Lights keep blowing - Help!

[marksuf]

Hi there. I installed some new lounge lights yesterday (3 bulb chandelier type) as the wife has given me a headache about getting rid of the spotlights we inherited.

There are three sets of lights in the lounge/diner which work off a two gang brass dimmer switch. I fitted them all up and they worked fine, except that the dimmers won't dim. They will only come on with full power.

A couple of weeks ago, I changed the spotlights in the kitchen for a fluorescent light fitting. After carrying out this change all was well, and everything worked fine.

Tonight, we had the fluorescent light in the kitchen on as the same time as the new lights in the dining area. When the wife switched off the fluorescent kitchen light, the lights in the lounge/dining area blew. There was a bit of a bang from the lounge light fitting as it happened and the fuse in the main fuse box switched off. I took the light fitting off, and could smell a smouldering smell inside the light fitting. I checked all the wiriing, wired it all back up, and it did the same again when the kitchen light was turned off. What I dont understand is that there's a downstairs wc between the kitchen and lounge/diner, yet turning that on and off, or any other dowwnstairs lights doesn't cause a problem. It's just when turning off the fluorescent kitchen light. It has happened with two different dimmer switches, and the smell coming out of the switch seems to be coming from the live wire.

Independently, all the lights turn on and off fine, but it's only when the fluorescent kitchen light is switched off while any lights in the lounge/diner are on that these lights blow from the switch. The bulbs themselves aren't affected and will all work fine when the power is turned back on.

Can anyone tell me what may be causing this? Please let me know if you would need any more information to diagnose the problem.

Thanks for your help.

 

[marksuf]

Just to add, I don't know if I've wired the light switch correctly, although I'm pretty sure it's the same as it was before.

In the switch box, I've got an earth wire which I've connected to the earth connector on the light switch itself.

I've connected a blue wire (with a little red cover) to L1 on one of the gangs. I assume this would be the switch wire for the first set of lights.

There's a red wire which I've connected to the com connection. I have also connected another seperate wire into this connection which is connected to the com connection on the second gang at the other end.

Finally, there is a yellow wire, which I assume is the switch for the other set of lights into the L1 connection on the second gang.

The L2 terminals have no wires connected on either gang.

Is this the correct way to wire this up, or have I put a wire/wires into the wrong place?

As I said, they work absolutely fine on their own. It's only when the kitchen light is turned off that the light switch itself seems to blow.

 

[BS3036]

This is going to be a cr*p reply. We have some under-cupboard kitchen flourescent lights. They've been there a good twenty years. They're connected to our downstairs ring final. I once bought one of the first electronic timeswitches, which worked great and we plugged it in in the next room to the kitchen. One day we turned off the under under-cupboard kitchen flourescent lights, and the timer exploded. A real bang and a burn mark up the wall. I sent the timer back and the manufacturer sent me a new one.

A week later we turned off the under-cupboard kitchen flourescent lights and the timer exploded again.

This is not a good story because we still have the under-cupboard kitchen flourescent lights, and I haven't done anything about it.

The point is, I guess, that flourescent lights have a choke, which is a fairly large inductor, which is an electical component which, once current is flowing in it, wants to keep current flowing, even if that means producing a really large voltage to make it happen.

If you switch off current flowing through an inductor, a large voltage spike can appear, which can damage other connected devices.

A properly designed flourescent light should have other components to prevent this problem from happening.

I am guessing that in your case (and possibly mine) these other components are faulty or not connected properly.

So I would suspect the flourescent light and try changing it.

 

[marksuf]

Thanks for your reply, but I still think it's something I've done this weekend. I take your point about fluorescent light fittings, but I put that light up a couple of weeks ago and it's been fine up until now.

I haven't conciously taken notice of having switched off the kitchen light while any light has been on in the lounge/diner, but I'm sure we must have done at some stage in the last two weeks and there hasn't been a problem. I don't know if it makes a difference, but there is also an extractor fan connected to the light fitting in the kitchen.

Even last night after the new lights were put up, we didn't have this problem. This morning, I changed to non-dimming dimmer switch for a plastic rotary one which doesn't have the push on/off feature, and this was the first to blow this evening when the kitchen light was turned off. I replaced it with the original brass one, but that one seems to blow too when the fluorescent kitchen light is turned off. It's all really frustrating, because all the lights work fine on their own. I doubt there's any problem with the wiring inside the new lights themselves as they all turn on and off with no problems, it's just the lounge light switch which blows each time the kitchen light is turned off. Aaaarrrrggghh!!

If all else fails, I'll have to call in an electrician.

 

[Veglen]

Have you tried replacing the two gang dimmer switch with a normal on/off switch?

Sounds like you have connected something wrong somewhere! Do you have the use of a multimeter?

You would also need to know how to use it on the voltage and continuity ranges?

I’m thinking you may have a live / neutral short through the dimmer switch. Not quite sure how the problem only shows when the kitchen light is switched off though! I could be totally wrong but suspect the fault maybe due to possible lights being in series with the dimmer switch some how.

V

 

[ban-all-sheds]

Let's see...

This says that you didn't wire it up properly in the first place:

I fitted them all up and they worked fine, except that the dimmers won't dim.

Just to add, I don't know if I've wired the light switch correctly

and that as well as changing the lights you fiddled with the switch.

This says that you've wired it up with a lot of assumptions about which wire does what:

I've connected a blue wire (with a little red cover) to L1 on one of the gangs. I assume this would be the switch wire for the first set of lights.

There's a red wire which I've connected to the com connection. I have also connected another seperate wire into this connection which is connected to the com connection on the second gang at the other end.

Finally, there is a yellow wire, which I assume is the switch for the other set of lights into the L1 connection on the second gang.

The L2 terminals have no wires connected on either gang.

And given the colours involved they aren't the most obvious assumptions to have made.

This says that you don't know how the switch was wired before:

Is this the correct way to wire this up, or have I put a wire/wires into the wrong place?

And this says that following a second bit of work you've got a serious fault occurring:

As I said, they work absolutely fine on their own. It's only when the kitchen light is turned off that the light switch itself seems to blow.

As well as having and knowing how to use a multimeter, you'll also have to learn how lighting circuits are wired and you'll have to trace and identify all of the cables to and from the switches and lights and make sure you know which one is which.

Or you need to get an electrician. Which mightn't be a bad idea anyway, as all these repeated bangs and smells of burning mean something might be permanently damaged.