Wiring for lights

[crispy_wafer]

As my nice spark is busy on other commitments he's given me permission to run up cables for switches and lights.  I've done most of the easy 'loop at' switches now and now my attention is turning to running cable up to the pendant or downlight.  I asked him what cable I should use he say t+e is fine.  but I read this where @TonyT mentions running 3 core + e to lights?  What's a good reason for this?  What would I be loosing by just using t+e?  ta.

 

[ProDave]

The only reason you might want 3 core is if you plan to have a light fitting that needs a permanent live, perhaps it has a sensor for automatic operation?  or perhaps you want a light and fan?

 

If you are certain it will just be a light controlled from the switch on the wall then no need.

[Andehh]

Wish I'd run 3 core, just for future proofing. Small investment for a 'just in case' over next 10 years.

[FuerteStu]

16 minutes ago, ProDave said:

The only reason you might want 3 core is if you plan to have a light fitting that needs a permanent live, perhaps it has a sensor for automatic operation?  or perhaps you want a light and fan?

 

If you are certain it will just be a light controlled from the switch on the wall then no need.

Second reason is for multiple switching of banks of lights. 

 

You can have two rows of spots switched separately from one cable. 

 

Helps reduce the number of wires if youre looping in the switch! 

 

Just gives you options for an almost identical amount of work and cost

[crispy_wafer]

8 minutes ago, FuerteStu said:

Second reason is for multiple switching of banks of lights. 

 

You can have two rows of spots switched separately from one cable. 

 

Helps reduce the number of wires if youre looping in the switch! 

 

Just gives you options for an almost identical amount of work and cost

 

This is possible with our plan, especially in some rooms where we have a mix of brighter lighting and softwer lighting, so what you are saying is, it would be either a double switch with 2 * t+e cables or a double switch with a single 3 core+e cable out to the fittings?

[Temp]

Historically a single 2+E has been run down to switches. The blue (Neutral) wire in this is sleeved brown and used to provide switched live back up to the light fitting. This means there is no Neutral wire at the switch.

 

Most dimmers don't need a Neutral but I think some home automation devices may require one. I'd use 3+E.

 

An extra wire is also needed where you have two way switching (two switches controlling the same lights). These switches need Live, two Switched Lives and possibly a Neutral. Total 4+E, normally done as Two 2+E ?

[FuerteStu]

6 hours ago, crispy_wafer said:

 

This is possible with our plan, especially in some rooms where we have a mix of brighter lighting and softwer lighting, so what you are saying is, it would be either a double switch with 2 * t+e cables or a double switch with a single 3 core+e cable out to the fittings?

It allows for 2 different switched lives and a neutral (plus earth) in the same cable this can then be bounced to the start of each string of switched fittings, or along all of them and just picking your fittings depending on choice. 

 

My living room has two central fittings on a dimmer and perimeter spots along the back and window walls. 

 

This gives 3 different moods from the same cable

[FuerteStu]

Or, as @ProDave mentioned.. The permanent live for a smart fitting.

 

Or like my fittings in the hallway and above my consumer unit, an emergency fitting that charges the battery up and when the permanent live drops out, allows an exit route, or lighting over the fuse board to flick the breaker back on