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Adding a switch and light to an existing circuit

Discussion in 'Electrics UK' started by Rich0056, 29 Jun 2021.

  1. Rich0056

    Rich0056

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    Hi,

    In my loft I have two daisy chained lights installed by the previous owner, they just had a long cable and a 3 pin plug on the end that I had to drag out of the loft and plug into a socket on the stairs every time I wanted to go into the loft.

    I decided to add a junction box and a switch on an existing lighting circuit in the loft so I can just switch the loft lights on and off as I go in. I turned the power off at the breaker, cut into the circuit (after checking with a voltage detector) and installed the junction box as per the attached picture. I've checked it a number of times and I can't see what I've done wrong. With the power back on, the light in the room below will not go off unless I turn the switch in the loft off. With the switch in the loft on both lights are on.

    With the loft switch off, the light in the loft is off and the switch works for the room below.
    With the loft switch on, the light in the room below is constantly on and the loft light is on.
    With the room light off, the loft light works but turns the room light back on.

    I'm stumped, so any help or advice would be greatly appreciated.

    Cheers!
     

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  2. winston1

    winston1

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    The cable you “cut into” seems to have changed its colours after the cut. How did it manage to do that?

    Magic aside I guess you have cut into the switch drop. This would put the two lights in series. With old style incandescent lamps they would be dim but modern CFL’s and LED’s often still work around half voltage without noticeable dimming.

    You also forgot to sleeve the bare earth wire.

    Do let us know about the magic cable changing colours.
     
    Last edited: 29 Jun 2021
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  4. ETAF

    ETAF

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    Not qualified, just a DIYer, who has done a bit of electrical work and trained E&Eeng many years ago

    you sure you have cut the power line and not a switched line ?
    Which cable that you CUT as there appears to be earth sleeving on some but not all the cables, and different cable types - maybe just the image.

    Is the Junction Box available near the Main Light itself, OR in the Ceiling rose for the light
     
  5. Rich0056

    Rich0056

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    Thanks for the replies.

    There was very little slack on the cable so I extended it with an inline junction box and some new cable.

    Makes sense on the switched cable. Most of the loft is boarded and it was the only cable I could find that was accessible. I've removed the junction box and re-connected the original cable with the inline junction box so will have to see if I can locate a power line, although not sure how I will be able to do that!
     
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