Electrical question (light wiring)

Discussion in 'General Chat' started by chump, May 2, 2016.

Tags:
  1. chump

    chump
    Well-known Member

    Joined:
    Nov 11, 2008
    Messages:
    1,514
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    116
    Ratings:
    +1,448
    Note that at this stage I'm having an electrician take care of this as I don't want to take any chances but was hoping someone would try to explain to me how this works just to see if I'm on the right track?

    Removed a ceiling rose and stupidly forgot to write down what was connected where.

    I understand that one of these 3 cables contains a switched live. I have a multi meter which I could use to test to found out which one. I'm not going to chance it - just wanted to see if i've got it right in my head. There is another ceiling rose on the other side of this room connected to the same circuit.

    Photo below shows the wiring:

    20160502_092217.jpg

    And i found this diagram:

    ceiling_rose.jpg

    My understanding is:

    - Find the switch live (test between red and black wires with light switched on until voltage detected on multi meter set to 600 AC). Wire the black cable of the switch live into the live on the light fitting.

    - Wire the red cable from switch live and the remaining red cables into a terminal strip.

    - Wire the black neutrals between lights (remaining cables that are NOT the switch live) into a terminal strip then subsequently into the the neutral on the light fitting.

    - Make sure all earth cables are grouped into a terminal switch then subsequently into the earth connection on the light fitting.

    How does that sound? Again - I'm not attempting this. Just want to see if I've got the theory correct. Electrician is attending! :D
     
  2. RBZ5416

    RBZ5416
    Distinguished Member

    Joined:
    Nov 4, 2002
    Messages:
    18,605
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    166
    Ratings:
    +6,953
  3. wilbanat

    wilbanat
    Distinguished Member

    Joined:
    Sep 25, 2009
    Messages:
    7,643
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    166
    Ratings:
    +9,486
    Nope ;)
    You will have no voltage on the switch live, with the wires like they are in your picture you would (power off) check for continuity to find the switch cable.
     
  4. chump

    chump
    Well-known Member

    Joined:
    Nov 11, 2008
    Messages:
    1,514
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    116
    Ratings:
    +1,448
    Thanks. That does actually make more sense and sounds a lot safer too. Not that I'll be risking it!
     
  5. IronGiant

    IronGiant
    Moderator

    Joined:
    Jun 7, 2003
    Messages:
    63,564
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    166
    Location:
    .
    Ratings:
    +42,599
    Rule No. 1. Never assume anything is wired up it should be :D
     
    • Like Like x 1
    • Agree Agree x 1
    • List
  6. wilbanat

    wilbanat
    Distinguished Member

    Joined:
    Sep 25, 2009
    Messages:
    7,643
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    166
    Ratings:
    +9,486
    I remember my Brother decided to change a light fitting once as he had watched me do his other ones and thought it looked easy...I ended up there late at night in the pitch black trying to rectify his mess.
    Nothing like working on electrics by candle light :laugh:
     
    • Like Like x 1
    • Agree Agree x 1
    • List
  7. chump

    chump
    Well-known Member

    Joined:
    Nov 11, 2008
    Messages:
    1,514
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    116
    Ratings:
    +1,448
    It's funny you should say that. It's probably my mind playing tricks on me but I swear when I took the old rose light off the 3 earths were twisted together, the 3 black cables twisted together and the 3 reds twisted together. And each twisted trio then inserted into the relevant connections on the old light......??
     
  8. wilbanat

    wilbanat
    Distinguished Member

    Joined:
    Sep 25, 2009
    Messages:
    7,643
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    166
    Ratings:
    +9,486
    No it wasn't, it is your mind :smashin:
    Well look at your diagram again as that is a classic way to wire a light.
    You have a cable that brings the power to light
    a cable to take power to the next light
    a cable to nick the power and feed the light bulb (switch cable)
     
    Last edited: May 2, 2016
  9. ATC-XTC

    ATC-XTC
    Standard Member

    Joined:
    Aug 6, 2006
    Messages:
    48
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    8
    Ratings:
    +18
    You seem to have a good understanding of what's involved.
    This is how I'd do it.

    After ensuring the breaker supplying the lighting circuit is switched off, check with the meter that the power is actually off!

    It's easier and safer to identify the switch circuit with the multimeter set to resistance or continuity, operating the switch will cause a tone from the meter when set to continuity mode, or a short circuit ( zero ohms) when on resistance mode.

    When you've identified the switch cable mark the black wire with brown sleeving or tape, this is the live to the lamp, all the reds go together and the remaining blacks go together linking to the lamp neutral.

    Hope that Helps

    Crocodiles posted a helpful link while I've been typing this.
     
  10. chump

    chump
    Well-known Member

    Joined:
    Nov 11, 2008
    Messages:
    1,514
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    116
    Ratings:
    +1,448
    Thanks! I was close then with the theory but no cigar :D
     
  11. its_all_Greek

    its_all_Greek
    Distinguished Member

    Joined:
    May 8, 2009
    Messages:
    4,700
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    166
    Location:
    Nottingham
    Ratings:
    +2,515
    Although normally correct it is possible this is the end of line fitting and the third cable goes to a second fitting off this switch.

    with regards ATC's post...

    A multi meter is not recognized as a suitable means to prove a circuit is dead, however i appreciate that most homes will only have a multi meter if anything, so please prove that your meter is working before and after testing the circuit is dead.
     
    Last edited: May 2, 2016
  12. wilbanat

    wilbanat
    Distinguished Member

    Joined:
    Sep 25, 2009
    Messages:
    7,643
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    166
    Ratings:
    +9,486
    Yeah I was trying to keep it simple :p
     
  13. Sonic67

    Sonic67
    Distinguished Member

    Joined:
    Sep 14, 2006
    Messages:
    42,019
    Products Owned:
    11
    Products Wanted:
    1
    Trophy Points:
    167
    Location:
    Home
    Ratings:
    +19,701
    Try it and every time you operate the switch you'd blow the fuse as you had connected a live directly to the neutrals.

    Look at your own diagram.
     
  14. Sonic67

    Sonic67
    Distinguished Member

    Joined:
    Sep 14, 2006
    Messages:
    42,019
    Products Owned:
    11
    Products Wanted:
    1
    Trophy Points:
    167
    Location:
    Home
    Ratings:
    +19,701
    Actually there is another way of doing it.

    Take a cable from a light or the board or a socket or whatever, so you have a live feed with a neutral, loop the cable in and out at the light switch.

    Don't break the neutral but break the live so it runs to the top and bottom of the switch. Run that cable to the light. Now when you trigger the switch the light comes on. The other two cables could run to two other lights which come on at the same time.

    If the lighting was wired in this way then it would be that all the reds, blacks etc would be together.

    There is different ways of doing anything.

    Note this is unlikely but possible.

    Top tip. Before doing anything I photograph and label and draw little pictures of what I have before I started. Worse case scenario I can return everything back to the state it was in before I started.
     

Share This Page

Loading...
  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice