External lighting too many wires

[Shakey Baby]

Hi,

Bought a new external light fitting to replace an old existing one. The problem is the colour of the wires and fitment to the old unit doesn't make any sense in relation to the new fitting. From the house feed there are two sets of cable coming out. The red wires were twisted together, the two earths twisted together also, and two black wires connected into the old choc block into two seperate terminals. The appears to be a switch for the light fitting inside the back door. With out the use of a volt meter is there anyway to work out which wires need to go into the new fitting which has the following connections Blue/Brown/Earth/L1
Hope you can help

Shakey

 

[JohnD]

At a guess:

Your lamp is at the end of the lighting circuit, so it does not have a loop-in and a loop-out.

So one of the twin-and-earth cables is the supply, and one is the switch.

So the incoming phase (red) will be always live, and it has been connected to the red that goes to the switch.

At the switch, the incoming live red wire is switched onto the black of the same cable. (so it ought to be sheathed red in the switch enclosure) and when it returns to the light fitting, this black will be live phase when switched on (so should be sheathed red again)

This red-sheathed black is the switched live, which should go to the brown of the lamp. The other black is the neutral (unswitched) which goes to the blue of the lamp.

You will need a connector block, which may be provided in the lamp fitting, if not you can buy one and enclose it out of any possible water or touch, preferably inside the light fitting. Into this put the twisted reds and earths. If the lamp fitting is of metal it will have an earth connection to be made to the twisted g/ys.

 

[pcboffinuk]

Hi Shakey,

I'll have a go, although I'm sure someone more expert will be along later to offer further advice.

Sorry if this is teaching you to suck eggs, but firstly be very careful about working on the wiring and DON'T assume that it isn't live just because the inside switch is off. If you don't have a multimeter (these days you can get them for less than £10 so worthwhile having one around) then turn off at the Consumer Unit (fusebox). If you aren't sure what circuit the light is on then better to turn the whole house off than find out the hard way.....

The colour difference is the easy part - until recently fixed wiring was RED for Live and BLACK for Neutral - Green/Yellow was and still is earth. The new colours (to match plug wiring) are BROWN for Live and BLUE for neutral.

From what you say I think you have the following:

One of the cables is from the main supply (and will be live even with the switch off hence my warning) - The Live (RED) from this this is connected to the switch wire, which goes to the switch, and returns via the black wire (which in this case is being used as a switched live - if so it should have red sleeving at the end of it to denote this but that may not have been done).

The other black is the return Neutral to the main supply.

that would suggest that the switched live should go to the Brown connection on the light, the neutral return should connect to the blue, and the Earth to the Earth.

The tricky bit may be working out which is the switched live - for that you would really need a multimeter, unless you can work out visually which cable goes to the switch.

You also mention a L1 connection on the new light though - it sounds as if you have a light which requires a permanent feed and a switched feed - does it perhaps come on at low level automatically at dusk, then full level when switched on? Does it have a PIR movement detector fitted? If the instructions say that a permanent live feed is also required this could come from the twisted red cable, but the instructions should be clear on this.

Finally, the wires that you say are twisted together should really be secured with choc block or crimps - ensure at least that they have a good connection as this may cause trouble later on.

I hope that helps, but if you are in any doubt then ask again - I'm sure someone will be able to put you right and it is much better to appear foolish by asking a silly question than to appear foolish with spiky hair and a burning smell

Regards

Gavin

 

[pcboffinuk]

Damn, will have to learn to type faster Good to know that I agree with John though

One thing I seem to recall is that an outside light should be on an RCD? Don't have the books at hand at the moment but I'm sure someone knows?

Gavin

 

[JohnD]

Damn, will have to learn to type faster Good to know that I agree with John though

One thing I seem to recall is that an outside light should be on an RCD? Don't have the books at hand at the moment but I'm sure someone knows?

Gavin

Tee hee!

Lighting doesn't have to be on an RCD.

I missed the bit about L1 even if it isn't for permanent live, it might be to park the twisted reds - the instructions should say. And there is a terminal for the twisted earths, so it sounds like no need for a separate block.

 

[scousespark]

The L1 may be there in case you are going to run more than one light from the one switch, and is used to feed the next light in the series.
You should check the fitting instructions.

 

[JohnD]

RTFM, as the saying goes.

 

[Pensdown]

...or a PIR overide terminal?


Edit
or RTFR's in my case

 

[Shakey Baby]

Thanks for the help folks, just to add to the info, yes the unit does have a PIR sensor. Yes i did turn the whole house off at the mains before touching anything ( once bitten twice shy when it comes to wigglies )
Here's what i understand so far from what you have said ( not playing with it untill i'm sure of what i'm doing) One of the black wires is nutral one is switched live, and the twisted reds are perm live, the only thing i'm unsure of is what to do with the twisted reds? Do they go into the L1 ? You have 30 minutes to discuss amongst yourselves while i pop to B+Q for a volt meter. Any excuse to buy more stuff for the tool box

Rgds

Shakey

PS As for RTFM (read the F'ing manual? ) It's from B+Q so you can figure how much help it is Will learn Heprew i think it might a bit clearer then ( or any other langauge that is forgien to me, being PC sucks )

 

[Pensdown]

Your 2 reds go into Brown and your switched live goes into L1.

This will allow the light to come on at night via the PIR when it's switched off inside

Any other offfers?