Kitchen Downlighters

[BazzaS]

In my kitchen I have 6 rows of 12V 20W downlighters.
In some rows ther is only one light and in others there are 3 lights.
They work via a dimmer switch.
After the lights have been on for a while, a row (one light) and the adjacent row (three lights) go out. The others remain on.
The rows that go out are always the same and are neither the first nor the last in the sequence of rows (hope all this is clear ?).
None of the lights that go out have a transformer attached (which I thought could be the problem).
Help - am at my wits end as to whats going on - or rather whats going off !

Can anyone please advise me.
Thanks
Bazza

 

[breezer]

i bet there are transformers (or one transformer) since you said they are 12v, how else will they work on 230v?

there must be a transformer some where, either that or they are not 12v

 

[BazzaS]

Thanks, but.....
Yes they are indeed 12V. I would have expected a transformer attached somewhere to the wiring of the offending lights but there isn't one so attached. Where else might it be.
And if not attached to the offending lights why do only these go out ?
And yes I've checked cabling for fit and tightness.
Bazza

 

[ban-all-sheds]

Thanks, but.....
Yes they are indeed 12V. I would have expected a transformer attached somewhere to the wiring of the offending lights but there isn't one so attached. Where else might it be.

Think about this - the transformer(s) have to be somewhere - if you follow the cables back then sooner or later you must find them...

 

[theshogun]

Is the space above the kitchen accessible with out lifting floor boards?
How many lights are there?
The transformer may be sighted at a light at the end of each row and used to control that particular row of lights.
When you have removed the lights ,what do you find attached? ie heat proof flex to joint box then to normal flat twin and earth cable which connects to next light .

Have you tried swappimg the offending lamps to another fitting just to eliminate them as a possible cause?

Have you checked all the lamps are 20w and some have not been replaced with 35 or 50w lamps and might be overloading the transformer.

 

[fireman22]

if i installed these lights, and obviously there is a transformer feeding the lights that are going down, it must be too large to fit through one of the light holes so i would have installed it above kitchen in a cupboard? in airing cupboard, in attic even, there may be a loose floor board somewhere with trans under it. i doubt if an electricain would have installed it somewhere inaccessable

also if you remove dimmer and replace it with a normal on off switch this will eliminate faulty dimmer i.e. overloading / getting warm and bad connection on one of the out going cables from the dimmer, assuming there is more than one cable leaving it

___________________________
moderator

please note 10a

 

[Jel]

When you do find this transformer which you should start by looking where you feed originates from, one way is to trace your switch wire from the socket/switch if possible, you will eventually discover the transformer. When you do find it look on the transformer for the rating some start from as low as 20 and go up to 60va whilst others go upto 100-210va and there are many inbetween. Then add you your total bulb load i.e 20w x 5 and make sure it fits inbetween the transformers range. (also check the bulbs are 20w usually some print in the reverse of the bulb. Secondly not all transformers are designer for dimmers something which you usually discover in the instructions or on the pack (before installing) and finally loose connections (although flickering would normally occur).
If the transformer appears to in range try changing for a cheapish dimmer (£8) especially if you had s/steel so as not to waste costs (make sure it is dimmer compliant)

 

[mapj1]

Could be 2 or more transformers, they should have a thermal trip built in, one may be mounted in such a way it overheats and shuts down until they all cool off...

Try a mirror and a torch bulb on a stick for seeing where things go in 'inaccessable' places - think dentist!

(and dont rule out the possibility it may well have been accessible to the sparks, but then the new lino was laid in the room above !)

 

[delmel]

One thing is certain there is a tranformer or more than 1. First question do you know who fitted them, if so they may recall how they did it. Sound like perhaps the thermal cut out it operating on the transformer. Is ther lots of insulation above the ceiling. Transformers can be very small now.

 

[BazzaS]

Thanks people for all your advice/help.
Found two transformers and replaced them - but no effect.
Then.. I got really annoyed and pulled out all the wiring that I could and found the transformer that links with my offending set of lights ALSO served the downlighters for the kitchen cupboards!! These were working OK so I never initially looked at this circuit. Thanks Jel for suggesting I count up what's (watts) on the circuit(s).
Anyway, it now serves only the cupboard lights and I've added a transformer for my offending set.
So far all lights have remained on and I hope this is the solution.
Regards
Bazza.

 

[mapj1]

sounds like thats it then. Let us know if it isn't (and make a note of where theose transformers are and leave it in an envelope by the fuse board for future reference.)