what electric cable

[spitfire]

Hi just need a bit of advice been having problems with electric ,we have got three wires coming from house where the meter for the farm is they need replacing ,We have a 15kva transformer ,the wires to the buildings stretch for about 60m ,would I be able to use one cable and what would I need any help welcome.

 

[simon-0116]

Hi just need a bit of advice been having problems with electric ,we have got three wires coming from house where the meter for the farm is they need replacing ,We have a 15kva transformer ,the wires to the buildings stretch for about 60m ,would I be able to use one cable and what would I need any help welcome.

So are the cables yours. Any thing after meter is yours.
Is it 3 separate cables, or 3 twisted together.
Presume single phase ?

 

[spitfire]

So are the cables yours. Any thing after meter is yours.
Is it 3 separate cables, or 3 twisted together.
Presume single phase ?

Its our cable three separate wires single phase

 

[upnortheast]

Get your electrition to calculate what is needed based on distance X load

 

[Gerbert]

And get a few sizes bigger then what you think you might need some day.

 

[Exfarmer]

If it is single phase, you only need two core, supply and neutral, then an earth stake at the building.
if you are burying it then I would definitely oversize.
however a simple calculation based on your current transformer would suggest you could get away with a 16mm armoured . The armoured does have an earth in it but it does not meet todays regs.

 

[spitfire]

If it is single phase, you only need two core, supply and neutral, then an earth stake at the building.
if you are burying it then I would definitely oversize.
however a simple calculation based on your current transformer would suggest you could get away with a 16mm armoured . The armoured does have an earth in it but it does not meet todays regs.

Thanks for the reply measured today its 90m don't want to go underground as it would involve digging up the whole lawn drive and concrete yard ,would I be able to put armoured cable on existing poles .

 

[TechWise]

Consult a qualified electrician to advise on the size of cable and what type you need to use. They will also tell you the proper earthing arrangements as I believe an earthing rod is unacceptable in most situations - although it's a few years since I was last trained up on the regs.

 

[Mur Huwcun]

Consult a qualified electrician to advise on the size of cable and what type you need to use. They will also tell you the proper earthing arrangements as I believe an earthing rod is unacceptable in most situations - although it's a few years since I was last trained up on the regs.

From some work that was done here by one electrician and another firm doing upgrade and extension work at my workplace armoured cable earth is not heavy enough on three phases and needs another earth cable put in. Same with twin and earth cable, the earth is not heavy enough if it’s a supply cable! It’s all quite interesting when you get chatting to the electricians

 

[TechWise]

From some work that was done here by one electrician and another firm doing upgrade and extension work at my workplace armoured cable earth is not heavy enough on three phases and needs another earth cable put in. Same with twin and earth cable, the earth is not heavy enough if it’s a supply cable! It’s all quite interesting when you get chatting to the electricians

I think the concern is that if the armour is damaged or corrodes away before the inner conductors then you can lose your earth without knowing. Also, I think the armour is usually made of steel which is not as goog a conductor as the live wires which will be copper so could lead to a high earth resistance. You're also not allowed to use your water pipes as an earth as someone could do a repair and replace a section of pipe with plastic then that's your earth gone.

I'm an electrical engineer and not an electrician so I am not trained up on the specific regulations for specific settings. I do know that our sparky said it's difficult to get sparks who can work on farms as the regs are tight and the majority of people coming out of college can just about wire a knew build from scratch but aren't up to the stricter farm and industrial stuff or diagnosing and modifying existing wiring. He reckoned a lot of them didn't even understand 3-phase because they were quite happy changing light bulbs for little old ladies!

 

[milkloss]

If you can get a genuine earth piped straight in then do it. It will save a lot of hassle. Earth rods are fine and all many farms will have one.... us included. You'll need a spark to test the earth to make sure it's good enough. Get him to put in a decent isolator and main RCD, the rest you can mess about with at your leisure (provided you get it tested before use of course!)

 

[Exfarmer]

Thanks for the reply measured today its 90m don't want to go underground as it would involve digging up the whole lawn drive and concrete yard ,would I be able to put armoured cable on existing poles .

you will need 25mm cable for that run
Problem with armoured overhead is that it is such a weight and i am certain you will need several poles for that length.
I did not think that there is a requirement to use armoured over head, others may put me right
is there any chance of moling it in ?

 

[upnortheast]

Only have one OH armoured (Try to avoid if at all poss ) The sparky tensioned a steel cable across (it`s only about 15m) & clipped the armoured to that
There is a proper name for that but forgotten it.

 

[bobk]

you will need 25mm cable for that run
Problem with armoured overhead is that it is such a weight and i am certain you will need several poles for that length.
I did not think that there is a requirement to use armoured over head, others may put me right
is there any chance of moling it in ?

Bet it's 35mm swa , that's what we had to put in .
Best underground and you say it's heavy

 

[Exfarmer]

Of course the one thing the OP has not mentioned, is the use he has for it
if it is just couple of Led security lights or for calving etc, then 25mm will be grossly in excess of requirements.
if however he wants to run a 10 hp motor ( best not off 15kva. Feed ) then he will need the full 25mm.
of course there is the issue of future proofing.
I would not under any circumstances recommend just using twin and earth 2.5 grey cable but it would certainly run plenty of lighting, and from screwfix would not cost a lot

 

[steveR]

I'm an electrical engineer and not an electrician so I am not trained up on the specific regulations for specific settings. I do know that our sparky said it's difficult to get sparks who can work on farms as the regs are tight and the majority of people coming out of college can just about wire a knew build from scratch but aren't up to the stricter farm and industrial stuff or diagnosing and modifying existing wiring. He reckoned a lot of them didn't even understand 3-phase because they were quite happy changing light bulbs for little old ladies!

Never a truer word... I had a local company, since gone bust I think, rewiring the farm buildings two years ago. One of the guys knew his stuff, the rest were pleasant, but pathetic and struggled with a non domestic environment. Senior bloke had to keep an eye on the two doing the work, as did I.

Ran a new SWA cable from the meter to the buildings, all ovehead until I bury some of it, as they were having issues with existing lighting causing trips to go! That wasn't the problem and although the old cable was due for replacement, it wasn't actually needed. Happily, I never paid their "final" bill, as I told them that the finance girl had not completed the contracted works yet. Still need to get a sparky back one day....

 

[upnortheast]

Only have one OH armoured (Try to avoid if at all poss ) The sparky tensioned a steel cable across (it`s only about 15m) & clipped the armoured to that
There is a proper name for that but forgotten it.

Support is called catenary wire
Also noticed this
IEE Selection & erection Guidence Notes, Tables I.

Table I3 : Max horizontal unsupported span 3m, minimum height if vehicles pass under it 5.8m, or 3.5m high if vehicles do not pass under.

 

[Exfarmer]

Support is called catenary wire
Also noticed this
IEE Selection & erection Guidence Notes, Tables I.

Table I3 : Max horizontal unsupported span 3m, minimum height if vehicles pass under it 5.8m, or 3.5m high if vehicles do not pass under.

A question for you @upnortheast can you still use single core cable for overhead? Very long time since I helped install some.

 

[upnortheast]

Sorry, don`t know the answer to that

 

[defender]

There is no need to use armoured cable unless you are burying the ends in the ground or where it is likely to get damaged , for over head only all you are doing is adding weight.
25 mm cable ok for 60 metres at 15 kava . I would suggest split concentric as a bit cheaper and the live is protected . Catenery wire or even a high tensile wire and clip on to that