Radial-Ring or Spur Electrical Wiring

[ploughman]

After reading information concerning the above I find the subject rather confusing.
My background is basically computers, so I find it a bit confusing that bot Ring and Radial seem to be the same, apparently the only difference is the protection of the circuits.

My understanding, from my experience is effective Radial and Ring similar.

Taking the the electrical circuit in my house, it has a consumer unit, this supplies various circuits, lighting and power.

The power circuit goes from the consumer unit to each power socket then on to the next, covering upstairs and downstairs, returning to the consumer unit.

The light circuit consists of 2 circuits, one for upstairs lights and the other for the downstairs. Both circuits return to the consumer unit.

Effectively all are Ring Circuits, but they are separate circuits from the consumer unit, the source of the electric

Effectively that radiate, in a ring fashion, from the consumer unit.

Spur circuit would be a lead from any point, either Lighting or Power or the consumer, which does not return to the source

 

[PrenticeBoyofDerry]

Most of your circuits will be radial circuits, they have no return legs and the conductors will stop at the extreme point of the circuit.
Where a ring final circuit does return. (you will find pairs of phase, neutral and CPC conductors at the board for these circuits)
//www.diynot.com/wiki/electrics:socket_circuits:a1_ring_final_circuit
//www.diynot.com/wiki/electrics:socket_circuits:a2_radial

 

[ban-all-sheds]

My background is basically computers, so I find it a bit confusing that bot Ring and Radial seem to be the same,

They aren't.

The power circuit goes from the consumer unit to each power socket then on to the next, covering upstairs and downstairs, returning to the consumer unit.

That's a ring. Not, we hope, 2 radials each with an inappropriately rated protective device.

The light circuit consists of 2 circuits, one for upstairs lights and the other for the downstairs. Both circuits return to the consumer unit.

If you've got two circuits, i.e. 2 fuses/MCBs, one for upstairs and one for downstairs and you can show end-to-end continuity between the conductors at the CU then they are rings, but this is unusual and unnecessary.

What's probably happened is that the house has been (at least partially) rewired by a numpty who thought that lighting circuits had to be rings, and you should start to question what other numptyisms he's bequeathed to you.

Spur circuit would be a lead from any point, either Lighting or Power or the consumer, which does not return to the source

There's a perennial debate on whether radials have spurs or branches.

 

[rjm2k]

What's probably happened is that the house has been (at least partially) rewired by a numpty who thought that lighting circuits had to be rings, and you should start to question what other numptyisms he's bequeathed to you.

I read about it being a common mistake that a lighting circuit should be a ring (perhaps because the terminology calls it a loop and what do loops do?)

Given that the whole point of a ring was to be cheaper by saving on copper, what is the actual harm in using a ring for lighting? Surely if the cable is adequate for a radial circuit, it's more than adequet for a ring? What would be more of a risk, using underrated cable in a radial, or overrated cable in a ring?

There's a perennial debate on whether radials have spurs or branches.

Assuming it's the physical layout, rings would have spurs and radials have branches, but it's different terms for the same arrangement isn't it?

 

[ban-all-sheds]

Given that the whole point of a ring was to be cheaper by saving on copper, what is the actual harm in using a ring for lighting?

Financial harm - it would not be cheaper because the cable would not be undersized, so the materials and installation costs would be higher for no reason.

What would be more of a risk, using underrated cable in a radial, or overrated cable in a ring?

The former, of course, but I said nothing about risk, I said it was unnecessary, and it is.

Assuming it's the physical layout, rings would have spurs and radials have branches, but it's different terms for the same arrangement isn't it?

The Wiring Regulations talk about spurs from radial circuits.

 

[EFLImpudence]

Assuming it's the physical layout, rings would have spurs and radials have branches, but it's different terms for the same arrangement isn't it?

According to the definitions a spur is a branch from a ring or a radial.

 

[ban-all-sheds]

So radials never branch off, they just consist of the radial, and then at some point begins a whole load of spurs?

That may be the definition, but as the recent discussion showed, it's felt that spur ought to refer to something subordinate.

If I have a string of sockets on a radial, and then at a socket somewhere between the first and the last I connect another one to it, have I then created 2 spurs, and removed a whole section of my radial circuit?

What if I add a new socket from the MCB - do I then have no radial circuit at all, just 2 spurs?

 

[EFLImpudence]

but as the recent discussion showed, it's felt that spur ought to refer to something subordinate.

That's what I think. Just quoting the definition in part 2.

It must have some relevance.