Wiring advice for plug in lights

[jimieee]

Hello.

I want to make a light fitting with three bulbs that plugs into the mains. I've attached a circuit diagram of what I had in mind.
I put it together, plugged in the last bulb on the circuit only (i.e. the one on the far right of the diagram), but when I turned on the power it tripped the main switch on my consumer unit.

What did I do wrong?
Is there a better way to achieve the same result?

Untitled

• jimieee
• 19 Nov 2011
• 1

 

[EFLImpudence]

That's why we do tests before energising.

Please describe the 'switch' that tripped.

You say main switch - have you an RCD (with test button on it ?) as the main switch?

Can you post a picture of your consumer unit?

The diagram is alright. What are the connectors?
Can you not wire the three lights into one?

 

[jimieee]

It's the RCD switch (with test button), as you guessed.

This is running off of a mains socket, via an extension lead, to the first connector, which is a ceiling rose.

How would you recommend I test it before powering it up again?

I took a picture of the consumer unit. The switch that tripped is the one to the far right:

Untitled

• jimieee
• 20 Nov 2011
• 1

 

[EFLImpudence]

It's the RCD switch (with test button), as you guessed.

This suggests that you have a fault to earth, either from the Live or the Neutral or the bulb could be shorting or just a stray strand of wire.

This is running off of a mains socket, via an extension lead, to the first connector, which is a ceiling rose.

I assume the extension lead is alright with other appliances.

How would you recommend I test it before powering it up again?

Ideally you need an Insulation Resistance Tester.

However, if it is an obvious fault you may be able to detect it with a multimeter on Ohms setting.
Remove the plug and test between the pins.

L to N - Should be open-circuit with no bulb(s) in, or a few Ohms with bulb(s) in.
L to E - Must be open-circuit.
N to E - Must be open circuit.

Test on all the Ohms settings.

You may get the above readings and still have the fault but
if you get a reading (other than open- circuit) between L to E or N to E then there is the fault.
If you haven't made an obvious mistake then the cable may be damaged.

 

[EFLImpudence]

I also note that your lights are on a 16A breaker.

Normally lights are protected by a 6A device.
The main circuit cable may be alright with this unless it runs through thermal insulation, in the loft for example, but I doubt that the lighting fixtures are.
Pendants and other light fittings only use 6A wiring.

 

[jimieee]

Thanks for this. It sounds as though I need to get a multimeter and test. I had a look to see if there was an obvious mistake, but couldn't find anything wrong.

 

[JohnW2]

Thanks for this. It sounds as though I need to get a multimeter and test. I had a look to see if there was an obvious mistake, but couldn't find anything wrong.

It's an outside possibility, but have you checked to confirm that the RCD still trips when there are no lamps (bulbs) plugged in to your circuit?

Kind Regards, John.

 

[jimieee]

No, I didn't try anything else, as I thought it would be better to get some advice before I did.

I will have a go, but it won't be until tomorrow now...