Thread: Electricity Mains

Try contacting your local electricity supply board. They may have some sort of record of what the supply to your property is rated at.

Came home from hols in Qld at the end of January, expecting to see the gorund work for our extension well under way. Turned into the driveway to see that the plumber had manged to dig up the underground power with his back-hoe! We waited 3 days for the electrician and the Powercor guys to get their act together to repair the break and give us sparks again.

The sparky said we were lucky to not have had to upgrade the power supply to the house. The underground power went in about 20 years ago - house is over 100 metres from the street - when 90 amps waas the required current for houses (and the legal one). Sparky said that we may have to upgrade to the new 120 amp supply, but we escaped that monumental expense thankfully.

So the short story according to our electrician - 90 amps was the standard until relatively recently, but is now 120 amps. If your home is relatively old then I bet you have a 90 amp supply. You can get this checked - they test the current and voltage at the pole end, then check the same at the meter end. If there is a significant drop off you may be in for an upgrade.

Hope this helps - have to say that getting our new bit added has helped me pick one hell of a lot of info - some of it useful.

Cheers, and may you be drenched in dihydrogen monoxide but not while you are fiddling witrh the power.
Jeff

Woodbutcher - our holiday to qld was actually largely spent in Toowoomba - probably saw you a dozen times! But of course would not have recognised you.
Jeff

Pity we didn't know. There is a few of us up here that would've organised some sort of gathering. Oh well next time

It'll be printed on the mains box if you've got overhead power, if you've got underground it'll be marked on the main fuse at the meter panel.

Woodsprite - dunno bout country vic, but be damned if 90amps is a standard in the "burbs" 80amps is the upgrade from old 35amp and up.

Sounds like you're sparky may have been referring to the current capacity of the cable so you at least get a nominal amount at the end of such a long run.

houses built in about the last 15years will have a maxium demand of 100amps. this is because of your "mains cable", 95% of the time its 16mm2 copper in 2 wires, a red inner insulation and also a black one.

Overhead supply 99% of the time is 25mm2 ALUMINUIM. max demand of 100amps.

underground in 99% 16mm2 copper connected to a 185mm2 ally 4core conductor.

houses built earlier depends on the installation of the house.
most have 6mms mains and have a max demand of 55amps.

small houses/units/older houses with 6mm mains run on a 50/55amp fuse depending upon the mains box on the house facia or the meter position if you have underground power.

otherwise you will have an 80amp fuse.

if like alot of houses now and run 1,2,3 split systems, air cons, welders you will have a 100amp fuse.

the electricity meters are not designed to run over 100amps.
if a customer requires more power you will need to upgrade mains cable, install private pillers, upgrade main switches and run "CT" metering which changes the reading of the meters so it can read your useage.

or, you could always pay for a transformer out the front of your house!

Enjoy

Hi, I (am hijacking) was reading through this thread, and was wondering what the mains supply (overhead) should be in South Australia. i had a sparkie come and check over the house last year to see what needed to be upgraded, and his eyes nearly popped out when he saw I still had the 1952 meter box, rated at 40 amps.
Who is responsible for the cable from the pole to my house, is that AGL's or mine when the bill comes in?

Hi Tameriska - I had ours upgraded last year due to installing ducted reverse cycle aircon (I am in SA), the house was built in 1953 so everything electrical would probably be the same as yours - 40 amp incoming supply to a meter and fusepanel located inside the house.

ETSA did the upgrade from 40 to 80 amps at no cost to us !

We also took the opportunity to move the meters to an outside box - it was a real pain having to let the meter reader in every six months or so. We had to pay a sparkie to do that part though. I took the opportunity to get the fusepanel upgraded also.

Give AGL a call, they were very helpful in my case.

Thankyou for that BigJim. I am waiting for the sparkie to turn up, he was pretty flat out at the time he came round and had a look.
I am lucky, the meter box is outside, old wooden fuse box on the back porch'
Did you have to have the house rewired or was it just upgrades?

Yes, I decided to have the house rewired at the same time due to 50's rubber wiring that had gone all crumbly.

It's amazing how many other side projects get put in front of having aircon put in.
I still have to install the insulation in the ceiling...

You may not have to rewire if your wiring is still OK, but being a 50's house, I suspect you are in the same boat.

Originally Posted by teza

houses built in about the last 15years will have a maxium demand of 100amps. this is because of your "mains cable", 95% of the time its 16mm2 copper in 2 wires, a red inner insulation and also a black one.

Overhead supply 99% of the time is 25mm2 ALUMINUIM. max demand of 100amps.

underground in 99% 16mm2 copper connected to a 185mm2 ally 4core conductor.

houses built earlier depends on the installation of the house.
most have 6mms mains and have a max demand of 55amps.

small houses/units/older houses with 6mm mains run on a 50/55amp fuse depending upon the mains box on the house facia or the meter position if you have underground power.

otherwise you will have an 80amp fuse.

if like alot of houses now and run 1,2,3 split systems, air cons, welders you will have a 100amp fuse.

the electricity meters are not designed to run over 100amps.
if a customer requires more power you will need to upgrade mains cable, install private pillers, upgrade main switches and run "CT" metering which changes the reading of the meters so it can read your useage.

or, you could always pay for a transformer out the front of your house!

Enjoy

OKay, when I was house bashing in Perth bout 7 years ago, all standard sizes houses where getting 10mm2 mains underground in flat orange sheath with 80amp main breakers. I'm pretty sure that 10mm2 can handle 80amps with ease so maybe 16mm2 is overkill or just allowing for future extras (or larger air-cons)

Just a thought

Hello,

Most people start talking about updating their mains when they have just purchased some electrical appliances and most often power hungry air-conditioners. I am an electrical engineer so you can rest assured that the information I post is accurate.

Well on older style houses you'll find 4mm mains cables which have a rated capacity of 32A, this was more than sufficient in the 'old' days for running lights and power points. Though most people are replacing their gas oven/stove and hot water service with electric counterparts which have a significant demand in terms of raw current drawn.

Ok enough of the history lesson, strickly speaking 4mm cable might be enough if the total current you draw is less than 32A, though with two air-conditioners totalling 14 kW and normal household power its unlikely that 4mm will do (maybe it might just make it, if you dont have electric oven/hot water service).

So the current standard is 16mm cable which is rated at 80A, that should be more the sufficient for the normal domestic household (i.e. electric oven, hot water service & air-conditioners totalling 14 kW)

Now, if for some unusual reason you need to draw more current, possibly because you want to at some stage install a whole-house ducted air-conditioner and maybe additional high load appliances, then you can use 25mm cable which is rated at 100A - This is the highest thickness power cable which you can use for SINGLE PHASE POWER.

If you want to draw more than 100A, then you will have to switch to 3-phase power which has an RMS voltage of 415V. Though these days this is highly unlikely unless you want a ~25kW air-con which runs only on 3-phase power.

Anyway bottom line is that all these are single phase options.
4mm -> 32A
16mm -> 80A [should be enough]
25mm -> 100A [ high demand applications]

Hope this sheds some light on the issue.

Regards,
Anthony

Anthony You are almost right

Current carrying capacity depends on a few factors

How its run (underground.overhead,in conduit. Buried direct etc)
Type of cable (Single core, 2 core,V75 V90 etc)
What its run with etc
We use AS/NZ3008 to determine this.

Also in all my years as a Sparkie Ive never seen 4mm2 Mains
Nor have I seen 25mm2 Mains in a domestic environment.

I'm no sparkie but I do know that when I was getting my mains installed, some I spoke to said 10mm2 was sufficient which technically maybe the case, I cannot understand why people would not have 16mm2 3-phase installed on the off-chance they may require it down the track? For me it was only $100 difference (Cost of the cable/breaker) between 16mm2 single phase and 3-phase. No brainer really...