Three phase wiring

[Lightfeat]

I am trying to take a single phase supply for an 80amp CU from a three phase supply, and am a little confused by what I find.

The three phase lines are straightforward, but the negative tail from the service fusebox to the meter terminates in a large metal block in the fusebox, to which not only is the negative supply connected, but also the earths from the connected devices.

I presume that this work was installed by a professional, but can see nowhere that this earth actualy leads to earth, and why oh why are the earths connected to the neutral within the REB fusebox? If I were to take a single phase supply from this, surely to connect both neutral and earth to the same block is wrong, wrong, wrong - or so it seems to me.

Please help. I shaln't act in any way until this is resolved. Many thanks
Lucas

 

[Adam_151]

suppliers PME terminal?

 

[Lightfeat]

To the right of the three phase fuses, a large square connector block, into which both the negative tail, and the earth connections are fixed. I'm sure it is as it should be. I just don't understand it.

If I am to connect my single phase supply to a phase supply and a neutral, will the returning electricity from the CU negative be earthed? Are my earth and negative to link? This will permanently enliven my earth, no? That sounds bad to me.

I realise I am nowhere near as schooled as I ought to be on this subject - that's why I ask. Please help.

Lucas

 

[ebee]

I`m afraid that the question you are asking and the terminology you are using lead me to believe that you should not be attempting work on this circuit.
For safetys sake call an electrician.
Regards,
Ebee

 

[Lectrician]

Is this an old fusboard?? They never used to have an earth terminal - relying on the fact you where using galv trunk/conduit etc etc.

Possibly someone has decided that they will PME it themself

When you say they go into the same block - do they go into the same terminal, or a different area of the block? Are you sure it isn't two blocks next to each other - the earth one bonded to the case??

A photo would be good.

Is this board at the origin? It could be a ryfield or similar type board designed for use by the DNO.

 

[andy]

I am trying to take a single phase supply for an 80amp CU from a three phase supply, and am a little confused by what I find.

The three phase lines are straightforward, but the negative tail from the service fusebox to the meter terminates in a large metal block in the fusebox, to which not only is the negative supply connected, but also the earths from the connected devices.

I presume that this work was installed by a professional, but can see nowhere that this earth actualy leads to earth, and why oh why are the earths connected to the neutral within the REB fusebox? If I were to take a single phase supply from this, surely to connect both neutral and earth to the same block is wrong, wrong, wrong - or so it seems to me.

Please help. I shaln't act in any way until this is resolved. Many thanks
Lucas

earth and neutral come from the same point of a transformer. this is rpetty basic stuff, and if you dont understand this you should not be attempting any electrical work. especially where 3 phase is involved

 

[shortcircuit]

To the right of the three phase fuses, a large square connector block, into which both the negative tail, and the earth connections are fixed. I'm sure it is as it should be. I just don't understand it.

If I am to connect my single phase supply to a phase supply and a neutral, will the returning electricity from the CU negative be earthed? Are my earth and negative to link? This will permanently enliven my earth, no? That sounds bad to me.

I realise I am nowhere near as schooled as I ought to be on this subject - that's why I ask. Please help.

Lucas

For your information, you cant see it, you cant hear it, you cant smell it if you touch it it will KILL YOU VIRTUALLY INSTANTLY

Your questions suggest you have little knowledge of what you are doing. Please consult a competent person. If you get it wrong, it goes BANG and three phase goes BIG BANG

Remember under H&S W you have resonsibilities for others

 

[vgcassule]

My friend this is a job for qualified electricians! I am sure you don't have a clue what you are doing. Don't risk the safety of the other people!
If you did this job it you broke the low '' part P regulation" This system is called PME or TNC-S which the neutral and the earth are combined.

 

[Lectrician]

Pointless post, and two years too late!

But welcome to the forums anyway.

 

[RF Lighting]

And unlikely to be covered by part p

 

[kai]

Many new installations (and indeed my 1960's house) have PME/TNCS type systems, where the system earth to connected to the neutral block of the main incoming service fuse holder block, normally emerging from the right hand side of the unit.

 

[ban-all-sheds]

And your point is?