Consumer Unit Replacement

[securespark]

I had the same thought. Counting and measuring the strands in the conductor would tell you.

 

[JohnW2]

I had the same thought. Counting and measuring the strands in the conductor would tell you.

I don't think that counting would help, since 7/0.029", 7/0.036" and 7/0.85mm (4mm²) all have 7 strands - but measuring the strands would obviously do it.

Kind Regards, John

 

[securespark]

Well, if the cable was 3/0.036, it would be obvious.

 

[JohnW2]

Well, if the cable was 3/0.036, it would be obvious.

Very true - but, given the external dimension the OP has told us, it would seem unlikely that it's 3/0.036, wouldn't it?

Kind Regards, John

 

[securespark]

As it is imperial and insulation was often thicker, I don't know what the measurements would be.

 

[JohnW2]

As it is imperial and insulation was often thicker, I don't know what the measurements would be.

Indeed. I don't know whether we are actually sure that it is Imperial. If it were, like you, I don't know what the dimensions would be, but 4.2mm OD would seem very large for a single-insulated ~1.5mm² conductor. Anyway, this is all speculation - if the OP is able to measure (and count) the strands, we will get an answer.

Kind Regards, John

 

[Risteard]

However...
And that does say they have to go through the same hole. I wasn't sure if the regs said that, or if (as they could well have done) they only required conductors to be arranged to avoid problems of electromagnetic heating.

So there's another thing your bungling soi-disant electrician bungled.

Fortunately, as we know, the currents in your cables will never be high enough to cause any significant heating.

Every Electrician knows that it is mandatory for live conductors to enter ferromagnetic enclosures together (unfortunately fewer understand that the cpc or Earthing conductor also MUST. How on earth (excuse the pun) were you not aware of this? Are you competent to be carrying out electrical work? Do you want a reading list?

 

[ban-all-sheds]

I've never needed to know, or needed to advise anybody.

I do know that at the currents encountered in domestic installations electromagnetic heating effects are not a problem, and I do know that it was quite possible for the regulations to have had a requirement along the lines of "care shall be taken to avoid damage from heating effects where conductors enter ferromagnetic enclosures" as that is just the sort of thing they say elsewhere.

I am competent, and I need no instruction from you.

 

[JohnW2]

Every Electrician knows that it is mandatory for live conductors to enter ferromagnetic enclosures together (unfortunately fewer understand that the cpc or Earthing conductor also MUST.

That latter bit ("MUST") may be theoretically true, but if the installation were such that a sufficiently high current could flow in a CPC or Earthing conductor for a sufficiently long time that there would be significant heating effects if it did not pass through the same hole as the live conductors, I think one would probably have a lot more to worry about than which conductors were passing through which hole.

Kind Regards, John

 

[OwainDIYer]

That latter bit ("MUST") may be theoretically true, but if the installation were such that a sufficiently high current could flow in a CPC or Earthing conductor for a sufficiently long time that there would be significant heating effects if it did not pass through the same hole as the live conductors, I think one would probably have a lot more to worry about than which conductors were passing through which hole.

And what happens when you have multiple circuits but only one cpc.

 

[JohnW2]

And what happens when you have multiple circuits but only one cpc.

I'm not quite sure how that would/could arise. Any final circuit will (should!) have its own CPC - either within a T+E cable(s) or as a separate conductor if wiring is in singles. What situation did you have in mind?

Of course, the theory would break down in the (very rare) case of a fault arising between a live conductor of one circuit and the CPC of another circuit - but that is so rare (and pretty irrelevant in a domestic installation) that it's not worth worrying about (and the only way of addressing it would be to put all live conductors {of all circuits} and all CPCs {of all circuits} through just one hole!)

In the case of the meter tails, the (one) earth conductor plus any/all main bonding conductors should theoretically all go through the same 'hole' - but, again, of no real importance in a domestic installation.

Kind Regards, John

 

[ban-all-sheds]

I doubt that main bonding conductors are classed as cpcs.

The main earth, yes, but not bonds.

 

[JohnW2]

I wouldn't class main bonding conductors as CPCs either. However, if they didn't go through the same hole as the Earthing Conductor (hence also the L&N tails), if, in the very rare situations we hear so much about, a very high current flowed from earthing conductor to a bonding conductor, those who worry about such things would have eddy current heating to worry about.

 

[OwainDIYer]

I'm not quite sure how that would/could arise. Any final circuit will (should!) have its own CPC - either within a T+E cable(s) or as a separate conductor if wiring is in singles. What situation did you have in mind?

I didn't think you needed multiple cpcs if wiring in singles, just one large enough for the largest circuit carried.

 

[JohnW2]

I didn't think you needed multiple cpcs if wiring in singles, just one large enough for the largest circuit carried.

Dunno - I've never wired in singles - so you'd have to ask someone else. However, if one did as you suggest, one presumably could not, for example, test the continuity of the CPC in a ring final circuit.

Mind you, with singles, I suppose that there are not necessarily any (cable) CPCs at all - it could all be conduit. In that case, it would not have to pass through any hole, anyway - but I am again uncertain as to if/how would could/would do certain aspects of testing.

In any event, as I've said before, although I suppose that there is a theoretical argument that the Ls, Ns and CPCs of all circuits should pass through the same hole, there should never be high enough currents in the CPC for long enough for there to be an issue if one didn't - probably in any situation, but certainly in a domestic or commercial environment.

Kind Regards, John