Electric cable standard - 2.5 mm2 twin & earth cable enough?

Hi all

Building a house at the moment and just finished electrical wiring. When I inspected the house on last weekend, I noticed the electric cables for lighting and powerpoints are using 2.5 mm2 twin & earth cable (2.5mm2 x 2c+e).

Not sure whether this is sufficient to support all downlights and powperpoints (there are about total 45 downlights and 25 powerpoints through the house).

Also, should the kitchen applicance (e.g. canopy, oven, microoven, dishwasher and cooktop) using different size cable, say 4mm2 twin & earth cable? or 2.5mm2 twin & earth cable is enough?

What is the Australian standard for the electric cable that builder should use?

Thanks heaps

Min sizes
power 2.5mm up to 12 double points per circuit
lights 1.0mm
separate electric oven 4.0mm

thanks cherub, so which means builder need to use 4mm electric cable for majority of kitchen applicance, right?

What about ducted heating and cooling system? Is it work on 2.5mm electric cable or some larger size cable?

This isn't something you need to really worry about.

Electrical is the most highly regulated and inspected trade. Telling the difference between a 2.5mm and a 4mm can be difficult for someone who isn't in the trade.

Depending on the cable installation conditions 2.5mm2 can be sufficient for an oven, as long as it is installed correctly and the rating of the oven is taken into consideration, but most importantly the rating of the breaker will be matched to the cable.

If you have concerns speak to your builder.

the other posters here are NOT electricians... read below.

there is NO magic cable size that is dictated to builders or electricians to be used for specific jobs. In fact a builder has nothing to do with anything electrical... other than deciding on where things are placed and adding 30% ontop of our rates
cable sizes and circuits are all decided in planning stage by the electrician or electrical engineers. They are decided on a multitude of factors !! in fact there are 3 books with hundreds of pages that we need to know inside and out to determine cable sizes their effects, and effects on the cables themselves due to other factors. I wont go into details because it will sound like an overseas language... BUT heres a basic rundown, hopefully it will enlighten you to trust your electrician... he has done 4 years worth of schooling with MAANY regulation tests and MANY years in the field so you can have your lights switch on and power for your toaster.

you can have UNLIMITED powerpoints on a circuit of 2.5mm cable as per australian standards and regs..
the reason why they are split up is because of convienence when a fault occurs, i.e you dont want ALL of the house powerpoints turning off in the event of an appliance fault.. this too is mentioned in our regulations and standards.
i.e. i run 10-15 gpos per circuit, others do 20-25, i know a sparky that does 5 per circuit!it all depends.

an oven feed in 80% of volume builder estate homes are wired in 2.5. this is because the ovens supplied dont warrant the need for a large cable type, there is also cable run lengths taken into consideration that MIGHT make the cable bigger to accomodate voltage drop.. but this is rare in an estate house..
so what dictates an oven cable size is: length of the run of cable, current draw of the oven, characteristics in which the cable is run, i.e. enviroment, thermal effects, insulation etc etc etc i wont go into details this is electrician talk , there is no ' standard ' one size fits all.

1.0mm and 1.5mm are the most common sized cable for light circuits , depending on the electrician/job. not every single light in the house is on the one run of cable. This too is split up to accomodate different load types, number of lights, fault convienence, fault loop impedeance etc etc etc..

also you question regarding the appliances... there are all ran in the same type of wire as the other powerpoints ( 2.5mm ).. again depending on how the electrician wired it, dictates how he/she has split their circuits up.
there is no reason to run 4mm for general purpose outlets, ( and you wouldnt get 2 x 4mm cables into a powerpoint! ) this sized cable can supply up to 32amps ( give or take depending on cable runs, external effects etc )
mainly ran for LARGE air conditioners, swimming pool gear, VERY long runs of cable, induction cooktops, large double ovens, other specific equipment.

i hope this shed some light, basically all you need to worry about is do the lights turn on? is there power at the powerpoints? and i safe to use this equipment?
dont fret over cable sizes.. your sparky will know exactly what they are doing

My "A" Grade electrical license begs to differ.

What parts of Cene's post do you disagree with Charger? I am an Electrical trades also (although now drive a 500MW generator), and cant see any issues. I agree that unless people wish to read both AS3000 and AS3008 then they have no choice but to go with the guidance of the Electrician.

Unless you have been physically involved in the trade over the last five years you wont even be able to identify the TPS T&E. Old 2.5mm is about the same size as new 4mm, and new 2.5 is like old 1.5mm.

The best and worst of these forums is the amateur input. I always appreciate if an "expert" can put some creds at the bottom of the post. So thanks Cene .

This is like asking your greengrocer if his fruit is fresh

I disagree with the part where he says the other posters are not electricians. I am a qualified electrical mechanic with a fitters endorsement and the electrical nominee for the electrical contracting company I manage. I have worked as an electrician all of my life.

If you read my post I said the exact same things he did, just without all of the hyperbole.

Hows that for your amateur input?

[
I disagree with the part where he says the other posters are not electricians. I am a qualified electrical mechanic with a fitters endorsement and the electrical nominee for the electrical contracting company I manage. I have worked as an electrician all of my life.

If you read my post I said the exact same things he did, just without all of the hyperbole.

Hows that for your amateur input?[/quote]


I think maybe you are being overly sensitive Charger. The point is that there is a lot of unqualified advice given on the forum - sometimes good, sometimes not. If you are thrashing around paint colours, facade detail, then all is good. Otherwise, unqualified information can confuse the issue.

Cene's post probably had the detail that the original poster desired

Hi, sorry to those i assumed that were not electricians, i didnt mean to generalize..

Anyway... ume homes how is your house electrical going?

cenemelectrical [quote][/quote] "your sparky will know exactly what they are doing"

hmm, you have a lot of faith in all licenced sparkys in Oz.

Even if they do know what they are doing, they still maybe acting negligently as apposed to being incompetent.

Often its not just about the regs to follow.

New cable is fairly easy to see the sizing.

I'm just not a trusting person by nature.

Anyway I think the cable size has been answered.

If you like to read the AS3000 look around online should find a free copy.

Cheers

Pulpo

I found I had to get my sparky to go a size up on a few cables to 'future proof' myself and run a few extra circuits to/from the circuit board.
Eg,
Bigger oven down the track,
Pool equipment needing more power,
A/C needing more power, (ended up running 3 phase)
Spa hot pumps in ensuite needing more power,
Being able to weld in my garage down the track, (dedicated circuit)
Induction cook top provision(some up to 42 Amp!)
Oven dedicated 32Amp circuit
Separate circuits in each side of kitchen (went through all the crap I have with sparky in kitchen appliances and what is posssible to be on at same time and too much)

Cable cheap to throw in before the plaster goes on.
I put power points in locations so the cable runs ended up in pretty much every wall.
Makes adding power points down the track easy.
Food for thought.

And this is why you get the electrician to do the work, but you get involved in what is happening. So education is good.

While I appreciate this is thread is somewhat old, I'd suggest people factor is use and load rather than cable size.

In the kitchen, most people will use a kettle (many of these are 2400W) and most laundry's will have a dryer (one I checked is rated at 8 amps). Put these on the same 16A circuit which is what most 2.5mm2 2C+E TPS is rated at (other than free air) and You now have 18Amps being drawn and the circuit breaker is likely to trip.

So if you want to be able to use your kettle and dryer at the same time - ie have a hot coffee/tea, then you may want to ensure that the laundry and kitchen are on separate circuits.

A higher capacity circuit typically wouldn't be used for domestic appliances because of the impact of a fault - do you really want to give your kettle that normally uses 10A, 30A or more in a fault situation ?

Also this is why fridges are often on their own circuit - lets say a fault in a tv trips the breaker while you are away; most people don't like coming home to a (semi) defrosted fridge when they've been out for a few hours - if you are away for a week and the situation is even worse.

Moving on to ovens some use 3100W and some use 5-6000W ... A 3100W may work with 2.5mm2 2C+E; however some people prefer to use 4mm2 as the oven is expected to draw a high current for extended periods of time (unlike a kettle). Obviously a 6kW oven, drawing 25A is going to require thicker wire than 2.5mm2. So I'd check the manufacturers guide for the oven.

As for lighting - there are a number of standards surrounding drops, however don't exceed the load - 45 x 50w globes are 2250w or less than 10A; 45 x 100w globes are 4500w or 18.75A.

As for power points - again, think of use and how many you want to use at once and what for - many domestic appliances and lamps don't use a lot of power, so don't need separate circuits. And every separate circuit will cost; this "cost" is much cheaper at build time than afterwards; however overloading circuits and risking a fire is something most people would prefer to avoid ... especially after the fire.

Most electricians if you talk to them about what you are doing are pretty good; and if needed get specialist advice.

Glad to find this thread. I need advice on this subject.

I have just purchased a 40 amp plasma cutter, for hobby use I guess you would say. Now I also need to get some clarification about this. How do I determine if the wiring in my flat can handle 40 amps ? Obviously just changing the gauge of the fuse wire would be dangerous if the wiring is not rated to handle at least 40 amps.

I suppose I will need to call in an electrician to get a reliable answer based on examining my wiring and fuse box.

Where are the relevant electrical building standards available ?

Thanks for any advice you can provide.

All good advice above.
It's good to see some licenced sparkies chiming in to this forum with their views.
As per above. I use a 40 -140amp stick welder at home off a 15amp circuit.
How does that work ???

Stewie ( definiely a non-sparky )

Are you talking about a 15amp circuit breaker or 15amp gpo ?

A 15amp circuit breaker is usually a 16amp cb, and 2.5mm twin and earth.

A 15A gpo is usually on 4mm twin and earth with a 20A CB.

The current output from your welder is at a lower voltage, so the welder is consuming less than 15A on the 240v side.

Seen in some USA HT forums, the need for 110v 20A powerpoints for their power amps, where over here the same amp (dual voltage transformers inside) can be plugged straight in to a standard 230v 15A powerpoint.... the lower the voltage needs greater current draw.

<standard disclaimer> I am not a sparky !

With welders / cutters, the current rating of 40A or 140A is about the current on the output of the welder. This is much higher than the input current. The reason it doesn't draw this much current is that it can use a transformer (or equivalent alternative) to transform the voltage and current. A 10:1 transformer can take 240V at 10A and produce 24V at 100A. In both case it is the same amount of power.

So to see if your wiring can handle a device, you need to look at the input power draw, which should be on the labelling. If it has a standard 10A plug, this should be less than 10A.

Thanks guys. Yeah it is a 15amp GPO. I knew that bloke Ohm would have his hand in there somewhere with some magickery.

Stewie