Dimmer Switch Problems - Is it safe?

[np1664]

Hi, We have a dimmer switch (2 way 60W min-400W max) running 8 x 50W downlights (GU5.3) in the kitchen. Recently all but 2 bulbs have stopped working. I've replaced bulbs and switched the 2 which are working t the other positions but cannot get the other 6 positions working.

I opened up the dimmer switch. 3 wires come from the cable into the dimmer. A bare copper wire is connected to the dimmer back plate, a black wire to "C" and Red to "L1" There is also an L2 on the dimmer with nothing connected. There is no metal back box as the dimmer is screwed to a wooden panel with a whole dug out to accomodate it.

- is the wiring correct ...... and more importantly safe?

- if so what would cause 6 out of the 8 lights not to work (they worked fine in the past)

The dimmer has always buzzed relatively loadly

thanks for your help

np1664

 

[mikhailfaradayski]

HI NP,

No the wiring isn't right, the bare wire to the back plate should have green n yellow sleeve over it.

However, that isn't where the problem lies. As i understand it, irrespective of which fitting is in which hole, it is always the same 'hole' which doesn't work. If this is true, then you have a problem somewhere in the wiring between the 'holes' that work and those that don't.

Do you have a multimeter?

 

[flameport]

Most dimmers buzz, some more then others. They are usually louder with higher loads (yours is already at the maximum).

There should be a metal or plastic backbox, a hole in a wooden panel does not comply.

 

[Steve]

The dimmer is overloaded. You have 400 watts of halogen load. The dimmer is rated to 400 watts of plain tungsten filament load. Halogen has higher inrush than normal lamps.

GU5.3 - is this extra low voltage (12v?) if so, your transformers may be naffed due to the wrong type of dimmer being used. You have to match the dimmer and transformer carefully. Or use mains voltage and do away with transformers, then you can use energy saving lamps such as these
I just bought some for my bathroom. Very pleased with them. And you'll save much more energy than dimming.

 

[np1664]

Sorry I do not have a multimeter. We recently moved into this house so the dimmer and lights were already there. It was only after lights started failing (6 out of 8 so far) that I opened the dimmer switch to find the unsleeved earth and no metal backbox.

I am using 50W 12V GU5.3 halogen bulbs

If I go out and buy a higher rated dimmer eg 1000W max and put in a back box should I be safe and working? or is there something between the dimmer and the lights eg a transformer wich may need attention? I'm assuming this is in the kitchen ceiling (under carpetted floorboards upstairs)? In which case its best I call in a professional. thanks np1664

 

[Steve]

the transformer should be accessible. Pull down the downlights fittings (they are held in the hole with spring clips on the back of the ceiling), and pull the wiring gently, you may find a transformer near the back of each downlight. Change one, see if it sorts it (AFTER you change the dimmer - fit a normal switch for fault finding, 99p from B&Q). If new Tx does the trick, change the rest for dimmable Tx's, and make a note of whether they are trailing or leading edge - you'll need to match this to the dimmer.

Alternatively, instead of ferkin about with transformers, change all your lights for mains voltage. You'll need new fittings, but these are about the same cost as a new transformer. The benefit of mains voltage lights is you dont need to worry about dimming transformers etc.

 

[np1664]

Thanks Steve,

I'll first try changing the transformer (after changing the dimmable switch to a higher rating). I was not aware each light fitting would have a transformer if you pulled the cable a little more. I have just exposed enough cable to change the bulb in the past.

We don't really need dimmable lights in the kitchen (we inherited them) however would prefer to change to mains lights as a last resort as do like the look of recessed downlights.

- Can we go to mains and keep the same sort of light fittings in terms of looks ie mains run recessed downlights? you mentioned the megaman energy savers in your last email. Will these fit the same clip-in recess as I have for my GU5.3 bulbs, just would need to change the actual connector for a GU10 fitting?
- would we indeed need a professional sparky to change to mains?

cheers np1664

 

[mikhailfaradayski]

was i correct or not about the 'holes' always working?

There was no mention of tx's in the op, i assumed 230V, so could be the transformers, but feel its unlikely if at one instant 8 worked, then suddenly only 2 work. It might be different if one per day failed for six days.

Is there any discernable difference in the amount of buzz from the switch comparing 8 working lamps to 2?

Is the dimmer fully on?

 

[np1664]

I have 8 indivdual downlights, when you say "holes" do you mean each light? If so it is always the same 6 lights which are now not working. ie if I take the bulb from one of the 2 working fittings and attached to any of the 6 non-working fittngs then no joy.

The dimmer has always buzzed about the same whether all 8 were working or just 2.

One thing to add is that now only 2 are working, they tend to flicker. ie the light strength goes up and down randomly, irrespective of whether we turn the dimmer switch fully up or down, sometimes it settles down other times it goes on for quite a while.

Sorry didn't mentioned the Tx but as a total novice was not sure they were there.

The 6 lights did not fail all at once but went over a fairly short time 1-2 days. thanks np1664

 

[aptsys]

Alternatively, instead of ferkin about with transformers, change all your lights for mains voltage.

Don't do that. They're even ****tter!

 

[mikhailfaradayski]

Yea, sorry, from your OP i thought you had swapped the fittings around, not just the lamps. What i mean't by 'holes' was the position in the ceiling of each fitting. If you swapped the fitting around, but it was always the same positions that don't work, then i would suggest a fault with the wiring between the individual fittings.

I think you would benefit from a visit by an electrician if you don't have the facility to measure either voltage or continuity. Might cost a few quid, but it would get sorted quite quickly.

A contentious issue is mains against LV d/l's, FWIW i don't think theres a lot in it and i always fit mains unless LV is actually needed (less bits to go wrong without transformers)

 

[mikhailfaradayski]

The flickering you mention could be as a result of the TX being underloaded or a type not suitable for dimming.

 

[np1664]

I pulled out a bulb and here is what I found.

The bulbs (GU5.3 (50W/12V)) two thin pins connect to a small circular connector, this then has two wires running up from it, after about 2 inches there is a terminal block, this just seems to have two similar wires running out for a couple more inches into the ceiling space, I pulled the wires but couldn't get any more wire out of the hole or see any transformer connected. I tried this on 2 more bulbs/fittings and the same story.

Where are the transformers?
Why have a terminal block on each of the 2 wires running from the bulb and which only seem to connect two similar wires?
By terminal block I mean ones like thesehttp://www.screwfix.com/prods/32116/Electrical-Supplies/Cable-Accessories/Cable-Connectors/Terminal-Blocks-3A-Pack-of-10)

thanks

Np1664

 

[Steve]

The lamp connector comes with two thermally rated wires of a certain length, just enough to connect to the junction box on the fitting normally, or in your case, a flying terminal block.

Someone's hidden the transformers. Gits.

Did you take out the metal surround of the fitting? Like I said before, It just clips out, then you are left with a bare plasterboard hole that you might be able to see more with.

If you still cant get to any transformer on any fitting, get a digital camera and poke it up the holes, and take a photo back along where the wire runs. Do this for each of the fittings. You should find a/some transformer/s up there somewhere. I'm thinking maybe you have a big Transformer with multiple fused outlets. But this is unlikely.

A less high-tech method is to use a small mirror and flashlight up the hole.

 

[np1664]

Yes removed chrome fitting but this didn't give much more room to see anything more, tried camera can't get mine thru hole. will try mirror and light .... thanks for the suggestions.

Above the kitchen is the upstairs landing, carpetted but you can quite clearly feel a few wobbly floorboards. I suspect the transformer(s) are accessible from there. the landing does not cover the whole kitchen ceiling just a strip so if the transformer(s) are there then there must be running long wires to the fittings which are in the further reaches of the kitchen ceiling.

Slept on your idea of going to mains and more keen on it now.
- Can I keep the chrome and clip fitting with the GU10 megaman light savers? ie will they fit in the hole in terms of diameter and length, so you get the same visual effect as I have with the GU5.3 downlights?
- Is it a simple question of removing the transformer ( if I ever find it/them), and running the two wires to a new GU10 bulb fitting? or do you need different rated wiring? or a trained sparky?
- then replace dimmer switch with simple on/off switch?

thanks for your advice.

np1664