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How do you find out which wire is live?

  • 01-05-2012 11:57PM
    #1
    O'Prez
    Registered Users, Registered Users 2 Posts: 676 ✭✭✭


    Hi everyone. I'm putting in some new socket plates and some new ceiling lights at home. Some of the old plates I replaced were marked N and L so that was handy enough but some others aren't. The ceiling lights are another story. I'm replacing the standard bulb/lamp shade set up with chandeliers and need to know which wire coming from the ceiling is the live one. There are two...both grey. What tool would you recommend for testing which is the live one? Thanks :)


Comments

  • #2
    ted1
    Registered Users, Registered Users 2 Posts: 24,300 ✭✭✭✭ted1


    oH dear, best to get a qualified sparks.


  • #3
    beazee
    Registered Users, Registered Users 2 Posts: 1,343 ✭✭✭beazee


    Z0MGJ.jpg
    Mains tester? €2?


  • #4
    fasttalkerchat
    Registered Users, Registered Users 2 Posts: 5,652 ✭✭✭fasttalkerchat


    Don't use your tongue!


    OP?




    You there?





    ****! We lost one.


  • #5
    peckerhead
    Registered Users, Registered Users 2 Posts: 3,385 ✭✭✭peckerhead


    Turn on the switch, stand in a puddle, grab the bare ends of both wires and note whether the current runs from your left to your right hand or the opposite.


  • #6
    Bruthal
    Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    peckerhead wrote: »
    Turn on the switch, stand in a puddle, grab the bare ends of both wires and note whether the current runs from your left to your right hand or the opposite.

    It changes direction 100 times a second, so good luck with that one:D


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  • #7
    fasttalkerchat
    Registered Users, Registered Users 2 Posts: 5,652 ✭✭✭fasttalkerchat


    robbie7730 wrote: »
    It changes direction 100 times a second, so good luck with that one:D

    You will have to compare exit and entry burns then :D


  • #8
    2011
    Moderators, Home & Garden Moderators, Technology & Internet Moderators, Regional East Moderators Posts: 12,663 Mod ✭✭✭✭2011


    beazee wrote: »
    Z0MGJ.jpg
    Mains tester? €2?
    These devices are not reliable, do not trust them.
    Many building sites have banned them as they have caused so many accidents.

    Proffesssional electricians use proper test equipment for this purpose.
    I use a Fluke 375


  • #9
    DannySparks
    Registered Users, Registered Users 2 Posts: 27 ✭DannySparks


    2011 wrote: »
    These devices are not reliable, do not trust them.
    Many building sites have banned them as they have caused so many accidents.

    Proffesssional electricians use proper test equipment for this purpose.
    I use a Fluke 375

    out of interest, what sites/contractors have banned them?


  • #10
    2011
    Moderators, Home & Garden Moderators, Technology & Internet Moderators, Regional East Moderators Posts: 12,663 Mod ✭✭✭✭2011


    DannySparks wrote: »
    out of interest, what sites/contractors have banned them?
    The projects I have seen them (and Stanley carpet knives BTW) banned on in Ireland include Dublin Airport, IFSC, Tallaght Hospital, several large pharmaceutical plants (that I have signed confidentiality contracts with) and Indaver.

    Abroad I worked on projects for Shell, Siemens, Elf Oil, Du Pont as well as a few others. They would not permit these "phase testers" and I agree with them. I have seen them illuminate when connected to a known earth as though it were live and not illuminate when connected to a cable I know to be at 230VAC.


  • #11
    beazee
    Registered Users, Registered Users 2 Posts: 1,343 ✭✭✭beazee


    2011 wrote: »
    I have seen them illuminate when connected to a known earth
    Where was that installation and how old it was? More likely installation needs a proper check.
    as though it were live and not illuminate when connected to a cable I know to be at 230VAC.
    Wet your finger, change your shoes


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  • #12
    2011
    Moderators, Home & Garden Moderators, Technology & Internet Moderators, Regional East Moderators Posts: 12,663 Mod ✭✭✭✭2011


    beazee wrote: »
    Where was that installation and how old it was? More likely installation needs a proper check.

    The installation did need a proper check as it was a new installation.
    I tested it with proper test equipment and this verified that it fully complied with the ETCI regulations.

    It is quite simple, proper test equipment when dealing with mains voltage or you are taking a chance.

    A quick Google search with show many examples of how unreliable and potentially dangerous these devices are.


  • #13
    golden lane
    Registered Users, Registered Users 2 Posts: 1,364 ✭✭✭golden lane


    O'Prez wrote: »
    Hi everyone. I'm putting in some new socket plates and some new ceiling lights at home. Some of the old plates I replaced were marked N and L so that was handy enough but some others aren't. The ceiling lights are another story. I'm replacing the standard bulb/lamp shade set up with chandeliers and need to know which wire coming from the ceiling is the live one. There are two...both grey. What tool would you recommend for testing which is the live one? Thanks :)

    have you got an earth wire there.........???????


  • #14
    Max_Charger
    Closed Accounts Posts: 1,323 ✭✭✭Max_Charger


    2011 wrote: »
    These devices are not reliable, do not trust them.
    Many building sites have banned them as they have caused so many accidents.

    Proffesssional electricians use proper test equipment for this purpose.
    I use a Fluke 375

    +1

    At the City and guilds course i attended,the textbook we were using told was that the best place for these,and i'm directly quoting, was "at the bottom of a lake". I always use a multimeter.


  • #15
    2011
    Moderators, Home & Garden Moderators, Technology & Internet Moderators, Regional East Moderators Posts: 12,663 Mod ✭✭✭✭2011


    Out of curiosity, what City & Guilds course?
    I did 2 of them myself, don't hear of anyone doing them anymore.


  • #16
    Max_Charger
    Closed Accounts Posts: 1,323 ✭✭✭Max_Charger


    2011 wrote: »
    Out of curiosity, what City & Guilds course?
    I did 2 of them myself, don't hear of anyone doing them anymore.

    http://www.cit.ie/course/CREEICC6

    General course with a focus on testing, found it good as testing covered by fas is brutal to say the least.


  • #17
    golden lane
    Registered Users, Registered Users 2 Posts: 1,364 ✭✭✭golden lane


    golden lane wrote: »
    have you got an earth wire there.........???????


    make sure you are switched off......connect the earth wire and one of the other wires to the old light......switch back on...if it works..then you have found the live wire.....if not it must be the other wire..switch of connect and try that one...

    switch off and put tape around the live one.....make sure that the fitting is earthed, if it has an earth connection...

    you have also proved then, that the earth wire is there to keep you safe.....


  • #18
    2011
    Moderators, Home & Garden Moderators, Technology & Internet Moderators, Regional East Moderators Posts: 12,663 Mod ✭✭✭✭2011


    golden lane wrote: »
    make sure you are switched off......connect the earth wire and one of the other wires to the old light......switch back on...if it works..then you have found the live wire.....if not it must be the other wire..switch of connect and try that one...
    If the light "works" you have just send a current down the earth. This could make the touch voltage rise on extraneous conductive parts throughout the installation to dangerous levels. Not recommended to use an earth as a neutral in this way. There is no substitute for proper test equipment and training.

    From the information provided there is no way to know the what the standard of the electrical installation is.
    you have also proved then, that the earth wire is there to keep you safe.....
    :eek::confused:


  • #19
    Bruthal
    Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    Max_Charger wrote: »
    +1

    At the City and guilds course i attended,the textbook we were using told was that the best place for these,and i'm directly quoting, was "at the bottom of a lake". I always use a multimeter.

    Multimeters can be misleading too. Intuition is needed with any testing device.


  • #20
    M cebee
    Closed Accounts Posts: 4,431 ✭✭✭M cebee


    if it's an earthed metal fitting i would do a fault loop impedance test if there's any doubt on wiring


    pendant or plastic fitting replacement
    —colours same,no cpc
    —non contact voltage indicator and flick light switch to determine phase/line


  • #21
    M cebee
    Closed Accounts Posts: 4,431 ✭✭✭M cebee


    golden lane wrote: »
    golden lane wrote: »
    have you got an earth wire there.........???????


    make sure you are switched off......connect the earth wire and one of the other wires to the old light......switch back on...if it works..then you have found the live wire.....if not it must be the other wire..switch of connect and try that one...

    switch off and put tape around the live one.....make sure that the fitting is earthed, if it has an earth connection...

    you have also proved then, that the earth wire is there to keep you safe.....

    seriously insane advice


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  • #22
    kieran24883
    Registered Users, Registered Users 2 Posts: 30 ✭kieran24883


    totally agree with, dont listen to cowboys!! get a qualified spark in, certain things you should never cut corners in and this would be one, i charge 30 quid to call out and put up a standard chandeliar(standard being very little to no assembly) cant see a this costing u much, assuming your new fitting is metal you have to have an earth wire, madness to attempt this on your own if you are in doubt


  • #23
    RoundyMooney
    Closed Accounts Posts: 10,910 ✭✭✭✭RoundyMooney


    golden lane wrote: »
    make sure you are switched off......connect the earth wire and one of the other wires to the old light......switch back on...if it works..then you have found the live wire.....if not it must be the other wire..switch of connect and try that one...

    switch off and put tape around the live one.....make sure that the fitting is earthed, if it has an earth connection...

    you have also proved then, that the earth wire is there to keep you safe.....

    Reported.


  • #24
    Stoner
    Registered Users, Registered Users 2 Posts: 10,952 ✭✭✭✭Stoner


    golden lane, your recent advice on this forum falls a little short on the health and safety side, regardless if this is intentional or deliberate please stop.


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