted by UseByDate View Post
    To say that the ring-circuit was introduced to “save copper” is as silly as saying cars were introduced to reduce the amount of horse manure on the road.
    Did a final ring circuit result in lighter gauge wire!

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    Quote Originally Posted by phild01 View Post
    Did a final ring circuit result in lighter gauge wire!
    Lighter than what?
    “What a fool believes, he sees. No wise man has the power to reason away”- The Doobie Brothers

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    When I think about it you have two supply directions effectively doubling power handling of a given size of cable.

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    No. The current carrying capacity of cable has to be at least two thirds that of the over current protection. (fuse). This was/is normally 30A. So the cable has to be 20A. This is because the only load that shares its current equally through both conductors is the one half way around the loop. All other loads pass more current through the shorter path to the fuse box than the longer path.
    As far back as I can remember, maybe 60 years, 20A cable would be 2.5mm.
    “What a fool believes, he sees. No wise man has the power to reason away”- The Doobie Brothers

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    What I am getting at is the ringed cable has each end of the cable connected at the fuse, current carrying capacity is significantly more than just having one end of the cable connected at the fuse. The appliance gets what it needs from both ends not just one end. The current carrying capacity from both ends won't change significantly whether one is longer or shorter within the run range of a residence at the time.

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    Quote Originally Posted by phild01 View Post
    What I am getting at is the ringed cable has each end of the cable connected at the fuse, current carrying capacity is significantly more than just having one end of the cable connected at the fuse. The appliance gets what it needs from both ends not just one end. The current carrying capacity from both ends won't change significantly whether one is longer or shorter within the run range of a residence at the time.
    It is not the current carrying capacity that matters it is the actual current that is being carried.

    Let us say we have a 30 metre ring circuit. The first socket-outlet is 3 metre from the fuse box. The load at the outlet is say 20A.
    How much current will flow via the 3 metre path?
    How much current will flow via the 27 metre path?
    “What a fool believes, he sees. No wise man has the power to reason away”- The Doobie Brothers

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    I don't think the difference would be great, someone might calculate it.

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    Quote Originally Posted by phild01 View Post
    I don't think the difference would be great, someone might calculate it.
    Where are friends when you need them?

    Ok.
    The 27 metre path is 9 times the resistance of the 3 metre path. (27 divided by 3)
    Both paths have the same voltage drop. (They are connected together in parallel)
    Ohms law is Voltage = Current times Resistance
    Therefore the 3 metre path carries 9 times the current that is carried by the 27 metre path.


    Therefore with a load of 20A the 3 metre path carries 18A and the 27 metre path carries 2A
    Ie only 10% of “power” is carried by the long path of the ring-circuit.
    “What a fool believes, he sees. No wise man has the power to reason away”- The Doobie Brothers

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    Not sure about that conclusion as resistance rises with current draw. Be good if someone could affirm what happens here. I suppose you could crudely set up a 30m ring circuit with 1 or 1.5mm and test the current draw each end of the cable of a 4800 heater element 3m in.

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    The temperature coefficient of copper at room temperature is 0.393 percent per degree C.
    A ten degree rise in temperature only changes the resistance by 4%.
    “What a fool believes, he sees. No wise man has the power to reason away”- The Doobie Brothers

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    Agree with that, just not sure that when current draw is near capacity, that the shorter length increased resistance will consequently have increased current draw from the longer length. Why I was suggesting a 4.8kW element experiment with under-rated cable.

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    Ok
    Now we have a ring-circuit 30 metres long. There is a 20A load 3 metres from the start of the ring-circuit and a 20A load 3 metres from the end of the ring-circuit. (40A fused supply).
    How much current flows in the cables between the loads and the fuse?
    How much current flows in the cable between the two loads?
    “What a fool believes, he sees. No wise man has the power to reason away”- The Doobie Brothers

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    Quote Originally Posted by UseByDate View Post
    The 27 metre path is 9 times the resistance of the 3 metre path. (27 divided by 3)
    Both paths have the same voltage drop. (They are connected together in parallel)
    Ohms law is Voltage = Current times Resistance
    Therefore the 3 metre path carries 9 times the current that is carried by the 27 metre path.


    Therefore with a load of 20A the 3 metre path carries 18A and the 27 metre path carries 2A
    Ie only 10% of “power” is carried by the long path of the ring-circuit.
    (I agree with the above but came up with the answer by a "calculation".)

    I pondered the question overnight and modified it slightly to :
    "Let us say we have a 30 metre ring circuit. The first socket-outlet is 3 metre from the fuse box. The load at the outlet is a resistance designed to draw 20 A when connected across 240 V."
    since this would be the typical situation, in "practice".

    Call the 3 m circuit A and the 27 m circuit B.
    The resistance of 2.5 mm CSA copper wire is 6.9 mΩ per metre. (Calculated form data in https://en.wikipedia.org/wiki/American_wire_gauge)

    There are two wires for each circuit.
    Hence, the resistance of A is 6.9 * 2 * 3 = 41.4 mΩ (0.0414 Ω) and
    the resistance of B is 6.9 * 2 * 27 = 372.6 mΩ (0.3726 Ω)

    These two resistances are in parallel - in series with the load, across 240 V.
    The total Line resistance is 0.03726 in series with the 12 Ω Load so the current will be 240 /(0.03726 +12) = 19.93809 A

    The voltage drop across the parallel Line resistors will be (I*R) 19.93809 * 0.03726 = 0.742893 V
    So, the current in A will be E/RA = 0.742893 / 0.0414 =17.94428 A and
    the current in B will be E/RB = 0.742893 / 0.3726 = 1.99381 A

    Current A / Current B = 17.94428 / 1.99381 = 9


    As I had set up a spread sheet to do the calculation, I then calculated the currents for a "take off" point at each metre to the mid-point of the "Ring".

    Length Current
    A A B Total A/B
    0 20.00000 0.00000 20.00000
    1 19.31186 0.66593 19.97779 29.00
    2 18.62668 1.33048 19.95716 14.00
    3 17.94428 1.99381 19.93809 9.00
    4 17.26451 2.65608 19.92059 6.50
    5 16.58719 3.31344 19.90063 5.01
    6 15.91216 3.97804 19.89020 4.00
    7 15.23928 4.63804 19.87732 3.29
    8 14.56838 5.29759 19.86597 2.75
    9 13.89930 5.95684 19.85614 2.33
    10 13.23189 6.61594 19.84783 2.00
    11 12.56599 7.27505 19.84104 1.73
    12 11.90146 7.93430 19.83576 1.50
    13 11.23813 8.59386 19.83199 1.31
    14 10.57586 9.25387 19.82973 1.14
    15 9.91449 9.91449 19.82898 1.00

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    The ring circuit allows extra circuit rating which was an initial point I made, although seemingly out by a significant factor for short distances. Though I still would like to know what happens when the load increases resistance when it (the load current) is high.
    It confounds me that halfway the load rating would be high for the circuit yet low when the distances are different.

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    Quote Originally Posted by UseByDate View Post
    Now we have a ring-circuit 30 metres long. There is a 20A load 3 metres from the start of the ring-circuit and a 20A load 3 metres from the end of the ring-circuit. (40A fused supply).
    How much current flows in the cables between the loads and the fuse?
    How much current flows in the cable between the two loads?
    Now we have a ring-circuit 30 metres long.
    There is a 20A load 3 metres from the start of the ring-circuit and a 20A load 3 metres from the end of the ring-circuit. (40A fused supply).
    (Should read : "There is a 20 A load 3 metres from the start on one side of the ring-circuit and a 20 A load 3 metres from the start on the other side of the ring-circuit.")
    (A “Ring” circuit does not have an “End”. It has two “Starting Points”.)

    How much current flows in the cables between the loads and the fuse?
    (Should read “How much current flows in the cables between each load and the fuse.)
    Answer. 20 A (neglecting the loss due to the voltage drop of 0.825153 V. Actually 19.93124 A - with a 12 Ω Load)

    How much current flows in the cable between the two loads?
    Answer. Nil (Because the voltage drops in the two 3 m lengths from the "Start" are the same - with balanced Loads - so there is no potential difference between these two points.

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