Electric.cable...single conductor?

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Electric.cable...single conductor?

Postby Cheeryble » Wed Apr 02, 2014 10:58 pm

Hi there

We have a 400metre run to a site for a modest house.
We shall use 25sqmm Al cable unless anyone here disagrees.

Most important question first:
We have been shown a single conductor Al cable.
Does this mean that earth at the site is to be connected to the fuse box neutral rail and used as neutral?

Thanks
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Re: Electric.cable...single conductor?

Postby Cheeryble » Wed Apr 02, 2014 11:38 pm

Am I just being thick here expecting two conductors in one sheathing?
Does on simply have run completely separate conductors for +ve and neutral?
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Re: Electric.cable...single conductor?

Postby Sometimewoodworker » Thu Apr 03, 2014 11:53 am

Cheeryble wrote:Hi there

We have a 400metre run to a site for a modest house.
We shall use 25sqmm Al cable unless anyone here disagrees.

Most important question first:
We have been shown a single conductor Al cable.
Does this mean that earth at the site is to be connected to the fuse box neutral rail and used as neutral?

Thanks

Standard supply is 2 cable or may be twin core cable. Earthing is usually not done, but if you do it then it is done at the house.
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Re: Electric.cable...single conductor?

Postby Cheeryble » Thu Apr 03, 2014 12:03 pm

Thanks Woodworker

Yes I've clicked on this just never run two cables anywhere before.
My only decision now 25sqmm or 35sqmm and whether to fuse at beginning of run etc.
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Re: Electric.cable...single conductor?

Postby Destruction Del » Thu May 08, 2014 11:37 am

Does this mean that earth at the site is to be connected to the fuse box neutral rail and used as neutral?

I take it that you're on Single Phase & not 3 Phase?
Where exactly is this "Earth at the site"? did you install it?

Are you running this cable to supply a workshop, dwelling or just a machine of some kind?

In my opinion I'd go with the TN-S system, it's what we use in the UK.

The SWA (Steel Wire Armour) if any, which I doubt, should be earthed at the Step-down Transformer it's coming from.
Regardless of that, I still wouldn't trust it as a clean reliable earth.

If it was me I'd install my own copper stake as close to the consumer unit as possible (Common practice in the UK) as well as the SWA Earth, if any...

Don't tie the Earth in with the Neutral block, Tie it into ... the Earth block, use it as a clean earth which in turn will/should allow your RCD/ELCB to operate correctly.

They chose Aluminium because it a whole lot cheaper of course... Like you didn't know, but the Power factor differences between copper and Ali vary considerably, but I'd like to know the cost difference and do a little comparison one day.

My only decision now 25sqmm or 35sqmm - Here's some CCC info for you: Conductor operating temp is 70deg C
Aluminium
25mm sq will carry 78 Amps and will lose 2.9mV per Amp per Metre (The Amps refer to the load you put on - not the amount of Amps available from the source)
35mm sq will carry 96 Amps and lose 2.1mV per Amp per Metre

Copper
16mm sq will carry 86 Amps and will lose 2.7mV per Amp per Metre
25mm sq will carry 115 Amps and will lose 1.8mV per Amp per Metre


Whether to fuse at beginning of run etc

Excuse my french but most F%$king DEFINITELY!!

EVERY CABLE RUN MUST BE FUSED AT THE SUPPLY NO MATTER HOW LONG OR SHORT

E.G.
If you're going with the 25mm Aluminium core, you don't want the fuse to be over 60A, That's if you want to be sure the cable won't get stressed if theres dead short somewhere...
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Re: Electric.cable...single conductor?

Postby schuimpge » Thu May 08, 2014 7:52 pm

For 3 phase you get inspection on site, approvals for ground and everything. For 2 phase it's mostly cable and main-breaker then 'sort it out yourself'.
Have a look at my first renovation thread to see the 'old' electric installation. Work of art really.
Sparky normally had some training and some common sense, but it's those idiots from home pro et all that come and install an air con, shower heater, etc who don't give a flying fsck. Get on top of the ceiling, find a power line, scrape some mantle, twist the aircon cable around it, apply some tape... Job done... Oh and we install the cheapest china breaker we have to be sure...
Even with new projects now, I would not trust the installation as it's all quick and easy money to skip some proper electric installation above the ceiling
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Re: Electric.cable...single conductor?

Postby schuimpge » Thu May 08, 2014 7:57 pm

Oh and if you think grounding was done. Forget it unless you where there all the time and know how.
Buy a power bar with a ground indicator light at homepro , cost you maybe 500 baht. Plug it into any socket and see if it lights up or not. If not, you got a problem
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Re: Electric.cable...single conductor?

Postby schuimpge » Thu May 08, 2014 8:03 pm

My second town house gets 3-phase, grounding pin (copper), is over 3 meter long. Including cable of 75 meter (10 meter run to the meter x4 and inside the house to the box), and clamps, fittings and steel pipes it cost me less than 10k baht.
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