# Forum Home Renovation Electrical  Cable size for power points

## Starky

Wondering what size cable people with steel framed houses use for power circuits. Conduit used and insulation. Just double checking.

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## rebuildr86

haha you are brave putting that question on here, internet forum is not a place to ask a dangerous question like this. pl will scold you for it.
this is exactly why iust is illegal to do your own electrical work .
Now you may be clever, but this post will be shut down by a moderator due to safety risks.
Sorry, i hope you can find an affordable sparky.
Im in Perth, and can recomend some who dont screw u to the ground if you would like.
PM me.

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## Bros

Easy answer and it is not secret squirrel stuff. Cable size is 2.5mm twin and earth.

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## rebuildr86

well now he will go to bunnings and buy it and do it himself.
i think we should show some responsibility and discourage it whenever we can.
Im all for DIY light switch replacement and batten replacement, even tho the law prohibits it, but this potentially shows the OP is trying to do the job propperly, which is sometimes more dangerous than a shonky DIY job as its not as obvious to the next licenced electrician in there.

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## rebuildr86

i guess u may be trying to double check ur electricians work tho?

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## Bros

> well now he will go to bunnings and buy it and do it himself.

  He may or he may not but if you think that knowing the size of cable to do this or that is enough think again. 
Knowledge like this is quite legitimate to give and has been given many many times before and will still be given but the fine details of how to do the job like terminating will not. 
It is better keeping DIY's in the tent than driving them outside as you can help them understand what is being done than getting this information which is readily available on the net without any guidance.

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## rebuildr86

> He may or he may not but if you think that knowing the size of cable to do this or that is enough think again.
> .

  exactly my point.
it worries me that someone is asking the question on the net thinking that,  "armed with this information, i can do it"

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## Bros

> exactly my point.
> it worries me that someone is asking the question on the net thinking that,  "armed with this information, i can do it"

  He'll find out different.

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## chrisp

I’m pleased with the approach shown by Bros. I do think that when one is informed, one tends to make better decisions and hopefully know when they are getting out of their depth. 
Cable rating also depends upon the installation method, so it isn’t a one size-does-all thing. The cable rating tables are readily available with a quick search of the web - https://www.olex.com.au/eservice/Aus...%20V3%20LR.pdf 
I think it is good if people understand that changing the conditions around the cable has an impact on its rating. e.g. check the table to see what happens if the wall is subsequently insulated with loose fill insulation and the cable with originally hanging loose in the wall cavity.

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## Bros

> I’m pleased with the approach shown by Bros. I do think that when one is informed, one tends to make better decisions and hopefully know when they are getting out of their depth.

   It's always been my approach on broad based questions like this.

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## Marc

I think you should buy 4mm2 to be on the safe side.  :Smilie:

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## cyclic

> I think you should buy 4mm2 to be on the safe side.

  Being knowledgeable as you are, would you recommend Infinity brand as a good brand of cable to purchase ??

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## Marc

From the name it seems they would last a long time .. an infinity!
And since that brand is so good, you only need 1.5mm. Quality is all it matters  :Smilie:

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## cyclic

> From the name it seems they would last a long time .. an infinity!
> And since that brand is so good, you only need 1.5mm. Quality is all it matters

  Yea, really good cable https://www.accc.gov.au/update/infin...e-its-too-late

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## rebuildr86

well guess i see where ur coming from. i just cant change my mind on recommending the op gets a qualified sparky in to install everything to code.

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## commodorenut

A quick google search generally provides most of the answers that a "wannahavago" DIY would ask on here. 
By not answering someone - they'll simply find the answer elsewhere, and we all know the internet is 100% true right? 
I think someone asking the question on here should be given a legitimate answer - like above where they were told 2.5mm, as it's readily available info. 
But as for asking for more in depth stuff, such as "how do I wire up a light switch when there's 3 wires behind it?" - that's definitely one that should be answered with a "there's 3 wires as it has a loop, and if you get them in the wrong order, you'll either have something that doesn't work (prompting more dangerous exposure to 240V to check why) or you may even short the circuit if there's both A&N looping at the switches - which at a minimum should blow a fuse or trip a breaker - but if someone has screwed around it may not - and it could start a fire in behind the architrave - hence you really need to get a sparky onto it" - which neither gives a "how to" nor does it denigrate the OP - it can point them in the right direction and make them think about the consequences of not following that advice.

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## DavoSyd

Guys, he's just double checking by asking here... Clearly he already knows the answer...

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## Starky

Thank you for the responses all. Electrical work was completed awhile ago but was questioned by a sparky friend (industrial).

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## Moondog55

I took the question to ask what is best practice myself, standard house wiring is minimum standard and not IMO "Best practice"
If I was doing another house from scratch I certainly wouldn't be using standard wiring again, I would use commercial practice and 4mm wire and use multiple sub-boards depending on the size of the house and outbuildings
There is no disadvantage in going oversized except for a small extra capital cost, even if the government and power companies cheat by limiting supply current

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## Bros

> There is no disadvantage in going oversized except for a small extra capital cost, even if the government and power companies cheat by limiting supply current

   Actually there are disadvantages as it would be difficult to terminate more then one 4mm cable in a GPO as they are not designed for that. Going for overkill is just a total waste of money.

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## Moondog55

I've seen dozens of commercial installations done in kitchens and the usual practice of the sparkies who did the work was to always use a junction box for the take off, it allowed us to use a 15A power points without running separate circuits and most commercial gear runs off 15A points even when they don't pull more than 10A usually

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## phild01

But how many homes need that level of capacity, and then if they do, have dedicated circuits.

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## Moondog55

I think we are in a minority of one here but only one sub board so far as the out buildings are not done

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## Marc

The debate between electrician and owner on the size of the cable to use in an installation never ceases to amaze me. 
It is true that wiring a house with 4mm2 instead of 2.5mm2 may seem like a waste. However ... it is the owner who pays for the cable and the reasons behind overkill in the mind of the owner may well be that he has potential added loads in mind he does not want to discuss at this time.
A classic one is the scoffing from the electrician at a sub board request in a shed or at an upgrade from 4 to 6mm cable in a 3 phase installation.
By the way ...
I mentioned 4mm cable as a joke further up, and I understand the difficulties of using it in an ordinary powerpoint  :Smilie:

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## Bros

> The debate between electrician and owner on the size of the cable to use in an installation never ceases to amaze me. 
> It is true that wiring a house with 4mm2 instead of 2.5mm2 may seem like a waste. However ... it is the owner who pays for the cable and the reasons behind overkill in the mind of the owner may well be that he has potential added loads in mind he does not want to discuss at this time.
> A classic one is the scoffing from the electrician at a sub board request in a shed or at an upgrade from 4 to 6mm cable in a 3 phase installation.

  I dont believe there is any debate but the person wanting the job done should get his house in order first and specify exactly what they want so all can quote accordingly. I believe it would be rare for an electrician to encounter a non standard installation like this and would try and talk the owner to a standard installation. The reason being the cost increase could be considerable and he may get a fright when the first quote came in and then deal with someone else for a standard install and the first electrician loses the job.
However if the owner did a good job with the spec and included the service upgrade it could be expected that they may wish to accept the price difference so it would depend on the owner.
Some electricians will go a bit above standard on jobs if it doesn't cost much extra. Then there is the quality of fittings and this varies considerably including the price.
Two weeks ago I was at a friend place in central west Queensland wiring up a shed for him. I don't have a contractors licence so I talked to the local contractor and it was OK from him if i do the job as it suited him as it was 80klm out of town over a dirt road and he wanted to only be there for a day and the shed job would be well more than a day as he had to dig a 60M trench for the submains. Now that aside I said I was going to put in a 8 module subboard (which was big enough) and he said don't bother put in a 12 module as there is not much difference in price.
So some electricians take it on themselves to go above standard on jobs.

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## Marc

Yes, I actually expect an electrician or any trade to push the standard a bit up, not down. My electrician on the other hand, seems to be some sort of wiring socialist and always keeps things on the very edge, stretching it to the max ... even quoting older standards saying if it was good then why not now ... and stuff like that. Goes completely agains the grain with me. I say if 4mm is minimum standard, I want 6mm.  :Smilie: 
Must be the blacksmith in me. If something needs to be 50x12, let's do it 2"x1/2"  :Rofl5:

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## Brian7886

> The debate between electrician and owner on the size of the cable to use in an installation never ceases to amaze me. 
> It is true that wiring a house with 4mm2 instead of 2.5mm2 may seem like a waste. However ... it is the owner who pays for the cable and the reasons behind overkill in the mind of the owner may well be that he has potential added loads in mind he does not want to discuss at this time.
> A classic one is the scoffing from the electrician at a sub board request in a shed or at an upgrade from 4 to 6mm cable in a 3 phase installation.
> By the way ...
> I mentioned 4mm cable as a joke further up, and I understand the difficulties of using it in an ordinary powerpoint

  Funny u say that, its usually the opposite for me, home owners scoffing when you tell them they NEED to upgrade the size of a circuit or something.  
as we all know 2.5mm is the typical power circuit size, but thats not taking into consideration a....what protective device is or will be used, how long the final point of the circuit is (ie how much cable in the circuit.....this can lead to too much voltage drop and thats where cable sizing needs to change), what the installation is actually like. All those things work hand in hand.  
So yeah, we can tell him 2.5 but we dont know for sure if thats suitable for his specific installation, even though it probably is

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