Help! Lighting!!

[scottmason]

Can anybody help? I am trying to fit a new ceiling light. On removal of the old ceiling rose i failed to take note of the connection.

Basically I have two wires coming from the ceiling. Both with a live (red) and a neutral (black) no earth. One i assume one goes to the mains and the other goes to the switch. I think i have identified the switch wire. So after blowing a couple of fuses I now have the red and black wires from the mains wire connected to the live terminal on the new light and the black wire from the switch connected to the neutral terminal on the new light.

I have light, didn't blow any fuses but i can't turn it off from the switch.

Any solutions!

 

[securespark]

See reference at the top.

 

[fubar]

Basically I have two wires coming from the ceiling. Both with a live (red) and a neutral (black) no earth. One i assume one goes to the mains and the other goes to the switch. I think i have identified the switch wire. So after blowing a couple of fuses I now have the red and black wires from the mains wire connected to the live terminal on the new light and the black wire from the switch connected to the neutral terminal on the new light.

No, you don't! You might think that you do, but you don't

Please carefully check the instructions for the light fitting. If the filling requires an earth, you must stop here and seek assistance from an electrician.

Okay, please make sure to turn off the appropriate circuits before each change. You'll additionally need a short (1cm or 2cm) length of red sleeving (perhaps heat-shrink) and either a choc block (terminal block) or ceiling rose.

1. Put all the wires from one cable into the choc block (each wire into a different row) and tighten the screws.
2. Connect the black from the second cable to the terminal marked N on the light fitting/ceiling rose and the red to the terminal marked L.
3. Fit the lightbulb, turn on the power and note whether the lamp lights or not. Turn off the power.
4. If the bulb lit, mark this cable "loop-in", else repeat 1-4 with the other cable.

Connect the two reds together using the loop-in part of the ceiling rose or a single row of choc block. Connect the black from "loop-in" to the terminal marked N on the light fitting/ceiling rose. Slip the red sleeve over the black wire from the other cable and connect this wire to the terminal marked L on the light fitting/ceiling rose.

Test and assemble. The second and third posts in the thread called "For reference" on this forum give some nice diagrams. In your case, the right-hand side of each diagram is what you have.

Regarding the earth - it sounds like your lighting circuit may have been installed prior to 1966. You must ensure that you only use fittings and accessories (switches, etc) that do not require an earth - e.g. non-metallic varieties or ask an electrician to provide new circuit protective (earthing) conductiors.

 

[scottmason]

Thanks Michael, i've sorted it but i have a metallic light and no earth, what can happen. i will change it anyway but just want to know for future.

cheers

 

[breezer]

what can happen.

the earth is there to protect you, if the light gets a short to live the light becomes live, anyone touching said light is now liable to electric shock, which can result in involuntary absence of life, or to give it its common name DEATH

 

[Damocles]

So what would you call voluntary absence of life?

Either electric shocks do not normally result in death or there is something people have been too embarassed to tell me.

This is not to say that they are a good thing.

 

[fubar]

So what would you call voluntary absence of life?

Suicide or euthanasia

My favorite sayings are "mild to moderate death", "terminal absence of life" and "death doesn't have to be fatal".

Either electric shocks do not normally result in death or there is something people have been too embarassed to tell me.

Entirely depends on your circumstances. Perhaps you have been lucky enough to have touched both live and neutral with the same finger, or been protected by an RCD or been wearing nice thick shoes, or have a particularly resilient heart?

I can assure you that 230V most definitely can kill - it is just a matter of how many milliamps are flowing through you and which parts of you they are flowing through. Luckily, most homes are designed to minimise the risk of receiving a fatal shock, which kinda brings us back on topic.

 

[breezer]

as you said (and for those who do not know) it is the current (measured in Amps, smaller unit mA milli amp) which actually kills, no one knows for sure exactly how low it is (lack of volunteers, i suppose) but everyone agrees it is about the 20-40 mA mark.

however the reason you may get an electric shock and just swear at the the time (no ill effects) is how much current passed through your body, everything has resistance (measured in ohms) the higher the resisatnce the less current (A) can flow, so if you are dry your resitance is very high.

The opposite is also true, if you are wet then your resistance is low, but also you must be in connection with earth (or neutral) in order for current to flow.

although the above is true, it is also true that if the voltage increases then more current current can flow, so although you could be dry, if the voltage is high enough, then enough current can flow through you to kill you.

 

[ohmygodwhathaveyoudone]

years ago i was papering my front room and wanted to paper behind the room thermostat so i very carefully unscrewed it and pulled it away from the wall about 1",then wollop got a massive shock through my right hand that travelled to my left nipple and got a nasty burn was also thrown across the room and ended up on the floor wobbling like a jelly with what felt like pins & needles all through my body.my chest hair was all burnt aswell.since then i've grown up & don't mess with electricity.
it was'nt nice.

 

[ban-all-sheds]

Well, serves you right for not being careful, doesn't it.

Re the V v A argument, I'm pretty sure it's the amount of energy you get that is the real decider. "Volts that jolts, mills that kills" is the mantra, but in reality you need both. - the human body can withstand 10's of kV if the current is low. Of course, you do need a high enough potential difference to get dangerous current to flow through the body, but IIRC there are documented cases of people killed by voltages normally considered "safe" (<50V).

 

[Damocles]

Point is though that normally people survive to tell their favourite electric shock stories.


Glad to know that suicide does not in fact constitute death.

 

[ban-all-sheds]

Point is though that normally people survive to tell their favourite electric shock stories.

Yo - been there, done that. Thank heavens for a very high Ze, I say...

 

[Lectrician]

I know a bloke who got a belt from the busbars inside a 3 phase mcb board, this was fed by about 2m of 35mm singles from the main mccb panel board, which was fed from a 800amp sub by paralleled 4*185mm (185 4 core alum concentric cable, all cores bonded into one lug, concentric un-used, but earthed).

He was thrown a long way, and said it felt as if someone had hit him in the chest with a sledge hammer. Lucky he was a fit lad.

 

[securespark]

DIE??? That'll be the last thing I do.......