New garage light fitting tripping

[Monkey789]

Hi all, help needed!

We had an old fluorescent light in the garage and wanted to replace it with a modern LED strip light. I bought one of these from Screwfix:

https://www.screwfix.com/p/lap-single-5ft-led-batten-white-30w-2700lm/1079v

I’ve removed our old light and was expecting the power cable twin and earth and the switch cable - but found a third twin and earth connected to the light that just goes into the wall towards the house.

On the new light fitting there isn’t an earth terminal, just live and neutral.

I’ve connected all the wires into the right live/neutral terminals on the light fitting and left the earth. It’s a plastic light so I assume the earth isn’t needed?

When I turned the power back on, the light comes on straight away and if you press the light switch, the power trips on the RCD.

No matter what I do, as soon as I add the switch cable it trips.

I’ve left the switch out so at the moment it’s “always on” which isn’t ideal.

I’ve done some searching and could it be something to do with the neutrals? Do they need to be connected in a terminal block rather than via the light fitting?

So the cables I have are:
White twin and earth that I assume is the power
White twin and earth for the switch
A grey twin and earth that goes into the wall and not sure what it is connected to.

Any help would be appreciated.

Thanks.

 

[bernardgreen]

The "unknown" third twin&earth may be supply to another lamp(s)

The Black ( or Blue ) from the Switch cable is NOT a Neutral, it is a Switched Live. If it is connected ( incorrectly ) to the real Neutral the switch short circuits Live to Neutral and hence the MCB trips.

The high current in the short circuit may have damaged the switch and it may fail in the near future.

 

[terryplumb]

Are you certain it trips an RCD ,not an MCB ?
Sounds like you may have connected line to neutral at the switch cable ,that would trip an MCB.
Can you post pics of the connections at the light fitting ?

 

[Monkey789]

The "unknown" third twin&earth may be supply to another lamp(s)

The Black ( or Blue ) from the Switch cable is NOT a Neutral, it is a Switched Live. If it is connected ( incorrectly ) to the real Neutral the switch short circuits Live to Neutral and hence the MCB trips.

The high current in the short circuit may have damaged the switch and it may fail in the near future.

View attachment 175046

There’s literally no other lamps nearby and the cable goes downwards so it’s like it’s not connected to another light.

So where would the switched live need to be connected? Would it be with the other lives?

Appreciate the responses.

 

[Monkey789]

Are you certain it trips an RCD ,not an MCB ?
Sounds like you may have connected line to neutral at the switch cable ,that would trip an MCB.
Can you post pics of the connections at the light fitting ?

I’ll try and get a pic tomorrow in natural light.

On the new light fitting there’s literally just live and neutral, nothing else. There’s also almost no room to put a terminal block in there if that’s what I need to do.

 

[EFLImpudence]

So where would the switched live need to be connected? Would it be with the other lives?

The switch is placed between the supply live and the light so that it can switch the power on and off.

There will only be one actual Line(Live) wire. What any other red wires do we don't seem to know yet.

 

[Monkey789]

The switch is placed between the supply live and the light so that it can switch the power on and off.

so by that, it can go in the live terminal block on the light fitting with the power live?

and the random extra cable that I don’t know what it does can go in there too?

 

[Monkey789]

The random extra cable seems to go into the switch in the conservatory to control a combined light/ceiling fan.

 

[terryplumb]

so by that, it can go in the live terminal block on the light fitting with the power live?

and the random extra cable that I don’t know what it does can go in there too?

Only the live that comes from the switch goes into the live terminal on the light fitting . Neutrals go into the neutral terminal.
Your light is staying on permanently because you have connected the permanent live to the fittings live terminal.
Please answer my question is it an MCB that trips not an RCD.

 

[Monkey789]

Only the live that comes from the switch goes into the live terminal on the light fitting . Neutrals go into the neutral terminal.
Your light is staying on permanently because you have connected the permanent live to the fittings live terminal.
Please answer my question is it an MCB that trips not an RCD.

I’ve Googled what an MCB is and yes, it’s one of those.

I’ve put the neutrals into the neutral terminal and that’s why the switch is tripping. So where do the live and neutral go from the switch?

 

[EFLImpudence]

Neutral is not a name for any old Black or Blue wire.
Neutral is the wire which completes the circuit from the light back to the supply.

You are obviously connecting the switched live coming back from the switch to the actual neutral wire.

 

[terryplumb]

The switch would not have a neutral connected to it. Are your cables conductors coloured red and black ?
If so the black one from the switch ,is the switched live ,and it goes into the light fittings live terminal . that is THE ONLY conductor that you put into that terminal, and the only other one in there is the internal cable of the light fitting.
The red conductor of the same cable does not go to the light fitting ,but is fitted into a totally separate terminal block with the permanent live ( you may have to buy that terminal block)

 

[EFLImpudence]

https://www.diynot.com/wiki/Electrics:Lighting-Circuit-layouts

 

[Monkey789]

Right, I thought I was following your instructions but I’m clearly not getting something right. The MCB was popping and not allowing me to put on.

I’ve attached a picture.

The connected cables are the main supply.

The cable from the left is coming from the switch.

And the grey cable at the back is what I’ve discovered to be powering the conservatory light/fan. (I’ll connect this up once I’ve solved the light issue). This garage light was clearly used to for the conservatory light power when it was built.

 

[terryplumb]

Firstly all the loose conductors need to be insulated ,preferably in six individual connector blocks. If you don't have any then temporarily use insulation tape. Then see if light comes on without tripping breaker.
Secondly ,we can't see if the cables are as you say they are. But if you are correct ,the light should come on ,and stay on ,if you insulate all the other conductors. We can then tell you how to connect the rest.
Do you have a multimeter ??