Lighting issue: At the end of my tether

[kingtubby]

Can someone give me any advice or should I just call an electrician and/or scream.

I am replacing a ceiling light with wall lights. When I removed the existing ceiling rose it was ok, except it just had 2 red wires (not 3, so I assumed it was at the end). After connecting my side-lights, nothing, except when I use the light switch it has slightly dims some other lights in the house. So after trying all combinations, I then retrieved the old ceiling rose from the bin, and connected the old light. Same problem, the light won't work and neither will the other house lights. I have disconnected and reconnected the switch, no luck. So I may have disturbed something, Is there anything else I should try before removing some more floorboards and checking the state of the previous ceiling rose? Any ideas gratefully received...

 

[Taylortwocities]

Guess you didnt keep a note of what went where before u disconnected the wires?
Is it only red wires at the rose or are there more? If so can you tell us exactly how many cables go to the old ceiling rose and what colour the wires are on each, also if any of the wires have coloured tape or sleeving on them.
May be able to help once we have that info.

TTC

 

[dingbat]

So I may have disturbed something...

Yes, you disconnected a working fitting without understanding how it worked. The problems are entirely of your own making. Read the posts in the 'Wiki' tab (top of the page) and you should be able to work out how you have wired some of your lighting in series.

 

[kingtubby]

In answer to the question, there were just two wires going into the rose (plus ceiling light), the two reds were on the Loop In centre connector then the black wires on the L & N.
I did take a note and when I reconstruct the ceiling rose wiring (but the light does not come on!), I get 240 Volts AC between each the L & Earth and between N & Earth when the switch is on. Between L & N, I get about 2 volts AC.
Does this help?

 

[dingbat]

Those two reds were, correctly, connected together and should remain so. One is the supply 'live' from the previous light in the crcuit, one of them is half of the switch cable. One of the two blacks is the supply neutral, the other is the other half of the switch cable - the 'switched live'. It should be appropriately colour coded to indicate that it's not a neutral.

But you are confusing your terms - the 'neutral' that is 240V above your earth is the switched live.

 

[jj4091]

From the readings you are giving you are losing a neutral somewhere, you should be reading 240v across the 2 black wires not 2v with the swich in the on position. Don't mean to insult you but is it possible you have screwed onto the insulation rather than the conductor, if not then I think that, yes, you are going to have to take up some floor boards.

 

[kingtubby]

Ok All, thanks for the advice, after a lot of fannying around

I have now tried the following, I bypassed the switch on the previous ceiling rose and the L & N read 240 volts AC. So I know 240V is going down the wires.

I then did the same on the problem one (so I know it is not a switch problem) and without a load, ie no 60 w light, it reads 240V. When the light is connected the voltage across L & N drops to 60 vAC (and hence light is quite dim)
This is interesting, is my light circuit on overload? Any ideas.

Happy new year to all, by the way

 

[bernardgreen]

I then did the same on the problem one (so I know it is not a switch problem) and without a load, ie no 60 w light, it reads 240V. When the light is connected the voltage across L & N drops to 60 vAC (and hence light is quite dim)
This is interesting, is my light circuit on overload? Any ideas.

Happy new year to all, by the way

A 60 watt load dropping the mains down to 60 volts means somewhere in the feed to that lamp there is a resistance. A resistance with the remaining 170 volts across it. (230 - 60 = 170) That resistance what ever it is will be dissapating heat, about 3 times as much heat as the lamp bulb is.

You need to get someone with the necessary skills and experience to find it and correct the wiring.

With a bit of luck it will be another lamp bulb which due to in-correct wiring is in series with either the live or neutral to the 60 watt lamp. At least if it is another lamp it does mean there is less chance of a dangerous hot spot under your floor boards.

Bernard
Sharnbrook

 

[Maboza-Ritchy]

Kingtubby
Without seeing it it sounds as though you have mixed up a swich wire & neutral(s).
This can result in some of your lights being connected in series - the fact you measure 60V with the lamp in circuit suggests that 4 lights are in series (4 x 60V = 240V). Do you have any other dim lamps in the circuit?

PS You will still measure 240V in an open - series circuit (lamp removed) as the volt drop in a circuit is proportional to the current drawn. The only current drawn when measuring voltage across an open circuit is what the meter draws.... and that is b*gg*r all. Hence 240V.

 

[kingtubby]

Yes you are correct, I get a couple of dimmer lights and one is activated by a switch that it is not connected (in normal circumstances to that light).

I assume the best way to solve this problem is to just identify the switch wires at each rose or junction box (with electricity off and measuring the resistance on the Volt-meter), in this lighting circuit.

Many thanks for your replies.

 

[Maboza-Ritchy]

Kingtubby
Firstly; each ceiling rose should have 3 x T&E cables except the last in circuit which will have 2.
Correctly terminated ceiling rose will have 3 reds in one terminal (Live joint)
2 blacks (Neutral joint) & 1 black (Switch wire joint).
The lamp is connected across the switch wire & neutral joints.

The easiest way to identify the switch wire is as follows:
Power switched off, disconnect and seperate the 3 black wires. with a meter on the OHMS range connected between the live joint and each of the black wires, ie check each black wire while someone switches that light switch on/off. The switch wire is the wire that reads 0 ohms while swich is on and infinity when switch is off. The other 2 blacks are neutral and should be connected into the neutral joint.

Please let me know if you need more info.

Steve