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Urgent - Advice with electrics

Discussion in 'Home Cinema Building DIY' started by spamboy, Jun 24, 2005.

  1. spamboy

    spamboy
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    Wondered if anyone could help out here. I've had some light wired up by my builders and I'm sure there's a problem.

    They've run a single cable from the switch out to each of the lights. There appears to be a live feed in the switchbox, which I've connected to one side of the switches, to the other side I've connected one of the wires running to the light, so Live gets to the lights.

    Problem is, there doesn't seem to be a neutral presented in the switch (there is one black wire, but it doesn't seem to go to earth or register any voltage. If I short the return wires from the lights to earth the lights come on and after telling the builder, that's exactly what he did.

    Now this seems dodgy as hell- if the connection to earth were broken, all of the lights (if earthed, would become live )

    Could you confirm that I'm correct in my thinking before I give him a good bollocking?

    Thanks,

    SB.
     
  2. louishm

    louishm
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    when you say single cable do you mean a grey twin and earth cable
     
  3. n2advnture

    n2advnture
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    I don't know how it is over there but here (US) we run a black (power), white (neutral) & a bare ground wire from the switch to the light.

    From the switch back to the panel, there is a black, white and ground. Then the panel is grounded to the earth.

    I would find out of your electrical panel is grounded. If it is, then the above scenario is how it should be done.

    Hope this helps.
     
  4. spamboy

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    Yes, it's a twin and earth cable, the earth is unshielded.

    Thanks,

    SB
     
  5. William

    William
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    Spamboy

    There a couple of ways (that I know) of wiring up lights.

    The most common is to have the live feed (ie L/N/E)from the consumer unit going to the light fitting. The Neutral is directly connected to the light, but the live is connected to s separate terminal. So effectively to switch on the light, the live feed terminal needs to be connected to the bulb. The technique is to use a normal twin and earth wire back to the switch. The red is connected to the live feed at the light fitting and the "neutral" connected to the live connection on the light. ie the black wire is not being used as neutral. At the light switch, the black and red wires are connected either side of the switch. It is normal to put a sleeve over the black wire to make it clear that it is not actually neutral.

    I can't see any case in which the earth should be shorted to live. If the wall box is metal for a light, I'm not sure if it needs to be earthed but if so, the earth on the twin and earth wire from the light fitting should be used to provide the earth continuity.

    This is obviously more complicated if you have 2 or 3 way switching for the light.

    The other technique is to bring the live feed to the switch. The live is switched but the neutral and earth need to be connected to the twin and earth going to the light fitting. In this case, I think it is normal to use a connector block to connect the neutral (it doesn't go through the switch).

    Not sure if this makes sense.

    I am not an electrician, so apologies for any errors in this.

    William
     
  6. louishm

    louishm
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    hi spamboy let me know exactly how many twin and earth cables are at the switch and how many lights are going in,, i am an electrician and maybe able to help. also if there is more than one light to be switched, how many cables are at the first one


    thanks
    paul
     
  7. Johnny Thunder

    Johnny Thunder
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    There should never be a neutral in a switch unless it is a double pole switch.
    Do not use this method in domestic circuits spamboy.
     
  8. louishm

    louishm
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    yeah, this is why i asked him if there was more than one twin and earth at the switch incase the builders had tried to wire it in two plate

    paul
     
  9. Sparky_S

    Sparky_S
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    the method we use here in ireland is to use 1.5 pvc/pvc wires to wire up lights, where as only live feeds, switchwires and earth (even if the box is plastic) are present in the switch box, the other method that does sometimes be used is the 3 plate ceiling rose method as explained above where as live neutral and earth go directly to the rose the center connector is the permanant live block whereas the feed to the switch goes and like wise the switchwire comes back up to the live connector linking to the bulb holder.

    the first method i said may be the method the builder is using, but he may be using your earth as a neutral path since your earth may be neutralised at your meter (im not sure if this netrualising method is used in england)

    AFAIK your wire colour code is red(live) Black(neut.) green/yellow(earth)
    while as here it is brown(live) blue(neut.) green/yellow(earth)
     
  10. John7

    John7
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    You should NEVER use an earth as a feed or return - it's potentially dangerous. The earth wire should not be bare - it should be sleeved (both ends) green/yellow and should be used even in a plastic box (a link earth should be connected between this and any metal switch plates)

    The cable that comes into the wall box should carry permanent live "Red" (new code brown) and the switched live (black with a red sleeve or blue with a red sleeve) which goes back to the light fitting. The neutral is unswitched and comes directly from the junction box in the ceiling to the other terminal of the light fitting. AFAIK this is the most common method of wiring lights in the UK (radial loop-in method)

    If you're really unsure -seek professional help

    Hope this helps -if you need a diagram LMK
     
  11. spamboy

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    Thanks everyone for your help, I've looked at some diagrams and it looks like he's screwed it up. They're sending in an electrician to have a look at it this week.

    Thanks again.

    SB
     
  12. louishm

    louishm
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    glad you eventually got it sorted
     

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