Why isn't 3-core cable the standard for lighting circuits?

[veedee]

With 3-core and earth

- The lighting circuit is future proofed (e.g. many smart switches require neutral at the switch)

- You have neutral, COM and Switched live at both the light fitting and switch. So if the user wishes to extend the the lighting circuit in the future, they have the option of taking power from any switch or light fitting.

Given the benefits, why isn't the use of 3-core and earth the norm in modern electrical work?

Sparks will probably say 'cost'.

But there's hardly any difference in the price between 2-core and 3.

And when you think of the cost one would spend to call a spark out to 'provide neutral at the switch', plus remedial work if making good is required this seems like a no brainer.

Or is there something I am missing?

 

[JohnD]

Inertia.

 

[Murdochcat]

The intelligent ones already loop at the switches so the neutral is there.

The regs have suggested that including the neutral at the switches should be "considered" or another wishy washy term for a while

I always use 3C + earth for new outside lights

 

[ericmark]

It was when mothers house was rewired. Technically wrong as extra core should be grounded if not used, but it was left there for use as two way or neutral in the future.

 

[veedee]

It was when mothers house was rewired. Technically wrong as extra core should be grounded if not used, but it was left there for use as two way or neutral in the future.

To create a new light fitting, I took power from an existing ceiling rose using 3 core and Earth.

So I have a spare core, which i placed in a Wago 221 connector

Based on what you've said, I shouldn't have done this as the extra core needs to be grounded?

So to abide by best practice/safety, am I right in saying the cable needs to be replaced with 1mm 2 core and earth?

 

[davelx]

Just connect the spare core to the earth terminal at each end (as well as the (hopefully G/Y sleeved) earth core). Then it's there if you need it in the future.

 

[ericmark]

Technically one end of any unused core should be earthed, but I would not worry about it.

 

[DetlefSchmitz]

Technically one end of any unused core should be earthed, but I would not worry about it.

I'd be interested to learn which regulation number says this.

 

[Risteard]

I'd be interested to learn which regulation number says this.

In his defence I would suggest that it's accepted good practice to Earth unused cores, however it's certainly not a requirement in BS7671 terms.

 

[ericmark]

I don't think there is a regulation, but good practice, any cores not earthed can pick up voltage due to capacitive and inductive linking, but it would depend on cable lenght.

 

[EFLImpudence]

Sparks will probably say 'cost'.

But there's hardly any difference in the price between 2-core and 3.

At Toolstation, 100m of 1mm², the 3-core+E is 41.75% dearer than T&E.

We didn't know the future.

 

[JohnW2]

Technically one end of any unused core should be earthed, but I would not worry about it.

It's one thing one can do with an unused core, However, I'm not sure where that "should" comes from - do you believe it is some sort of regulatory requirement?

As far as I am concerned, simply 'safely terminating' (in a wago, connector block or whatever), or 'doubling it up with a core that is used, are equally acceptable practices - certainly as far as 'safety' is concerned.

 

[sparkwright]

Personally, I put unused cores into a connector block or wago at each end.
I prefer not to connect them to the earth terminal.
Reason being, I don't feel it's technically correct to connect unused wires to used wires.

We see it on this forum - a core connected to the earths - all of a sudden, alarm bells start ringing, and people demand to know what the hell is going on.

Then there's always the fear that someone will come along, see an used core connected to the earth terminal, and then question whether that core is actually providing an earth for something, somewhere.

To me, connected unused cores to earth just complicates things for the next man.

 

[SUNRAY]

Personally, I put unused cores into a connector block or wago at each end.
I prefer not to connect them to the earth terminal.
Reason being, I don't feel it's technically correct to connect unused wires to used wires.

We see it on this forum - a core connected to the earths - all of a sudden, alarm bells start ringing, and people demand to know what the hell is going on.

Then there's always the fear that someone will come along, see an used core connected to the earth terminal, and then question whether that core is actually providing an earth for something, somewhere.

To me, connected unused cores to earth just complicates things for the next man.

How does it complicate anything?

 

[JohnW2]

How does it complicate anything?

I presume he means that, as he wrote, if someone subsequently finds a conductor (particularly an insulated one) which is not identified by G/Y insulation or sleeving connected to an earth terminal, they might wonder (and perhaps 'have to investigate') whether it is performing some 'earthing function' for something.