The introduction of Spot lights

Discussion in 'Electricians' Talk' started by jfk, Nov 29, 2003.

  1. jfk

    jfk New Member

    I would like to put 6 spot lights in my launge instead of the central light arrangement. Can I power all the spots off the original light cable or do I have to rewire?

    Thank you for the advise in advance.
     
  2. Tommy Walsh

    Tommy Walsh New Member

    No, providing the cable is 1.0 mm and the insulation is in sound condition.

    I have upgraded rooms with a single pendant fitting with up to 6 halogen 35w bulbs and it is fine.
     
  3. sparky (Original)

    sparky (Original) New Member

    just go from one spot to the next using a junction box.
     
  4. Ben

    Ben New Member

    Are you allowed to loop from spotlight to the next spotlight and so on? Or would you recommend using junction boxes because they are easier or safer?
     
  5. Milton Bradley

    Milton Bradley New Member

    Use a junction box - otherwise the limited space in a spotlight will be very hard to wire - anyway the heat generated by a spotlight will do more harm than good to overcrowded cables.
     
  6. sparky Si-Fi

    sparky Si-Fi Screwfix Select

    Just wondering JFK (firstly I thought you got shot in Dallas? ....oh well whatever)Am I right in saying the spotlights you are intending to fit are low voltage (230)they probably are mind, or SELV supplied from a BS 3535 transformer,its you have not mentioned this in your post,if they are,we could be talking a totally different way here.

    Its such that SELV lighting is proving very popular due to its superb lighting characteristics
     
  7. jfk

    jfk New Member

    Thanks for the words of wisdom everyone. Much appreciated. With regards to the type of lights (Sparky), that was my next challenge - which lights to use. Any ideas?

    Reading the responses, I am now motivated to also install them in the hallway. My concern is that the ceiling is of the old traditional type and cutting a hole will be tricky. Ideas on how best to do this would be welcomed.

    Thank you in advance.
    What was that comment.... killed in Dallas. In today's soaps nobody dies. Look at Denis in Eastenders.
     
  8. supersparky

    supersparky New Member

    if you mean fitting them in lathe plaster ceilings, rip it down lol
    also use low voltage
    on a 1:1 transformer to light ratio
    BR
     
  9. unphased

    unphased Screwfix Select

    Just a word of caution. The regs require that when working out current demand on a lighting circuit each light has to be assumed to be 100W, irrespective of whether it is a lower wattage. Therefore, you are replacing 100W with 600W. The maximum load on a 1.0mm2 cable is around 13A. You are okay as far as cable size is concerned but you might need to upgrade your fuse to 10A if number of lights exceed around 12 (1200W) (ie twelve light fittings). 1200W/230V=5.2A. Hope this helps.
     
  10. supersparky

    supersparky New Member

    also if put on a10amp you must upgrade to 1.5mm

    BR
     
  11. jfk

    jfk New Member

    Supersparky, how have you arrived at the need to upgrade the cable to 1.5mm? sorry but I am a novelist here.
     
  12. supersparky

    supersparky New Member

    if you use a 10amp breaker for lighting circuit it must be 1.5mm 1.00mm is only used on 6amp and it was a reply to the comment by unphased who suggested you upgrade to 10amp mcb

    BR
     
  13. unphased

    unphased Screwfix Select

    Apologies for any confusion jfk..supersparky absolutely correct in that 10A MCB would force uprating of cable. Best thing to do here is count exactly how many individual lamps you would have on the affected circuit and if you have more than 12 I would recommend replacing the wiring with 1.5mm and using 10A MCB...

    RSS
     
  14. supersparky

    supersparky New Member

    heh heh :)
    but like unphased said each fitting should be assumed to be 100w each, dont know what the situ is at the moment but i only load each lighting circuit at 6amp up to 1000w max for future expansion if this is the case then it might be worth just instaling a new 6amp supply to the lights seems exessive but better then re wireing ;)

    BR
     
  15. ban-all-sheds

    ban-all-sheds New Member

    if you use a 10amp breaker for lighting circuit it must be 1.5mm 1.00mm is only used on 6amp and it was a reply to the comment by unphased who suggested you upgrade to 10amp mcb

    I'm curious about this - 1.0mm cable is rated at 14A. To be sure you might need 1.5mm if voltage drop or other derating calculations show that 1.0mm isn't enough, but why is there a blanket restriction of a 6A breaker on 14A cable?
     
  16. supersparky

    supersparky New Member

    well i have already explaned this before so this time im going to copy it straight out of the 16th ed;
    "......consider a cable system rated at 30A and protected by a mcb type c rated 32A,...Shows that a prolonged over load of arround 38amps will open the breaker after about two and a half hours" which is enough to cause damadge to the cable, on a lighting circit 4 amps (before de rateing and correction factors) is simply not enough

    BR
     
  17. jfk

    jfk New Member

    Thanks unphase for the advice, and everyone.
     
  18. jfk

    jfk New Member

    Thanks unphase for the advice, and everyone's input.
     
  19. ban-all-sheds

    ban-all-sheds New Member

    [<u>supersparky</u> well i have already explaned this before so this time im going to copy it straight out of the 16th ed;
    "......consider a cable system rated at 30A and protected by a mcb type c rated 32A,...Shows that a prolonged over load of arround 38amps will open the breaker after about two and a half hours" which is enough to cause damadge to the cable, on a lighting circit 4 amps (before de rateing and correction factors) is simply not enough
    ]

    But here we're talking about a 14A cable and a 10A breaker, not a situation of a breaker rated above that of the cable.

    Using your 4A overload figure, that makes 18A, and a 10A type B or C will trip after about 10 minutes - wouldn't have thought that would damage the cable.

    I'm not trying to argue with you - would just like to understand more.
     
  20. supersparky

    supersparky New Member

    correction factors for 1mm cable:
    in conduit or in thermal insulation brings the rating to 11amps it only meets its max of 16amps when clipped direct
    then assume that it runs with a bunch of cables, it will undoutibly venture into the loft and near ch pipes at some point
    now take into account that 14 amp is the MAX recomended current. soon adds up then that 4amp overcurrent makes more of a difference 4 amp and also take into account that the circuit maybe long, earth csa is only 1mm
    so by the time you have applied all that your rating goes down to about 9amps probrably(i know it dont all have to do with tripping breaker but what if the cable at the start of the run has to have all of these applied?and the circuit is at its full 2400watt load then with a fault of 6 amps so we are now at say...16 amps through a cable de-rated to 8amps(in the worst case)? then what if there is already another circuit opperating near its max... than the cable is already warm... then if this is a regular occourance you get regular warming and cooling of the cable, it will lower the life.
    either way it is good practice and i will continue recomending it, im not a fan of 1mm, if you decide 1mm is fine then so be it, it is your name that goes to it and if the breaker trips and the coustemer feels the cable and it is warm......alarm bells start ringing and you would be forced back to change it, then your out of pocket

    BR
     

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