A plea to people changing light fittings!

[securespark]

Been out this morning to a job where customer told me her newly-replaced light fitting didn't work.

She told me it stayed on all the time.

When I looked at how it was wired, there were three conductors present at the ceiling position:

switched live

2 x neutral

The switched live she had put in the loop terminals on its own.

The neutrals went to either side of the lampholder.

It worked, but would not switch off....

PLEASE MAKE A NOTE OF WHAT WIRES GO WHERE BEFORE YOU DISCONNECT!

 

[ban-all-sheds]

The neutrals went to either side of the lampholder.

It worked, but would not switch off....

They can't both have been neutrals then....

 

[plugwash]

provided other lights beyond it were turned on yes it would light albiet no at full brightness.

 

[securespark]

Yes they were both neutrals, Ban.

When both blacks were wired to one side of the l/h and the sw live to the other, it worked as it should.

In fact, the next door fitting in the kitchen was the last on the circuit, and its switch was on, so that rendered one of the netrals effectively live.

 

[ban-all-sheds]

Yes they were both neutrals, Ban.

When both blacks were wired to one side of the l/h and the sw live to the other, it worked as it should.

But you said "The neutrals went to either side of the lampholder", not to one side.

In fact, the next door fitting in the kitchen was the last on the circuit, and its switch was on, so that rendered one of the netrals effectively live.

If both blacks were neutral, and both were wired to the same side, and then you somehow made one of the neutrals live, wouldn't you get a bl***y great bang?

 

[Adam_151]

I think the situation is here that there was neutral looped through the fitting, and switched live from the switch, obviously both neutrals should go to one side of the lampholder and the switched live to the other, which was how SS wired it, but the house holder had managed to get sw live connected to nothing, and neutrals to each side of the lampholder, so the fitting was wired in series with the rest of the lighting circuit, and as long as at least another fitting in the house was on, it would light dimly and the switch would do sweet FA.

 

[Big_Spark]

BAS, think of Christmas Tree lights, so long as the lamp in the fitting is the GLS tungsten Filament type, then it will complete the circuit as far as the neutral is concerned, it would be like a fusable bridge in the neutral to all intents and purposes. As current flows from Neutral to Phase, a current will flow through the filament of the lamp, equally there would be a potential difference across the lamp as a result. This potential difference coupled to the current flow in the neutral would cause the lamp to glow, as has been mentioned, not at full brightness in all liklehood, but it would appear on so long as current flowed on the neutral and the potential difference existed.

 

[securespark]

In fact, the next door fitting in the kitchen was the last on the circuit, and its switch was on, so that rendered one of the netrals effectively live.

Adam's got it bang on. Ban sorry for the confusion- the neutrals were indeed connected to either side of the lampholder by the h/h. I changed the wiring to put the two neutrals on one side and the sw live on the other.

Because the next door light was the last on the circuit and its switch was on, the neutral to that light was effectively live, giving a "live" and neutral supply to the lamp.

Jim - it was pretty much full brightness, having seen the lamp lit up. It wasn't very dim at all. Can't explain that, unless the fact that there was only one lamp for the current to travel through had anything to do with it.

 

[plugwash]

what was the other fitting it was placed in series with like

if you put a 100W bulb in series with say a 500W one (or a paralell group that adds up to that much) then the 100W one will get most of the power.

 

[securespark]

A 200W GLS.