# Forum More Stuff Debate & Technical Discussion  Electrical DIY questions

## elkangorito

I've put together some questions for DIYers to answer. Please, this is only for non-qualified people (not qualified as an electrician). 
The object of this test is to assist those who wish to expand their knowledge on electrical DIY. It is in no way intended to ridicule or attack any individual. 
Please keep answers brief. 
To other "qualified" posters, please refrain from providing any answers until about 2 weeks from now. I shall not provide any answers until about the 5th of July, however, I will provide further explanation regarding questions prior to this date. 
Here is the test.    
Electrical questions for DIYers only.  
1.
When looking at a GPO, which pin is the "active"?  
2.
You have just purchased a new electric welder and want to install a power circuit for it. You have 3 spare circuit breaker spaces in your recently installed consumer unit & an existing 32mm underground conduit going from the consumer unit to your shed. The length of the conduit run is 20m & it has 1 x 90 degree bend/elbow in it. The existing conduit contains a 2.5mm 2c+E TPS cable supplying 2 x DGPO's & 2 x 36 watt fluoros. The welder's rating plate says that it is single phase, 230 volt, 50Hz & 15 amps at 100% duty cycle. It will be plugged into a 15 amp outlet. 
a] What type of PD (protective device) will you use?
b] What are the ratings of the PD?
c] What type & size of cable will you use?  
3.
You have just found a 10m long extension lead in your shed. It appears to be in good condition & does not have a plug or socket connected on either end. The wire colours are yellow, brown & green. 
a] What colours represent active, neutral & earth?
b] What tests/checks should be carried out prior to using this lead?  
4.
Why is the active/neutral "polarity" of GPO's etc important?  
5.
You have just purchased components for your new Home Theatre system, which comprises of a DVD player, a 100 watt per channel (RMS audio output power) audio amplifier & a huge plasma screen plus tuner. You also want to use some of your old equipment like a turn table, a cassette player & a CD player (you don't want to wear out your DVD player playing music CD's). In total, you have 7 items (7 plugs) but you only have 1 spare DGPO (double power outlet) in your lounge room. 
a] What can you do in order to safely supply all of this equipment with electricity?  
6.
What does a circuit breaker protect?  
7.
Generally speaking, what is the maximum size circuit breaker used with the following; 
a] 1mm TPS cable.
b] 1.5mm TPS cable.
c] 2.5mm TPS cable.
d] 4mm TPS cable.  
8.
You have a very large shed with 20 fluorescent light fittings. Each fitting has 2 x 40 watt tubes & a capacitor fitted. After 2 years, the 10 amp light switch mechanism fails & you wish to buy a replacement. Assume that the supply voltage is 230 volts. What do you buy?  
9.
You have an inquisitive young child who, despite the fact that you have protective covers on the GPO's in his/her room, is still able to remove these covers & stick things into the GPO's. His/her activity has lead to the RCD of that circuit being tripped on numerous occasions, which is somewhat inconvenient (circuit serves more than one room). The RCD protecting the circuit is rated at 30mA.
What can you do to; 
a] provide added protection for the child?
b] reduce the inconvenience to others?  
10.
Describe how you would connect 3 x 1.5mm multi-strand wires into a BP connector?  
11.
Where CAN"T you install a junction box?

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## atregent

Ooh, a quiz!   1. Top left  2. This is definately something for a sparky, but I would guess a 25A breaker on a 4mm² TPS cable. 15A points, as far as I'm aware, should be on a separate breaker.  3a] What colours represent active, neutral & earth?Never seen that colour combo before, but I would assume that brown is active, green is earth and therefore yellow is neutral.   3b] What tests/checks should be carried out prior to using this lead?Make sure the insulation is ok, check the resistance of and between the conductors. Personally, I'd just buy a new lead. $20 for 20m at Bunnings, can't go wrong!  4. Only the active is switched, so the GPO could still be live with the power switched off  5. I've got most of that stuff plugged into a standard powerboard with an overload protector, which is working ok for me. To be on the safe side, and something that I'm intending to do, is get a surge protected board. If you wanted to separate one thing into the other half of the DGPO, I'd put the plasma in there.   6. The wiring   7. Depends on where the cable is, but generally speaking, I'd say 10A, 16A, 20A, and 25A   8. A better quality switch? I don't know what the startup current on a fluro is, but 1600W of light should be fine for a 10A switch. Perhaps splitting it up into a couple of separate circuits would be a better idea though.  9. The expensive option would be to install a new circuit for the troublesome child, with it's own RCD. A more realistic option would be to install RCD protected outlets in it's room with a rating lower than 30mA.  10. Strip off a bit more insulation than I need, twist them all tightly together with pliers, trim off the tip to make it nice and neat. I usually twist (that is to say, if I actually did this myself ) them all so the insulated part of the wires are twisted as well.  11. Anywhere you can't get at it 
How'd I do?

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## dambat

4.
Why is the active/neutral "polarity" of GPO's etc important? 
I think you mean active/neutral assignment.  AC polarity is something different, and refers to relationship different phases at the same frequency have to each other. 
Some other questions :Redface: 
(12) Why do high voltage mains lines have three carriers while low voltage have four?
(13) Will the RCD still protect the circuit without an earth (I know this is vague)?
(14) Why is 3 phase 415V, not 3x240V?
(15) Why is a good earth at the switch box important?

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## atregent

I feel like I'm in an interview now, hope I get the job! 
12. No idea about this one. I guess a linesman job is not for me! 
13. As far as I'm aware, an RCD works by measuring the difference in current going out and coming back, so, yes, I would imagine it would work without an earth. Aren't the neutral and earth connected at the switchboard anyway? 
14. 240V is measured from active to neutral, 3 phase is measured active to active. 
15. Because all the earths feed back to the switchboard, and, I think, the neutral is also connected to earth.

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## rrobor

Can I ask a question. Asume I am colour blind and can not tell brown from green but have an ohm meter, it is not unsafe for me to wire your extention lead using any sequence provided I maintain the sequence from plug to socket. Your other question as to the child suggests that you can protect the child from harm in some way with a breaker of some sort. People die with electric guitars with 30mA fuses in them. I believe the figure is about 15uA across the heart will stop it beating so the answer to that is Paddle the childs behind because there is no way to protect a socket from idiots determined to kill themselves.

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## elkangorito

> How'd I do?

  I'll tell you after the 5th of July.   

> 4.
> Why is the active/neutral "polarity" of GPO's etc important? 
> I think you mean active/neutral assignment.  AC polarity is something different, and refers to relationship different phases at the same frequency have to each other.

  No. I mean polarity as per ASNZ3000:2007 Clause 8.3.7    

> Can I ask a question. Asume I am colour blind and can not tell brown from green but have an ohm meter, it is not unsafe for me to wire your extention lead using any sequence provided I maintain the sequence from plug to socket. There's no doubt that it would be safe to use but it wouldn't be to code. 
> Your other question as to the child suggests that you can protect the child from harm in some way with a breaker of some sort. People die with electric guitars with 30mA fuses in them. I believe the figure is about 15uA across the heart will stop it beating so the answer to that is Paddle the childs behind because there is no way to protect a socket from idiots determined to kill themselves. I can assure you that a 30mA fuse is a vastly different thing compared to an RCD.
> Also, according to ASNZ3000:2007, RCDs with a sensitivity of 30 mA are designed to operate before fibrillation of the heart occurs. RCDs with a sensitivity of 10 mA are designed to operate before muscular contraction, or inability to let go occurs. Muscular contraction can result in inability to breathe.

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## rrobor

The major issue people forget when they get any safety device is it doesnt protect fools. Your question is a child sticking things in the power socket. Let us assume two nails. Shoves one in the negative hole and nothing happens takes the next one and shoves it in the live hole whilst still holding the other. The fuse or circuit protector will not blow nor will any other device, the child is a load like any other and the child fries because it has less than the 15A or so across the heart but not enough to trip a cutout. My arguement is not intended to be for the sake of arguement it is intended to show that you can and should use the best protection you can but in the end you can not fully protect against every instance. Having a question as to a child with a passion to stick wires in sockets thinking you can protect the child  by any other means than educating the child is
false

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## Master Splinter

1.
Left hand slanty one.  
2.
I'd pass on this as I don't like playing with switchboards. But in that light... 
a] What type of PD (protective device) will you use? A sparkie.
b] What are the ratings of the PD? His problem
c] What type & size of cable will you use? Ditto  (see also Table C6 in AS3000 which I am too tired to work through at the moment!  I'd also check for derating and voltage drop and look at Table B1 to select a PD)  
3.
You have just found a 10m long extension lead in your shed. It appears to be in good condition & does not have a plug or socket connected on either end. The wire colours are yellow, brown & green. 
a] What colours represent active, neutral & earth? Doesn't comply with any currently allowable colour combination that I know of so I'd chuck it...its cheaper to buy a whole lead than a plug and socket for a bit of old wire of dubious parentage.  You could be fussy and sleeve it (green is earth, sleeve the brown as red, and the yellow as black) but I'd still assign it to the trash. 
b] What tests/checks should be carried out prior to using this lead? That the garbage man is coming.  
4.
Why is the active/neutral "polarity" of GPO's etc important? To ensure that you are switching the active and not the neutral.  ie the connected appliance is not live all the way to the switch (or the earth!).   
5.
You have just purchased components for your new Home Theatre system, which comprises of a DVD player, a 100 watt per channel (RMS audio output power) audio amplifier & a huge plasma screen plus tuner. You also want to use some of your old equipment like a turn table, a cassette player & a CD player (you don't want to wear out your DVD player playing music CD's). In total, you have 7 items (7 plugs) but you only have 1 spare DGPO (double power outlet) in your lounge room. 
a] What can you do in order to safely supply all of this equipment with electricity?  A honkin' big 8-way power board with surge protection and line filters, you've only got about 1500 watts draw as a maximum there.  Anything else would look wanky and make the house hard to sell if you had two stacked 4-way gpos.  
6.
What does a circuit breaker protect? The fixed wiring. 
7.
Generally speaking, what is the maximum size circuit breaker used with the following; 
a] 1mm TPS cable.16 amp
b] 1.5mm TPS cable. 20 amp
c] 2.5mm TPS cable. 25 amp
d] 4mm TPS cable. 32 amp  (thats assuming unenclosed in air...10, 16, 20, 25 for partially surrounded in thermal insulation.  Or see Table C5)  
8.
You have a very large shed with 20 fluorescent light fittings. Each fitting has 2 x 40 watt tubes & a capacitor fitted. After 2 years, the 10 amp light switch mechanism fails & you wish to buy a replacement. Assume that the supply voltage is 230 volts. What do you buy? Same thing again, as the sparkie did it right the first time... 
Or two switches as that's a silly number of lights to turn on just to check if the cat is in there.   
Or maybe some contactors so I can get that industrial 'chunk...chunk...chunk' sound as they come on in banks.  That would be seriously cool (but you woudn't be able to hear them over the sound of how awesome I am for doing it that way). 
9.
You have an inquisitive young child who, despite the fact that you have protective covers on the GPO's in his/her room, is still able to remove these covers & stick things into the GPO's. His/her activity has lead to the RCD of that circuit being tripped on numerous occasions, which is somewhat inconvenient (circuit serves more than one room). The RCD protecting the circuit is rated at 30mA.
What can you do to; 
a] provide added protection for the child?
b] reduce the inconvenience to others? 
1) Leave as is and think of it as evolution in action, or
2) Remove power point, make the wires safe in their own little BP connectors, tuck in wall, place blank cover where power point used to be.  No power point, no danger.  (if the little $#&@@*!**% wants to break through the plasterboard wall they'll be wishing the RCD hadn't tripped!!!)  
10.
Describe how you would connect 3 x 1.5mm multi-strand wires into a BP connector? Strip to length, check for nicks, twist together in their natural direction, swear as I get jabbed by one bent bit of wire sticking out at a funny angle, slide in and screw tight. Make sure there is no exposed wire beyond the terminal.  I also wrap insulation tape around the TPS sheaths to keep them together and keep any strain off the actual fastener. 
11.
Where CAN"T you install a junction box? Anywhere that it is inaccessable (ie hidden in a wall)

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## rrobor

Put me in for seconding that only diff is Id paddle the brats behind.

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## elkangorito

> The major issue people forget when they get any safety device is it doesnt protect fools. Your question is a child sticking things in the power socket. Let us assume two nails. Shoves one in the negative hole and nothing happens takes the next one and shoves it in the live hole whilst still holding the other. The fuse or circuit protector will not blow nor will any other device, the child is a load like any other and the child fries because it has less than the 15A or so across the heart but not enough to trip a cutout. My arguement is not intended to be for the sake of arguement it is intended to show that you can and should use the best protection you can but in the end you can not fully protect against every instance. Having a question as to a child with a passion to stick wires in sockets thinking you can protect the child  by any other means than educating the child is
> false

  You are correct..."standards" & safety devices don't protect fools. I think that most people on this forum are well aware of this. 
The purpose of this little quiz is to inform people what can "resonably" be done to afford acceptable electrical safety & good work practice, without splitting too many hairs. 
The question is realistic & if you care to think beyond "protective devices", you will find that there is more than one solution to this problem.   

> 1. Left hand slanty one...........

  Some humorous & good answers there Splinter. Thanks. :2thumbsup:

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## rrobor

Sorry I dont think it is. We are talking about a child playing with a socket and you are implying that there is some way to protect the child other than education or some form of disincentive. Now Master splinters answer was take the socket away. Now that fixes that point but the kid thinks its a game so now looks for other sockets. You cant watch a child for every second and you cant lock the child away. You agree than no protection device will stop certain ways a person gets caught across power. Now Im not being pedantic but I find it very dangerous to allow people to believe that they protect themselves fully with some form of earth leakage trip. And yes I dont blame you, most people believe they are safe after all they saw the adds on TV with the guy puting a knife in the toaster. I may be on my soap box but it annoys me when dangers exist and no explanations are given as to the folly of trusting protection devices. The only safe method of avoiding electrocution is to be aware and not touch things you shouldnt. Protection devices save many lives and are a great addition but they are not fail safe and must never be regarded as such.

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## elkangorito

My response in blue.   

> Sorry I dont think it is. We are talking about a child playing with a socket and you are implying that there is some way to protect the child other than education or some form of disincentive. Now Master splinters answer was take the socket away.  Just how many hairs do you wish to split? The quiz question is hypothetical & is purely designed to enhance thinking about certain situations & not to cover every single idiosyncratic behavioural problem of human beings.  
> Now that fixes that point but the kid thinks its a game so now looks for other sockets. You cant watch a child for every second and you cant lock the child away. You agree than no protection device will stop certain ways a person gets caught across power. Now Im not being pedantic (yes you are) but I find it very dangerous to allow people to believe that they protect themselves fully with some form of earth leakage trip. And yes I dont blame you, most people believe they are safe after all they saw the adds on TV with the guy puting a knife in the toaster. I may be on my soap box but it annoys me when dangers exist and no explanations are given as to the folly of trusting protection devices. The only safe method of avoiding electrocution is to be aware and not touch things you shouldnt. Protection devices save many lives and are a great addition but they are not fail safe and must never be regarded as such.  Nobody will argue against what you are saying but the most that current technology (and the wiring standard) provides is the combination of an appropriately earthed electrical system with the added protection of RCD's. This is all that an Australian can do. Unfortunately, the Australian Wiring Rules don't cover idiosyncratic behaviour of humans with electrical equipment/installations. 
> What you are talking about totally departs from the purpose of this thread, which is "to be able to safely & adequately, within the confines of common sense, carry out electrical work within your own home".

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## chrisp

Formally, as I'm considered to be "non-qualified", I assume I can join in?_ 
1. When looking at a GPO, which pin is the "active"?_ 
Looking at the outlet, and starting from Earth pin, the pins are E A N in a clockwise direction.  _2. You have just purchased a new electric welder and want to install a power circuit for it. You have 3 spare circuit breaker spaces in your  recently installed consumer unit & an existing 32mm underground conduit going from the consumer unit to your shed. The length of the conduit run is 20m & it has 1 x 90 degree bend/elbow in it. The existing conduit contains a 2.5mm 2c+E TPS cable supplying 2 x DGPO's & 2 x 36 watt fluoros. The welder's rating plate says that it is single phase, 230 volt, 50Hz & 15 amps at 100% duty cycle. It will be plugged into a 15 amp outlet._  _a] What type of PD (protective device) will you use?
b] What are the ratings of the PD?
c] What type & size of cable will you use?_ 
Keep answers brief?  I'll try to be brief... 
a] RCD/MCB type-C or perhaps type-D depending upon the welder in-rush current
b] 16A or 20A (see below) 
c] 2.5 mm2 or 4 mm2 copper V-90 TPS (see below) 
If using 2.5mm2, the voltage drop will be approximately 2.4%
If using 4mm2, the voltage drop will be approximately 1.5%  
A few issues that may revise the above:Is the cable run in conduit above ground as well?
What are the installation conditions outside the conduit run?  
Are there any runs in thermal insulation or in hot areas?If the conduit run is also above ground (in air), and 2.5mm2 cable is used - and shares the same conduit with the existing circuit, both CBs will need to be reduced to 16A.  If the conduit runs above ground and it is partially surrounded by thermal insulation, then then a separate conduit will be required for the new circuit (and it will also need to be spaced from the existing conduit).  Sharing the conduit if it is partially surrounded by thermal insulation will require the existing circuit to be derated below 14A (10A CB), and 4mm2 cable to be used for the new circuit (good luck drawing the cable). 
If the cable runs completely surrounded through more than 150mm of thermal insulation, then 4mm2 will be required (with a 16A CB).  The new circuit would need to be separated from the other circuit. 
Note, 4mm2 may not be able to go down the same conduit as the 2.5mm2 depending upon the physical size of the 2.5mm2 cable.   
Also, there maybe issues with withdrawing/drawing the cables through the conduit.   *3. You have just found a 10m long extension lead in your shed. It appears to be in good condition & does not have a plug or socket connected on either end. The wire colours are yellow, brown & green. 
a] What colours represent active, neutral & earth?
b] What tests/checks should be carried out prior to using this lead?* 
a] So it is a piece of cable with yellow, brown & green cores?  It is hardly an "extension lead" without a plug and socket!   
The cable isn't suitable for use as an extension cord.  The colour of the cores don't comply with standards and I'd question whether the cable is appropriately suited or rated for the job.  Also, the standard doesn't allow yellow or green to be used as a non-earth. 
b] NA (but I'm happy to answer if standard cable is assumed.)  _4. Why is the active/neutral "polarity" of GPO's etc important?_ 
Most GPOs only have a SPST switch.  The switch should be in the active.  *5. You have just purchased components for your new Home Theatre system, which comprises of a DVD player, a 100 watt per channel (RMS audio output power) audio amplifier & a huge plasma screen plus tuner. You also want to use some of your old equipment like a turn table, a cassette player & a CD player (you don't want to wear out your DVD player playing music CD's). In total, you have 7 items (7 plugs) but you only have 1 spare DGPO (double power outlet) in your lounge room. 
a] What can you do in order to safely supply all of this equipment with electricity?* 
Use a powerboard  _6. What does a circuit breaker protect?_ 
The fixed wiring  _7. Generally speaking, what is the maximum size circuit breaker used with the following; 
a] 1mm TPS cable.
b] 1.5mm TPS cable.
c] 2.5mm TPS cable.
d] 4mm TPS cable._ 
In air:  a] 16A, b] 20A, c] 25A, d] 32A
Partially surround by thermal insulation: 10A, 16A, 20A, 25A
Completely in thermal insulation: 8A, 10A, 16A, 20A
Enclosed - in air: 13A, 16A, 20A, 25A
Enclosed - in ground: 16A, 20A, 32A, 40A   *8. You have a very large shed with 20 fluorescent light fittings. Each fitting has 2 x 40 watt tubes & a capacitor fitted. After 2 years, the 10 amp light switch mechanism fails & you wish to buy a replacement. Assume that the supply voltage is 230 volts. What do you buy?* 
Considering that the 10A mechanism failed relatively quickly, look at using industrial switch gear or rewire to use a relay.  Alternatively, separate the lights out in to a number of banks - each with a separate switch.   _9. You have an inquisitive young child who, despite the fact that you have protective covers on the GPO's in his/her room, is still able to remove these covers & stick things into the GPO's. His/her activity has lead to the RCD of that circuit being tripped on numerous occasions, which is somewhat inconvenient (circuit serves more than one room). The RCD protecting the circuit is rated at 30mA. What can you do to; 
a] provide added protection for the child?
b] reduce the inconvenience to others?_ 
a] Replace GPO with a unit fitted with safety shutters 
b] Install the GPO on a separate circuit/RCD.  Could also consider a 5mA or 10mA RCD.   _10. Describe how you would connect 3 x 1.5mm multi-strand wires into a BP connector?_ 
Strip and twist the wires separately.  Twist the three wire together, trim, fold over, insert into the BP connector, check the screw hit flat on cable, check BP connector is secure.  tape up.   *11. Where CAN"T you install a junction box?*  
In inaccessible locations (such as in wall cavities).

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## Vernonv

Most of these have already been answered, so I'll just add a couple of comments.  

> 2. You have just purchased a new electric welder and want to install a power circuit for it. You have 3 spare circuit breaker spaces in your recently installed consumer unit & an existing 32mm underground conduit going from the consumer unit to your shed. The length of the conduit run is 20m & it has 1 x 90 degree bend/elbow in it. The existing conduit contains a 2.5mm 2c+E TPS cable supplying 2 x DGPO's & 2 x 36 watt fluoros. The welder's rating plate says that it is single phase, 230 volt, 50Hz & 15 amps at 100% duty cycle. It will be plugged into a 15 amp outlet. 
> a] What type of PD (protective device) will you use?
> b] What are the ratings of the PD?
> c] What type & size of cable will you use?

  Personally I'd install a sub-main to the shed (pull out existing cable) and setup a new switchboard in there - gives you more scope for expansion.   

> (12) Why do high voltage mains lines have three carriers while low voltage have four?

  Who cares. Why is that even relevant to DIY or even domestic electrical work.  :Doh:

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## chrisp

> Personally I'd install a sub-main to the shed (pull out existing cable) and setup a new switchboard in there - gives you more scope for expansion.

  Vernon, 
Good pickup.  I was going to post a follow up post to my post as after I sent it the same idea occurred to me too, but I took the question literally as an exercise in selecting the cable. 
It maybe quite possible to use the existing cable too (although the voltage drop is getting up a bit) - it would depend upon what the existing GPOs are used for.  In any case, the old 2.5mm2 might be able to be used as a draw wire for a heavier cable. 
With regard to the questions in general, I don't mind this sort of thing being aired as it could be quite educational to all concerned.

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## GraemeCook

> 9.
> You have an inquisitive young child who, despite the fact that you have protective covers on the GPO's in his/her room, is still able to remove these covers & stick things into the GPO's. His/her activity has lead to the RCD of that circuit being tripped on numerous occasions, which is somewhat inconvenient (circuit serves more than one room). The RCD protecting the circuit is rated at 30mA.
> What can you do to; 
> a] provide added protection for the child?
> b] reduce the inconvenience to others? 
> 1) Leave as is and think of it as evolution in action, or
> 2) Remove power point, make the wires safe in their own little BP connectors, tuck in wall, place blank cover where power point used to be.  No power point, no danger.  (if the little $#&@@*!**% wants to break through the plasterboard wall they'll be wishing the RCD hadn't tripped!!!)

  Good response, Master, experience is a great taecher. 
We had the same problem with an inquizative little ****** who regarded the safety plugs in GPO's as a challenge. 
With the old style GPO's where the front plate was held on by two screws, rather than just snapping on, we put in the safety plug, removed the screws, then screwed a thin plastic "retention cap" across the safety plug.   The retention strap was actually a short length of blue package strapping.     
Cheers 
Graeme 
PS: Please, do not tell Nev.

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## Vernonv

> With regard to the questions in general, I don't mind this sort of thing being aired as it could be quite educational to all concerned.

   Couldn't agree more  :2thumbsup: . I certainly feel the intention of the OP is to provoke discussion and to genuinely provide information (which is all good).

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## dambat

> Most of these have already been answered, so I'll just add a couple of comments.   Personally I'd install a sub-main to the shed (pull out existing cable) and setup a new switchboard in there - gives you more scope for expansion. 
> Who cares. Why is that even relevant to DIY or even domestic electrical work.

  The concept of phase to phase polarity is relevant to domestic electrical work.  If you understand that, you understand how three phases can be carried in three carriers.

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## chrisp

> (12) Why do high voltage mains lines have three carriers while low voltage have four?

  The HV system is three-phase three-wire (delta) system whereas the LV is three-phase, four-wire to bring out the star-point as the neutral. 
But more interesting questions is why we use three-phase in the distribution system?  Effectively you can transport three times the energy over three wires than you can with two wires - it saves a hell of a lot of copper. 
And another interesting point.   Have you noticed that really HV lines use multiple conductors for each phase.  For example, next time you see a 500kV line, you will see each phase is made up of four conductors.  You will also notice spacers that are used to keep the four conductors apart in a square formation (even though they are electrically connected together).  Why is this done?  The electric field is one of the "inverse squared" laws - the electric field near the conductor is an inverse function of the radius squared.  i.e. the electric field (V/m) is stronger the closer you are to the conductor. 
 As the potentials of these lines are very high, if the conductor is too small, the electric field near the conductor will be higher than the ionisation potential of air and a corona will form.  Rather than make the diameter of a single conductors larger, it is easier, and cheaper, to use a number of spaced conductors to emulate the electric field around a larger conductor. 
Oh, and why do we use high voltages in the distribution system?   The higher the voltage , the lower the current (for a given power).  The lower the current, the less copper required, and the less I2R losses.

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## elkangorito

So far, almost all replies have been excellent with some great ideas coming forward. I must admit, I've picked up a couple of tips myself. :Shock:  
Great response by Chris...of course, we expect nothing of a lesser standard by him. :2thumbsup:  
It would be great if a few more did the quiz. Any takers?

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## journeyman Mick

> I've put together some questions for DIYers to answer. Please, this is only for non-qualified people (not qualified as an electrician). 
> The object of this test is to assist those who wish to expand their knowledge on electrical DIY. It is in no way intended to ridicule or attack any individual. 
> Please keep answers brief. 
> To other "qualified" posters, please refrain from providing any answers until about 2 weeks from now. I shall not provide any answers until about the 5th of July, however, I will provide further explanation regarding questions prior to this date. 
> Here is the test.    
> Electrical questions for DIYers only.  
> 1.
> When looking at a GPO, which pin is the "active"?  
> 2.
> ...

  
1. top left
2. a,b & c ask my sparky mate next door. Incidentally, I reckon the bend in the conduit might be a problem.
3. yellow + neutral, brown = active, green = earth. Check for leakage between conductors using a megohmeter whilst flexing cable, check for continuity of each conductor.
4.coz the neutral is bonded to earth back at the box and you don't want the earth to be live.
5.use a powerboard with a circuit breaker on it. I can't be bothered doing the maths on the current draw, but if it's over then the breaker on teh board will trip and I'l have to look at getting a gpo put in from another circuit.
6. the wiring of that circuit
7. 
a. 10
b. 15
c. 20
d. 25
8. a standard 10 amp mech
9. a & b either disconnect the bloody powerpoints or screw a cover over them that needs a battery drill to remove :Shock: 
10. strip them, twist together (clockwise) using pliers, snip the end off and insert.
11.anywhere where it's not accesible, although apparently now, inside a plasterboard wall is considered to be accessible. 
Mick

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## elkangorito

Thanks for the contribution Mick.  :Biggrin: 
Most of your answers were very good but two of your answers may need some correction. More info after the 5th of July.

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## Vernonv

> The concept of phase to phase polarity is relevant to domestic electrical work. If you understand that, you understand how three phases can be carried in three carriers.

  Sorry but that sounds like claptrap to me. Read Chrisp's response (which is quite thorough) and tell me again what your original question and this subsequent response has to do with domestic electrical installations.  
Other than the fact that multiple phases are often used in domestic situations, how does the method of high or low voltage transmission have any bearing on their use in domestic situations?

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## chipps

Am a complete novice, so I'd ask for advice in a real situation, anyway here goes  :Roll Eyes (Sarcastic):  
1.
When looking at a GPO, which pin is the "active"?  Bottom pin or is it the earth? 
2.
You have just purchased a new electric welder and want to install a power circuit for it. You have 3 spare circuit breaker spaces in your recently installed consumer unit & an existing 32mm underground conduit going from the consumer unit to your shed. The length of the conduit run is 20m & it has 1 x 90 degree bend/elbow in it. The existing conduit contains a 2.5mm 2c+E TPS cable supplying 2 x DGPO's & 2 x 36 watt fluoros. The welder's rating plate says that it is single phase, 230 volt, 50Hz & 15 amps at 100% duty cycle. It will be plugged into a 15 amp outlet. 
a] What type of PD (protective device) will you use?  One of those portable power point boxes with orange lead, same as builders use? 
b] What are the ratings of the PD?  Don't know what "rating" means 
c] What type & size of cable will you use?  Don't know.  
3.
You have just found a 10m long extension lead in your shed. It appears to be in good condition & does not have a plug or socket connected on either end. The wire colours are yellow, brown & green. 
a] What colours represent active, neutral & earth?  No idea 
b] What tests/checks should be carried out prior to using this lead?  Don't try to fix it, would normally look for alternative use, like stripping the leads & make fishing lures  
4.
Why is the active/neutral "polarity" of GPO's etc important?  Huh?  
5.
You have just purchased components for your new Home Theatre system, which comprises of a DVD player, a 100 watt per channel (RMS audio output power) audio amplifier & a huge plasma screen plus tuner. You also want to use some of your old equipment like a turn table, a cassette player & a CD player (you don't want to wear out your DVD player playing music CD's). In total, you have 7 items (7 plugs) but you only have 1 spare DGPO (double power outlet) in your lounge room. 
a] What can you do in order to safely supply all of this equipment with electricity?  Buy a surge protector power board with heaps of plug holes 
6.
What does a circuit breaker protect?  The wires from the meter box to the spot where the short happens. But not the actual device causing the problem.  
7.
Generally speaking, what is the maximum size circuit breaker used with the following; 
a] 1mm TPS cable.
b] 1.5mm TPS cable.
c] 2.5mm TPS cable.
d] 4mm TPS cable.  Oh I give up, got any questions about 12 volt garden lights???  :Doh:

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## dambat

> Sorry but that sounds like claptrap to me. Read Chrisp's response (which is quite thorough) and tell me again what your original question and this subsequent response has to do with domestic electrical installations.  
> Other than the fact that multiple phases are often used in domestic situations, how does the method of high or low voltage transmission have any bearing on their use in domestic situations?

  Chrisp's answer was good - and interesting.  OK - it's probably not directly relevant, but an understanding of AC theory in general is important if you want to work on it, or even employ someone to work on it.  If you understand delta vs star energy transmission, you're a long way towards a lot of AC theory.  If you think the question is stupid or irrelevant, feel free to ignore it.

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## Vernonv

> If you think the question is stupid or irrelevant, feel free to ignore it.

  I see most people have.  :Biggrin:

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## elkangorito

> Am a complete novice, so I'd ask for advice in a real situation, anyway here goes

  Good on ya for havin a go, Chipps  :2thumbsup: . I'm pretty sure that this thread & certainly this forum may help to enlighten you in the world of electrical DIY.

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## anawanahuanana

Really don't want to be the cause of any drift to what is an excellent thread, but I do have a question related to one of the original ones (about the junction box). My house has a light switch in the family room (inner side of exterior wall) which controls 4 downlights that are fitted under the eaves (cut into the cement sheet) in what is now our pergola area outside (obviously!). They are 240v downlights (I know as I had to change a bulb in one, but don't tell Nev I did it....). Now I had _assumed_ that the active from the switch would run up in the wall cavity into the space in the eaves and go into a junction box which would then feed out 4 seperate actives to the lights. However, the area where this would be is not accessable due to the cathedral ceiling in the room, meaning the only acess to the box would be by removing the eave sheet or unscrewing the relevant roof sheet (Colourbond roof). Assuming again, that this installation has been done to code, would this mean that they should be daisy-chained together much like the lighting circuit actives are at the back of the light switch? If so, I do not believe this to be the case as I removed the assembly when I replaced the bulb and only remember seeing a single cable (3 core) to the light, although will have to pull one out to double check that. 
.....and having just read that, can I also apologise for the almost absurd amount of brackets I have used!
Thanks. 
(I'd answer the questions, but to be honest I'd only have a go at some of those jobs if I had a copy of the standards, which I don't, but again, a good thread) :brava:

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## Vernonv

> If so, I do not believe this to be the case as I removed the assembly when I replaced the bulb and only remember seeing a single cable (3 core) to the light, although will have to pull one out to double check that.

  Could that light have been at the end of the chain? 
Edit: could the junction box (if it exists) be behind one of the other light fittings?

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## anawanahuanana

Perhaps, but the light I had out was the one closest to the switch, so I had guessed not. Also, if there is a junction box up there, it would be down to the installers definition of "accessable" as the lights are mounted in a hole maybe 60mm across, and there is no way you could get your hand in there so to get it out you would need to pull on the wiring (assuming the junction box was small enough to fit through the hole), which is not something that should be encouraged in my opinion.
Thanks for your input though. :2thumbsup:

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## journeyman Mick

> Thanks for the contribution Mick. 
> Most of your answers were very good but two of your answers may need some correction. More info after the 5th of July.

  Only two? Would have thought that there's be more wrong than that. :Rolleyes:  
Mick

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## Terrian

> Perhaps, but the light I had out was the one closest to the switch, so I had guessed not. Also, if there is a junction box up there, it would be down to the installers definition of "accessable" as the lights are mounted in a hole maybe 60mm across, and there is no way you could get your hand in there so to get it out you would need to pull on the wiring (assuming the junction box was small enough to fit through the hole), which is not something that should be encouraged in my opinion.
> Thanks for your input though.

  perhaps no junction box, the lights are wired in series.

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## elkangorito

As promised, I will post the answers on (or immediately after) the 5th of July, so if anybody else would like to "have a go", do so before the abovementioned date.

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## anonymous 21

> I've put together some questions for DIYers to answer. Please, this is only for non-qualified people (not qualified as an electrician). 
> The object of this test is to assist those who wish to expand their knowledge on electrical DIY. It is in no way intended to ridicule or attack any individual. 
> Please keep answers brief. 
> To other "qualified" posters, please refrain from providing any answers until about 2 weeks from now. I shall not provide any answers until about the 5th of July, however, I will provide further explanation regarding questions prior to this date. 
> Here is the test.    
> Electrical questions for DIYers only.  
> 1.
> When looking at a GPO, which pin is the "active"? top left  
> 2.
> ...

  regards nathan

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## Master Splinter

> 10.
> Describe how you would connect 3 x 1.5mm multi-strand wires into a BP connector? strip the 3 wires back,twist and soldar wirers and put in a bp conector, isolate and put a j-box cover over it if needed

  I've only ever seen the earth wires soldered, which I thought was a nice touch - are there any schools of thought on soldering connections???

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## dambat

You're not suppossed to.  The solder can break down and leave the connection loose.  Solder has poor mechanical strength.  Especially in tension, or with vibration.

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## Master Splinter

> You're not suppossed to.  The solder can break down and leave the connection loose.  Solder has poor mechanical strength.  Especially in tension, or with vibration.

  The ones I saw were soldered in addition to the BP connector.

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## elkangorito

Below are the original questions with answers in blue. Of course, there may be other answers that I haven't stated but I've selected the safest known route in my answers.
I'm open to any criticism or suggestions. 
Thanks to all who participated.    
Electrical questions & answers for DIYers only.  
1.
When looking at a GPO, which pin is the "active"?   Left, top.  
2.
You have just purchased a new electric welder and want to install a power circuit for it. You have 3 spare circuit breaker spaces in your recently installed consumer unit & an existing 32mm underground conduit going from the consumer unit to your shed. The length of the conduit run is 20m & it has 1 x 90 degree bend/elbow in it. The existing conduit contains a 2.5mm 2c+E TPS cable supplying 2 x DGPO's & 2 x 36 watt fluoros. The welder's rating plate says that it is single phase, 230 volt, 50Hz & 15 amps at 100% duty cycle. It will be plugged into a 15 amp outlet. 
a] What type of PD (protective device) will you use?
b] What are the ratings of the PD?
c] What type & size of cable will you use?  I thought that the conduit bend would be enough to deter anyone from "doing it themselves" but obviously not. 
If you were to attempt this, there are a couple of solutions;  1] you could use the existing cable as a draw wire & pull in 3 x 4mm "building wire" (single insulated) but by doing so, you must also install a consumer unit within the shed (sub-board). This cable would then need to be protected by a 25 amp (30mA) RCD/CB at the main consumer unit, which should handle the welder's inrush current.
At the shed's consumer unit, you will need two circuit breakers - 1 x 16 amp "Type D" (motor start) for the 15 amp outlet & 1 x 16 amp "Type C" (standard) for the combination light/power circuit (mixed circuit). Both the 15 amp outlet & the mixed circuit will be supplied by 2.5mm cables in the shed. 
2] get an electrician.   
3.
You have just found a 10m long extension lead in your shed. It appears to be in good condition & does not have a plug or socket connected on either end. The wire colours are yellow, brown & green. 
a] What colours represent active, neutral & earth?
b] What tests/checks should be carried out prior to using this lead?    1] Active - brown. Neutral - yellow. Earth - green. The colours may not be "familiar" but brown or red is always "active' when other colours exist.
2] Physically check the cable by running your hands over it's entire length, checking for nicks or deformities. If deformed, the cable should be discarded or the deformed section cut off. Nicks & cuts may be superficial (in no way affecting the internal wires) & may be corrected by applying thick insulative sleeving to the area affected.
Conduct an insulation resistance test from the earth wire to each & every other wire. The voltage for this test should be 500 volts. The result should not be less than 1 Megohm. Ideally, the result should be at least 20 megohms. If less than 1 Megohm, the cable should be discarded.
3] Don't use the cable. Toss it out (after cutting it into unusable pieces) & buy a new lead.    
4.
Why is the active/neutral "polarity" of GPO's etc important?   If the neutral is switched as opposed to the active, internal parts of the equipment will still be live, which can pose a great risk of electrical shock.  
5.
You have just purchased components for your new Home Theatre system, which comprises of a DVD player, a 100 watt per channel (RMS audio output power) audio amplifier & a huge plasma screen plus tuner. You also want to use some of your old equipment like a turn table, a cassette player & a CD player (you don't want to wear out your DVD player playing music CD's). In total, you have 7 items (7 plugs) but you only have 1 spare DGPO (double power outlet) in your lounge room. 
a] What can you do in order to safely supply all of this equipment with electricity?   There are a couple of possibilities.
1] Install more power outlets.
2] Huge plasma screens (& LCD screens) can use large amounts of current. Total up the sum of current used & ascertain whether a power board is applicable. If a power board is applicable, ensure that it conforms to an Australian Standard (I'll assume that appropriate power boards have an Australian Standard stamped on them somewhere). DO NOT purchase (from eBay or the like) power boards from other countries. Do not purchase second-hand power boards.  
6.
What does a circuit breaker protect?  The cable.  
7.
Generally speaking, what is the maximum size circuit breaker used with the following; 
a] 1mm TPS cable.
b] 1.5mm TPS cable.
c] 2.5mm TPS cable.
d] 4mm TPS cable.   Excluding all references to insulation, enclosed cables etc etc;
a] 10 amps.
b] 15 amps.
c] 20 amps.
d] 25 amps.   
8.
You have a very large shed with 20 fluorescent light fittings. Each fitting has 2 x 40 watt tubes & a capacitor fitted. After 2 years, the 10 amp light switch mechanism fails & you wish to buy a replacement. Assume that the supply voltage is 230 volts. What do you buy?   The question is, "What do you buy?"
A large number of fluorescent lights that are power factor corrected (capacitors) will have a significant inrush current. In this case, the item to purchase is a 15 amp (or 20 amp if you want to be super sure) switch mechanism, preferably with silver contacts.
As some people have suggested, the lighting bank could be divided up into smaller banks & then switched individually.  
9.
You have an inquisitive young child who, despite the fact that you have protective covers on the GPO's in his/her room, is still able to remove these covers & stick things into the GPO's. His/her activity has lead to the RCD of that circuit being tripped on numerous occasions, which is somewhat inconvenient (circuit serves more than one room). The RCD protecting the circuit is rated at 30mA.
What can you do to; 
a] provide added protection for the child?
b] reduce the inconvenience to others?   Ahhhh! The contentious question.
Firstly, it would be a good idea if all GPO's were "shutter protected". This would virtually solve the problem.
Secondly, this room could be put on it's own seperate circuit with a 10mA RCD fitted as an extra precaution.
Thirdly, the GPO's could be re-mounted at a height whereby the youngster could not readily interfere with them.
Of course, the GPO's could be removed entirely.  
10.
Describe how you would connect 3 x 1.5mm multi-strand wires into a BP connector?   1] strip each wire in excess of the required stripped length.
2] Identify the "natural" twist if each wire (if it is multi-strand).
3] twist each wire together in the same direction as the "natural" twist of the wire, without tightly gripping them, so that an even twist is created.
4] Insert the twisted wires into the BP connector & ascertain how much copper needs to be cut off in order that minimal bare copper is exposed after tightening the connection.
5] Apply electrical PVC tape over & around the entire BP connector so that there is no likelihood of inadvertent contact with live parts.
NOTES.
The total approximate diameter of the twisted wires should be at least half the inside diameter of the BP connector.
Solder shall not be used. It's illegal for such a connection. 
11.
Where CAN"T you install a junction box?  In any place that is NOT readily accessible. Accessible can mean behind a screwed or latched cover/panel but if this is the case, the cover/panel should be;
a] easily recognised as a "service" cover/panel.
b] should be labelled "electrical connections behind" if it is NOT easily recognised as a "service" cover/panel. 
NOT ACCESSIBLE means in a wall cavity or the like.

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## chrisp

> Below are the original questions with answers in blue. Of course, there may be other answers that I haven't stated but I've selected the safest known route in my answers.
> I'm open to any criticism or suggestions. 
> Thanks to all who participated.

  elkangorito,  *Full marks to you for posting the quiz, and your attitude of educating the masses.*   :2thumbsup:  
I think you have helped show us some of the less obvious aspects of electrical work.  It is important that anyone attempting electrical work should go in with their eyes open. 
Any chance of posting a isolation procedure?  i.e. how one should go about checking a circuit is dead and isolated before touching anything. 
Chris

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## chrisp

> I've only ever seen the earth wires soldered, which I thought was a nice touch - are there any schools of thought on soldering connections???

  In my younger days, I can recall electricians using gas blow torches to solder the earth wires together.  (And when you think about it, they had to use gas as the electricity would be off, wouldn't it  :Smilie:  ).  It was a requirement to solder the earths back in those days. 
It does make me wonder how the active and neutral in the cable stood up to the soldering?  The earth wires weren't insulated back then, the earth wire was bare copper placed between the active and neutral and the whole lot sheathed together.  I wonder how times the hot (from soldering) earth wire melted in to the active or neutral wires? 
Back to your question.  My view is that solder connections are quite good in themselves.  However, there are some issues to be aware of.  The soldering is good for the actual joints solder together (such as wire to wire), but it is hopeless for subsequent pressure/clamping joints (such as soldered joint, or tinned wire, in a screw connector) as the solder slowly "flows" under pressure and the joint looses tension. 
My view, from experience, is either solder the whole joint, or don't solder at all.  Mixing soldering with any form of pressure joint is asking for trouble.   
I've learnt the hard way that it is NOT a good idea to tin wires and then place the tinned wires in screw connections (such as a three pin plug).  The connections will work loose in time.  :Eek:

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## elkangorito

> elkangorito,  *Full marks to you for posting the quiz, and your attitude of educating the masses.*   
> I think you have helped show us some of the less obvious aspects of electrical work.  It is important that anyone attempting electrical work should go in with their eyes open.  *Any chance of posting a isolation procedure?  i.e. how one should go about checking a circuit is dead and isolated before touching anything.* 
> Chris

  Thanks Chris  :Biggrin: .
As for isolation procedures, I'm sure you would have ideas similar to mine. Sounds interesting though. I'll give it some thought.   

> In my younger days, I can recall electricians using gas blow torches to solder the earth wires together.  (And when you think about it, they had to use gas as the electricity would be off, wouldn't it  ).  It was a requirement to solder the earths back in those days. 
> It does make me wonder how the active and neutral in the cable stood up to the soldering?  The earth wires weren't insulated back then, the earth wire was bare copper placed between the active and neutral and the whole lot sheathed together.  I wonder how times the hot (from soldering) earth wire melted in to the active or neutral wires? 
> Back to your question.  My view is that solder connections are quite good in themselves.  However, there are some issues to be aware of.  The soldering is good for the actual joints solder together (such as wire to wire), but it is hopeless for subsequent pressure/clamping joints (such as soldered joint, or tinned wire, in a screw connector) as the solder slowly "flows" under pressure and the joint looses tension.  *My view, from experience, is either solder the whole joint, or don't solder at all.  Mixing soldering with any form of pressure joint is asking for trouble. *  
> I've learnt the hard way that it is NOT a good idea to tin wires and then place the tinned wires in screw connections (such as a three pin plug).  The connections will work loose in time.

  Actually, AS3000 indicates very restricted uses for soldered joints.
3.7.2.5 Retention of stranded conductors.
3.7.2.7 Soldered connections.
3.7.2.11 Earthing conductors. 
My advice is DO NOT USE soldered connections of ANY wire. This covers all bases.  
I think now would be a great time for any discussion about the quiz questions or answers. 
Again, thanks to all who participated  :2thumbsup: .

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## Master Splinter

Thanks for the info on soldering.  Much appreciated. 
For those looking for more info on wiring, codes of practice, standards and so on, it's amazing what comes up when you google for "aus electrical and telecommunication rules"

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## elkangorito

Standby for Part 2 of Electrical DIY questions...coming soon (a week or so).

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## 08yannch

I have not read the answers below and im posting my answer just so when I read the below I dont cheat :P  1. I would consider all 3 pins as live until tested but the active pin should be on the left hand side (when looking at the front of a socket). 2. 16A MCB, hmmm 6mm 3 core wire, and a 15A switch and socket. 3. green = earth, Brown = positive, Yellow = negative. And to test I would with my multimeter check continuity of the wires and check for leeks and do a visual inspection. 4. well it doesnt really make a big deal if its wired the wrong way all it means is when earthed the RCD should trip. 5. one socket for the TV and another socket for a power board for the other stuff should be ok. But I cant be 100% because I dont know the specs of the kit so another DGPO may need to be installed but I would say not. 6. when a circuit draws more current than the circuit breaker it trips blocking power from the circuit. 7. I have no idea. 8. I would fit one of throws 15A industrial switches in they just look and feel so much better. 9. install 10ma RCD sockets and remove all objects that can fit in the plug from the room. And install a switch out of reach of the kid that controls the power point so they can all be turned off when a adult is not in the room. 10. Strip all 3, twist the ends together, fold, tape together (I prefer shrink sleeve, insert, tighten the screw and check for loose strands of wire, if so pull it out and fix. 11. in a inaccessible location.

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## Bobthebuilderer

Out of curiosity can you use a double BP for all connections? As this would be safer?

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