After Fitting New Ceiling Light Other lights Dim & Flick

[frattonstation]

Help, electrical novice here !
I have just wired in a new light upsatirs which works fine.

Only problem is since I wired in this light all the other lights upstairs are very dim and flicker a bit, cue nervous laughter !

When connecting the light I wired the black live to the brown of the light, two other blacks to the blue wire and earth to earth. the three red wires from the ceiling, I isolated in a block of their own.

Is this correct or is it the root of my dim light problem ??

Please help !!!

 

[felix]

Your wiring is correct, always assuming that the old rose was wired correctly to start with! You most likely have a bad connection in there. It will either be in the choc block or the neutral terminal but check them all. Look for blackened wires and melted insulation.

If you dare, leave the cover off, stand well back and put the power back on. Switch on your other lights and you might see sparks coming from the bad joint. Don't forget to switch off again before you fix it!

 

[frattonstation]

Thanks for your reply I shall try this when I get home tonight !

I've turned the mains off so I have got a home to go to tonight just to be safe.

 

[felix]

Crumbs, that was a quick turn around. This is like being on ICQ! Turning off the mains was a wise move. Bad connections can start fires. You sound like one of those peolple who can work around a live terminal because a little bit of your brain is constantly aware of its existence. Ever thought of fixing particle accelerators for a living?

 

[frattonstation]

just common sense too me !!
as for particle accelerators....I say just add a teaspoon of salt & sugar and stir well. I prefer hundreds and thousands though.

 

[felix]

But you can have a lot more fun stirring helium ions. I think we're getting a bit off topic here. Time to quit before the moderators kick us off. Good luck with those bad joints.

 

[frattonstation]

Tried all the connections...all seems well..no burning or damage.

What I have noticed, that I didn't before, is that when I switch on the other lights on the same floor that the lights i have fitted actually come on very dimly...can anyone help ?

 

[felix]

OK, I can see one wiring mistake which fits all the known evidence. Three black wires came out of the original fitting. I think you have them mixed up.

One of them is switched live from the light switch. This, I suggest, you have connected to the neutral return for the rest of your lights, and also to blue in the new light. The third black wire, which you have connected to brown on your new light, is, by process of elimination, neutral from the consumer unit.

With this circuit, all power going out to the other lights must come back through your new light. The route is live feed - other lights - blue wire - new light - brown wire - neutral return. I assume your other lights are low power fluorescents (hence the flickering) and your new light is a filament bulb.

The new light works because its switch is still in series with it. The rest of the lights are effectively connected across this switch. Do they work at all if the new light is switched on? If no, QED, if they do then it's back to the think tank.

WARNING: There are three ways to pair up two black wires. One will work, another you have (I think) but the third will put your switch straight across the supply. I saw this happen a long time ago. Classic boo-boo, switch and lamp wired in parallel. It didn't just pop the lighting fuse; it blew the big one as well!

 

[plugwash]

hmm never heared of a lightswitch doing that before.

what rating was the service fuse and was the lighting cuircuit especially short or something?

 

[felix]

It was long ago when I was a spotty teenager so my memory is a bit hazy. My father wired it up and was a bit surprized when the light came straight on - so he tried to turn it off!

The wiring was really old stuff, now thankfully replaced. It dated from the days when you plugged your iron into an overhead light socket. We even had a special adapter for it so you could have the light as well. I had a friend up the road whose kitchen boasted a 15 amp three pin socket. To us it was a brute of a socket and the only one in the house. I have to assume from all this that service fuses in those days weren't very big.

Back to the lighting problem ---

IF my hypothesis is correct you need to work out which black wire is which. The one on its own will be the neutral return to the consumer unit. Remove each of the other two in turn and isolate it in choc block. One of these two possibilities will make your new light, but not the old ones, work properly. Now connect the free wire to the other side of the light and everything will work, except for your light wires being the wrong way round. You can easily put that right.