Thread: Q for sparkies - new supply

Originally Posted by pibby

..... The split phase is treated as 415v and allows approx half the size cable? How many cables in total? .....

Cheers.

Not 415V. It will be 480V.
3 cables involved.
240V(1)-Neutral-240V(2)

There are two phases here. The first is taked from 240V(1)-Neutral and the second from Neutral-240V(2). These two phases will be distributed around your house so that the load between the phases is approximately equal.

The 480V for your shed is taken by wiring between 240V(1) and 240V(2).

My dad had this arrangement on his property. In his case, the supply authority placed the pole with the transformer ~20m from the house. This was in the 1970's, so regulations may have changed since then and state regulations probably vary. I also recall it cost him a packet to have it done!

Split phase can get you an effective 480v supply. Think industrial single phase 415

It can also give you two phases of 240v.

It's done because it's cheaper to run any distance and then put a transformer in for standard domestic.

You can't get three phase from it.

No, you can't put you own pole in but that only counts for the first pole from the transformer of if the transformer is on a plow on your property the pole the transformer is on. After the fuses as long as you run to code you should be Apple's

Not that you probably couldnt do it better than the mob that will get paid a mortza to do it, you just can't sign the bit of paper because your not qualified.

Your mialage on this info may vary. Its lunch time and i just asked the sparky whose car I'm doing the timing on*.

Pibby, what are you trying to achieve by having a pole?
Put it all underground, get it all out of site, less damage can occur then.

Originally Posted by Vern

Pibby, what are you trying to achieve by having a pole?
Put it all underground, get it all out of site, less damage can occur then.

Vern - trying to understand if I can get an additional span in above ground to reduce the underground sizing/distance. When I checked the sizing last time for 240v using 10% voltage drop I was comfortably able to drop a cable size if I got it down to say 280m. Without doing the $calcs I was trying to understand if I could put a pole in and if so I would then check the $ equation. If I had to pay someone I wouldn't consider it. Now it's going to be this split phase 480v I'm trying to understand what it does to the cable sizing too.

I am not sure if I'm being sold a pup with the solution the power company and the sparky have put together as adjacent to my entrance is a house which the sparky and the guy at the power company seem to be doing everything to look after their interests with the placement of the pole, I know the sparky has done work for them before but not me.

The entrance to my block is 20 metres at the road then 250 metres deep where it has opened to 30 metre wide. By this stage the forest starts, before that it is pasture. I'm then another 180 acres of forest behind this so I don't want overhead anywhere near that but I don't have a problem for the start of my entrance.

No more than 5% volt drop.
They will only supply power TO your property, from there on its your problem.
480 (2 phase), you can reduce the cable size as you are spreading the load over two phases.
Are the cables to be dressed up the pole, or are they putting a pit in for you?
Run it in aluminium as I stated earlier to reduce costs (about 60% cheaper in cable cost), as I said, from past jobs I've done, I'm guessing 120mm2 .

What cross sectional area cable have you been doing your calculations with?
Aaron

GenCalc says 120mm2 copper or 185mm2 Al for 100 amps at 280m.

Let me know if you want other crap calculated.

Dunno what this two phase poo is, must be a rural thing? I have never heard of '480v' and our countries share mostly the same rules

Also something to consider is the power company may charge you extra each month for having three phases over the normal two.

As others have said, get another sparky. Something there doesn't seem right.

Originally Posted by BadCo.

GenCalc says 120mm2 copper or 185mm2 Al for 100 amps at 280m.

Let me know if you want other crap calculated.

Dunno what this two phase poo is, must be a rural thing? I have never heard of '480v' and our countries share mostly the same rules

Also something to consider is the power company may charge you extra each month for having three phases over the normal two.

As others have said, get another sparky. Something there doesn't seem right.

Your calcs are for single phase, my guesstimate is split over two phases, if running two phase, who is going to use 100a per phase? Split the load.
Yes its a rural thing, he will have a swer line I presume, they can take a second tap from the transformer to produce 2x 240v, or he has a 2 phase transformer across the road.