Extending incoming supply 75M

[msg]

Hi

I have an existing supply at the boundary of my property. I believe it to be TNS.
At the incoming junction , I supplied the white box , Rotary isolation , 80ma RCD and an Earth rod. EDF contractors supplied the meter , fuse and made the connection.
So out of the brick box containing all of this I ran a temp 3 core 16mm SWG cable to my building 75M away whilst I was building. Bonded the earth cable to an earth rod and clamped the armour to earth also.
This also has an earth rod at the house bonded to the earth
Now I need to tidy things up and bring a new heavier 25mm supply to the new building.

My question is , What arrangement can I use to extend the supply.
Do I need to treat it as T&E and therefore use 3 core SWG or can I use 2 core and re-bond Neutral to earth at the house. (will this trip the RCD at the meter end)

I am a new member and would like to thank in advance anyone taking the time to answer questions.

Mark.

 

[Rockingit]

It is not allowed under various parts of different regulations to create your own Protective Earth Neutral (PEN) conductor in the manner that you describe. If you have a TN-S supply then that is what you should use, and take the earth from the point of origin into the house (assuming that you don't want to keep the TT).

I'm guessing you'll have put in the temp earth rod in order to satisfy the requirements for it being a building site?

If it were me, I'd fit a KMF (fused double pole main switch) next to the meter then run my 25mm SWA from it to wherever you need to get to. You don't need to RCD protect the SWA on this run.

The Copper Eq. csa on a 25mm SWA is sufficient to allow you to only run a 2 core cable, so long as the armour is properly glanded to be used as the earth instead.

 

[JD6400]

Hi msg , please don't take offence but get a electrician in . From the several mistakes in terminology that your op contains it is obvious that you could do with some on site help with this one .
I am not trying to be obtuse but some times it is best / safer to get a professional in .

 

[msg]

Hi Rockingit

Thankyou for your advice.. I will do as you suggest. At least I know what cable to buy now.
Thanks again
regards

 

[msg]

Hi JD6400

No offense taken. I am just trying to keep the cost down by doing the ground work myself.
At least I learn that way etc. I will get a professional in to check etc once I have done the donkey work.
Thanks for your reply
Regards

 

[Engineer54]

I agree with JD6400, in that you really do need to bring in a ''Qualified'' electrician at this point of bringing in your permanent main power supply cable.

No you most certainly cannot make your own N-E connection, this is solely DNO's domain/territory only they will know the supply characteristics on their local network distribution system.

If you have been provided with a DNO TN-S earthing point then that's what you use!!

Don't forget that the 25mm SWA cable needs to be buried at around 600mm throughout it's buried length and be laid on a bed of sand and surrounded by sand (there is a cable trench procedure that needs to be followed). I would disagree with Rockinit in choosing to use a 2 core SWA cable over this 75m run. The chances are, that sheath damage is going to occur especially if you intend doing this yourself, far better to use 3 core SWA, at least then if the wire armouring corrodes away over time, the main earth core will still be intact.

 

[Rockingit]

I would disagree with Rockinit in choosing to use a 2 core SWA cable over this 75m run. The chances are, that sheath damage is going to occur especially if you intend doing this yourself, far better to use 3 core SWA, at least then if the wire armouring corrodes away over time, the main earth core will still be intact.

That's a fair one! In thinking about it, over that distance then yes, 3c is the way forward.

 

[telectrix]

i'd run 3 core SWA in a duct, 600mm deep with warning tape at 300mm.(ish). surround ducting with sand and put a draw rope in as well, just in case. let your electrician see it before it's filled in. he can then test it to ensure it's sound.

 

[msg]

I agree with JD6400, in that you really do need to bring in a ''Qualified'' electrician at this point of bringing in your permanent main power supply cable.

No you most certainly cannot make your own N-E connection, this is solely DNO's domain/territory only they will know the supply characteristics on their local network distribution system.

If you have been provided with a DNO TN-S earthing point then that's what you use!!

Don't forget that the 25mm SWA cable needs to be buried at around 600mm throughout it's buried length and be laid on a bed of sand and surrounded by sand (there is a cable trench procedure that needs to be followed). I would disagree with Rockinit in choosing to use a 2 core SWA cable over this 75m run. The chances are, that sheath damage is going to occur especially if you intend doing this yourself, far better to use 3 core SWA, at least then if the wire armouring corrodes away over time, the main earth core will still be intact.

Hi All

I have already run a 62mm duct to take the cable at a depth suitable. I have also run warning tape , 200mm above the ducting. I will consider myself told! I will run 3 core as you suggest as a double precaution that way if the ducting and the armour gets damaged I am covered.

Thanks for all your help and yes I will get a ''Qualified'' electrician at this stage.

Regards

 

[msg]

Hi All

Just found the reply to thread button!! New to this.

Reading a bit more about this subject, It would appear that I could have a TT arrangement as I supplied the earth! .

The consensus from the forum so far is that I use 3 core SWA and extend the existing arrangement .

I will however employ an electrician (qualified) at this point as suggested!

Thanks for all replies

 

[JD6400]

The op has not mentioned whether the 75m run is under his garden or if it will be passing through a field that is in agricultural use . If it is the latter of the two , it is worth noting that the depth will need to be 1000mm and not the usual 600mm .

 

[telectrix]

good point.

 

[Octopus]

Hi

I have an existing supply at the boundary of my property. I believe it to be TNS.
At the incoming junction , I supplied the white box , Rotary isolation , 80ma RCD and an Earth rod. EDF contractors supplied the meter , fuse and made the connection.
So out of the brick box containing all of this I ran a temp 3 core 16mm SWG cable to my building 75M away whilst I was building. Bonded the earth cable to an earth rod and clamped the armour to earth also.
This also has an earth rod at the house bonded to the earth
Now I need to tidy things up and bring a new heavier 25mm supply to the new building.

My question is , What arrangement can I use to extend the supply.
Do I need to treat it as T&E and therefore use 3 core SWG or can I use 2 core and re-bond Neutral to earth at the house. (will this trip the RCD at the meter end)

I am a new member and would like to thank in advance anyone taking the time to answer questions.

Mark.

I'm astonished that EDF would do this without some form of certificate provided by a competent person!