12v MR11 Low Voltage lighting tripping RCCB

[J5]

Hi.

I recently purchased a couple of 12volt MR11 light fittings with electronic transformers (Live & Neutral input, no earth).

I have connected them but every time I switch them on it results in half the Consumer Unit going off after tripping one of the 63A RCCBs. The individual 6A lighting MCB itself does not trip. I have two transformers and two light fittings and both combinations have the same result. If I take the load off the transformer, i.e. take the bulb out but leave the transformer connected the circuit it doesn't trip so no obvious short in the transformers.

The circuit is pre existing up to the transformer so I'm happy that's ok as it was switching mains voltage lights before without problems. It's a new build house so no old dodgy wiring.

Does anyone have any suggestions as to what may cause this?

Thanks.
Jas

 

[winston1]

RCCBs trip due to unbalance normally due to leakage to earth. I can only suggest leakage between the 240v side and the output side of your PWM power supplies (they are NOT transformers). When the lamps are fitted this enables the leak to earth.

Where did you buy the kit, a reputable UK manufacturer, or cheap import via an auction website?

Incidentally they are not low voltage. Mains is low voltage, 12v is extra low voltage.

 

[securespark]

(they are NOT transformers).

Not even the ones that say "TRANSFORMER" on the case???

You got more rabbit than Sainsbury's, me old china. Give it a rest.

 

[winston1]

(they are NOT transformers).

Not even the ones that say "TRANSFORMER" on the case???

Nope. That just shows the manufacturer does not know what they are selling and manufacturing.

 

[endecotp]

leakage between the 240v side and the output side of your PWM power supplies
When the lamps are fitted this enables the leak to earth.

Only if something on the output side is connected to earth, which it shouldn't be.

You might like to post some photos showing how you've connected the transformer and lamp to the cables, we might spot something unusual.

 

[Spark123]

I'd check the mains wiring is connected properly.
I can't see how leakage between LV and ELV sides of the transformer/psu could do this, you need a circuit for current to flow and the secondary shouldn't have any return path to earth. The transformer/psu should also provide adequate separation between primary and secondary for safety.
The reason that removing the lamp works may be as simple as the psu wont take any substantial load without a load on the secondary.

 

[EFLImpudence]

As you have two of everything, can you not determine what is causing the trip?

That is - one transformer and one bulb, then the other.



Am I right in thinking that removing a bulb will cause the transformer to not work, therefore no help?

 

[Spark123]

My guess is the psu is connected L to E, or L to the N of another circuit.

 

[ban-all-sheds]

My guess is the psu is connected L to E, or L to the N of another circuit.

The circuit is pre existing up to the transformer so I'm happy that's ok as it was switching mains voltage lights before without problems.

 

[securespark]

May I respectfully suggest you go off and write letters to every manufacturer of such-labelled devices letting them know they are mistaken.

Following is a definition taken from a dictionary for "transformer":

1. an apparatus for reducing or increasing the voltage of an alternating current.

2. a person or thing that transforms something.

 

[Taylortwocities]

It's Deja Vu time, again. *yawn*

 

[canduit]

Have you connected the 230 v supplt to the right end of the transformer? ie you haven't connected it to the 12 v output by mistake? Not sure what would happen if you did to be honest!

 

[canduit]

It's Deja Vu time, again. *yawn*

I'm sure I've heard you say that before

 

[Echo the husky]

Can you post any photos of the wiring connections?

 

[J5]

Hi

This is what I ordered... http://www.litecraft.co.uk/2-pack-of-over-cupboard-arm-light-satin-chrome ... they were actually Wickes branded when they arrived. They come with one 'transformer' but as I'm over two separate cupboards I ordered a second transformer matching the one supplied. Both have the same result. Semantics; I said Electronic Transformer as that's what it says on the tin, it's one of these infact http://www.energylightbulbs.co.uk/products/12v-transformer-et60. Not exactly a big toroidal . Definitely wired the right end as there is a moulded connector connected to the side labelled 12volt AC and a mains lead marked 230volt AC on the other.

I'll take some pictures next time I get a chance to climb up there and take a look.

Cheers for the input.
Jas