RCD for lights in one room keeps blowing.

[sadders]

An RCD for the lights in one of my rooms has just blown. The room has 9 low voltage halogen bulbs.

I reset the RCD and turned them on again. Pop and one of the lights flashes as the RCD blows.

I take the bulb out which has a spot of black charring on the back, change it and reset the RCD and try again. Same thing but now the light switch won't switch.

What's going on?

Ta.

 

[fireman22]

is there one transformer that feeds them all?
is it a normal light switch or a dimmer?

 

[sadders]

is there one transformer that feeds them all?
is it a normal light switch or a dimmer?

Each has a separate transformer (I think).

It's a normal switch which now won't switch.

 

[fireman22]

prbably one of the transformers has gone short circuit or melted the blocks behind and causing a short circuit and the short has in turn blown the light switch.

 

[fireman22]

you will need to drop each light and hopefully see melted blocks / cable and you will need to replace the switch after you find it, it probably wont be the light you saw coming on

 

[fireman22]

also do you mean mcb?

 

[sadders]

prbably one of the transformers has gone short circuit or melted the blocks behind and causing a short circuit and the short has in turn blown the light switch.

I am guessing it will be the transformer for the light that flashed (and charred) when they went out.

 

[fireman22]

no i doubt it will be that one, if you cant see something obvious it will be a transformers which will be a bit of trial and error unless you have a multi meter to check each one, look for melted cables first

 

[sadders]

no i doubt it will be that one, if you cant see something obvious it will be a transformers which will be a bit of trial and error unless you have a multi meter to check each one, look for melted cables first

Will change the transformer (I have a few spares knocking around) and switch then hold my breath / call out a professional.

Much thanks

 

[fireman22]

good luck, remember the switch may need changing if its "blown" and doesnt feel right when you operate it.
have any of the spots been going on and off by themselves pointing to a dodgy transformer?

 

[sadders]

Yeah, the switch as well.

No the lights have been fine. Not even a blown bulb for ages now. In another room a couple of transformers have blown. Might get round to doing them at the same time.

 

[fireman22]

were the lights on when it blew? this might point to a melted cable

 

[sadders]

They were.

If it is a melted cable is there an easy way of pin pointing where it is? If not, I presume it could be a big job to locate it.

 

[fireman22]

well it will have been melted by one of the lamps or a loose connection so it will not be too far from the light, but you will have to take down each light in turn i`m afraid

 

[Steve]

Please get rid of the downlights.

Extra low voltage doesnt mean extra low energy. A watt is a watt, regardless of the voltage.

You will always have these troubles with halogen downlights. Transformers are knocked out at a rate of thousands, quality control is poor for most brands.

The same goes for lamps - most people wreck transformers by fitting cheap lamps (B&Q own, Asda etc), which when they fail will pull a huge surge current which ruins the transformer and the switch, especially when its a dimmer.

If you really want to keep the downlights, use Osram or Phillips lamps (they are more expensive but they wont blow transformers as often).

Even better would be to use LED lamps, which last for decades and use only a few watts each. Change to mains voltage too, scrap the transformers, they are one more thing to go wrong, and you dont need them.