Electrical cable to the new shed. Sparkies?

**Redgy** · 11th January 2006, 06:46 AM

I had a quick look through the book at 10mm2 (plenty of current capability) cable using one of the tables that says it has a volt drop of 3.59 mv/am (Vc) the formula is Vdrop = Length X current X Vc / 1000.....so assumming 30 amps max demand (as pulse has worked out) 120X30X3.59/1000 = 12.924 which is just over the 5% (12V) allowed. If the Max Demand was 27 amps or less then it would come in under 12 volts. I think 4mm might be a bit light on and as you say you can spend more on the cable if you do the dirty work your self...size does matter here

.

My suggestion to you is to get your local sparky who will eventually finish & sign off on the job to work it out properly for you. Also ask about your load sharing, I'm not sure you can do it over 2 phase rural (basically 2 X 240 1 phase not 415 between them) because it can't be balanced so the neutral will take all the load anyway. I've been in industrial work too long to really know what I'm talking about with this though

Reg

**outback** · 11th January 2006, 11:15 AM

I'm pretty sure you can't balance 240v rural. MAybe Cliff isn't talking Country power which by its definition is not as flashy as city power, but ultimately more diverse and practical.

In light of this I have an extension lead, 1.5mm, plug is a bit ratty and a few bare wires if it helps Cliff.

**Cliff Rogers** · 11th January 2006, 02:47 PM

G'day.

Cairns sparky who does big jobs has said to go for 10mm² 3phase neutral & earth circular through a 40mm HD conduit.

It won't be cheap but I won't have problems running what I want & I'll have a spare core if I need more power.

It's going to be about $950 for cable & conduit & $140 for a ditch digger for the weekend. That's heaps cheaper than the original quote I got.
Mind you, I've seen the cable & it going to be like wrestling with a python to get it in the conduit & in the ground.

The Rural 2 phase is done with a centre tap pole trany on a SWER line.
It gives you 2 phases 180° out of phase so if you load up both phases, hardly any current needs to flow in the neutral at all. If one phase only is being used, the whole load goes via the neutral.
If I put the lights on one phase & the most commonly used tools IE Lathe & dust extracter, on the other, that will share the load that is on most of the time. That's what I'm on about with trying to balance the load across the phases.

Thanks all for your comments.

rrich · 11th January 2006, 03:03 PM

Cliff,
This may be of help. There is a calculator at the bottom of the page.

http://www.powerstream.com/Wire_Size.htm

Oh, in the calculator, our 240 volt single phase is what I believe someone here referenced as two phase.

**8ball** · 11th January 2006, 03:39 PM

Cliff,
I dont know how you figure it over there, but in the states, its boils down to this, 30amp underground cable is one thing, and yes you would need to consider voltage drop @ 120 meters , then next up amperage cable readilly availably is 60 amp underground cable or ( #6/3 uf ) as we call it and voltage drop wouldnt be an issue as money for any thing inbetween those two sizes would be nonstandard in the states and cost a fortune. We go from 30 amp cable to 50 amp indoors and from 30 to 60 underground, is it not the same over there?

8

**8ball** · 11th January 2006, 03:47 PM

Cliff,
I was by no meaning trying to tell you not to figure for the drop in voltage , just giving you a rule of thumb, If you wish to calculate it , I found many online sites that will do it for you if you know the specifics of the wire you plan to use, a guide to figuring it can be found at http://www.tycothermal.com/assets/No...-DROP-0901.pdf

**Barry_White** · 11th January 2006, 04:36 PM

Originally Posted by Cliff Rogers

G'day.

It's going to be about $950 for cable & conduit & $140 for a ditch digger for the weekend. That's heaps cheaper than the original quote I got.
Mind you, I've seen the cable & it going to be like wrestling with a python to get it in the conduit & in the ground.

Thanks all for your comments.

Cliff as far as putting the the cable in the conduit, just lay the cable out full length of your ditch but not in the ditch then start at each end and run each length of conduit on the cable to the centre and glue it as you go. Pulling a single length of conduit at a time over the cable is easy. When finished just tip the conduit into the ditch and cover it.

Why not use single insulated building wire instead of round cable. Building wire should be heaps cheaper than round cable and you can run your extra conductor at the same time to use later if need be.

**Cliff Rogers** · 11th January 2006, 10:35 PM

Originally Posted by Barry_White

Cliff as far as putting the the cable in the conduit, just lay the cable out full length of your ditch but not in the ditch then start at each end and run each length of conduit on the cable to the centre and glue it as you go. Pulling a single length of conduit at a time over the cable is easy. When finished just tip the conduit into the ditch and cover it.

Why not use single insulated building wire instead of round cable. Building wire should be heaps cheaper than round cable and you can run your extra conductor at the same time to use later if need be.

I had the conduit trick covered, ta.

Does single insulated building wire come in 10mm²?

**journeyman Mick** · 11th January 2006, 11:43 PM

You can get building wire in 10mm, but the sparkies I spoke to when I was running the cabling for my shed all advised against it. Apparently not so good around here as there's been cases of ants eating the insulation and wires shorting. Maybe just a very localized thing though.

Mick

**Cliff Rogers** · 12th January 2006, 12:06 AM

There were a stack of houses build out at Clifton Beach in the '90s when underground power became trendo up here that went the same way.
The bloody ants ate all the insulation on the stuff in the ground.

I know that the orange stuff on the circular is much stronger than the white poop on building wire.

Mine might cost more but it'll be there when 3 phase comes up our road.

**Dean** · 12th January 2006, 02:14 AM

And dont forget...

Dial 1100 before you dig!

**Cliff Rogers** · 12th January 2006, 11:28 AM

I did the 'dial before you dig' bit a while back.

Telstra send you a map of approx where they think it is, (very rough) & a list of registered cable finders in the area & tell you to hire the cable finder.

The only thing out the back near where I'm going to dig is my water line from the dam & I know where it is. (famous last words... I've mowed it before today.

)

**outback** · 12th January 2006, 11:43 AM

We went through this a couple of years ago. The dial before you dig sent a map. It was the wrong one, scaled to such proportions it would easily show the line from Melbourne to Brisbane. Really helpful.

**Dean** · 12th January 2006, 11:46 AM

Originally Posted by outback

We went through this a couple of years ago. The dial before you dig sent a map. It was the wrong one, scaled to such proportions it would easily show the line from Melbourne to Brisbane. Really helpful.

That's a bit crapola!
And at what cost did they flog this less than useful service off at?

**8ball** · 12th January 2006, 03:14 PM

On the subject of burried lines, in the states we had so much trouble with that, that they took the maps away from the utility companies and hired it out to a company call OUPS in my state, Ohio Utility Protection Services, they come out paint lines on the ground for you where not to dig with a bit OUPS on top , then send the bill to the correct utility company they just saved from you cutting the cables or lines. That anonym to me is a bit comical. OUPS ......

8

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