Advertisement
If you have a new account but are having problems posting or verifying your account, please email us on hello@boards.ie for help. Thanks :)
Hello all! Please ensure that you are posting a new thread or question in the appropriate forum. The Feedback forum is overwhelmed with questions that are having to be moved elsewhere. If you need help to verify your account contact hello@boards.ie

Changing light fitting - possible wiring issue

Options
  • 20-05-2020 10:04pm
    #1
    tiredcity
    Registered Users Posts: 278 ✭✭


    Apologies for the very basic question but not sure an electrician will call out for this at the moment. We were changing a light fitting today and noticed the wiring seems wrong. It's a mid 80s house with the old green/black/red wires downstairs and just black/red upstairs. Upstairs there's two lights and a power shower that appear to have been installed on a series because if the 1st light isn't wired in the other light & shower don't work. There is one switch for the first light and a further switch for the light in the bathroom with the shower on a pull cable switch. Anyway the 1st light fitting is the one I'm concerned about. When we took it down there were two black wires and one red wire. The black ceiling wires were connected to the brown wire in the old fitting and the red wire in the ceiling to the blue wire in the old fitting. It was late and didn't want to start messing with it so installed the new fitting with the same setup and LED bulbs. Everything seems to be working fine but that seems literally the polar opposite of every other light I've ever changed. From googling it seems the LED bulbs wouldn't work if the wires were switched however. Anyone able to shed any light? We will be getting an electrician in for other stuff as soon as restrictions allow but just don't want to be leaving something for a few weeks if it's wildly unsafe. Thanks in advance for any advice!

    Edited to add don't have a voltage meter available so can't check that way.


Comments

  • Options
    #2
    aido79
    Moderators, Regional Abroad Moderators Posts: 5,374 Mod ✭✭✭✭aido79


    tiredcity wrote: »
    Apologies for the very basic question but not sure an electrician will call out for this at the moment. We were changing a light fitting today and noticed the wiring seems wrong. It's a mid 80s house with the old green/black/red wires downstairs and just black/red upstairs. Upstairs there's two lights and a power shower that appear to have been installed on a series because if the 1st light isn't wired in the other light & shower don't work. There is one switch for the first light and a further switch for the light in the bathroom with the shower on a pull cable switch. Anyway the 1st light fitting is the one I'm concerned about. When we took it down there were two black wires and one red wire. The black ceiling wires were connected to the brown wire in the old fitting and the red wire in the ceiling to the blue wire in the old fitting. It was late and didn't want to start messing with it so installed the new fitting with the same setup and LED bulbs. Everything seems to be working fine but that seems literally the polar opposite of every other light I've ever changed. From googling it seems the LED bulbs wouldn't work if the wires were switched however. Anyone able to shed any light? We will be getting an electrician in for other stuff as soon as restrictions allow but just don't want to be leaving something for a few weeks if it's wildly unsafe. Thanks in advance for any advice!

    Edited to add don't have a voltage meter available so can't check that way.

    Black should be joined to blue(neutral)red should be joined to brown (live). Older bulbs will work if polarity is reversed and that's why it worked alright before. Leds won't.

    You have much bigger problems than the lights if the power shower is on lighting circuit though so definitely get an electrician to check the wiring asap.


  • Options
    #3
    [Deleted User]
    Posts: 7,499 ✭✭✭ [Deleted User]


    aido79 wrote: »
    Black should be joined to blue(neutral)red should be joined to brown (live). Older bulbs will work if polarity is reversed and that's why it worked alright before. Leds won't.

    You have much bigger problems than the lights if the power shower is on lighting circuit though so definitely get an electrician to check the wiring asap.

    LEDs will work in any polarity on AC because the rectifier is in the bulb .
    And the AC becomes DC.
    AC doesnt have polarity because its alternating !


  • Options
    #4
    TheChizler
    Registered Users Posts: 9,403 ✭✭✭TheChizler


    aido79 wrote: »
    Older bulbs will work if polarity is reversed and that's why it worked alright before. Leds won't.
    On DC... Otherwise bayonette LED lamps would be tricky


  • Options
    #5
    tiredcity
    Registered Users Posts: 278 ✭✭tiredcity


    aido79 wrote: »
    Black should be joined to blue(neutral)red should be joined to brown (live). Older bulbs will work if polarity is reversed and that's why it worked alright before. Leds won't.

    You have much bigger problems than the lights if the power shower is on lighting circuit though so definitely get an electrician to check the wiring asap.

    First up thanks a million for all the replies. The LEDs are working though which is where my confusion lies. Would always have stuck black-blue red-brown previously but this is working in the configuration I said in my OP. Not fully sure I understand the AC/DC debate, apologies if I'm being stupid! Will definitely get someone out to check asap. Not 100% shower doesn't work but 2nd light & extractor fan definitely didnt when 1st light was disconnected.


  • Options
    #6
    aido79
    Moderators, Regional Abroad Moderators Posts: 5,374 Mod ✭✭✭✭aido79


    tiredcity wrote: »
    First up thanks a million for all the replies. The LEDs are working though which is where my confusion lies. Would always have stuck black-blue red-brown previously but this is working in the configuration I said in my OP. Not fully sure I understand the AC/DC debate, apologies if I'm being stupid! Will definitely get someone out to check asap. Not 100% shower doesn't work but 2nd light & extractor fan definitely didnt when 1st light was disconnected.

    Sorry I misread your post and thought you said the leds weren't working. As said by the other posters polarity doesn't matter. Ignore my brainfart saying it does.

    The lights and fan will share a neutral with the disconnected light so that's why they didn't work when it was disconnected. Check if the shower is on the same fuse/mcb as the lights. If it is you have a problem. If not it should be ok.


  • Advertisement
  • Options
    #7
    tiredcity
    Registered Users Posts: 278 ✭✭tiredcity


    aido79 wrote: »
    Sorry I misread your post and thought you said the leds weren't working. As said by the other posters polarity doesn't matter. Ignore my brainfart saying it does.

    The lights and fan will share a neutral with the disconnected light so that's why they didn't work when it was disconnected. Check if the shower is on the same fuse/mcb as the lights. If it is you have a problem. If not it should be ok.

    Great, cheers for clarifying! Makes sense finally. Will switch them around tomorrow morning and get our electrician out asap to check it over esp shower. Really appreciate the help so thanks so much all of you.


  • Options
    #8
    adrian92
    Registered Users Posts: 563 ✭✭✭adrian92


    BrownFinger wrote: »
    LEDs will work in any polarity on AC because the rectifier is in the bulb .
    And the AC becomes DC.
    AC doesnt have polarity because its alternating !

    A different question, based on your very interesting point.

    If AC doesn't have polarity, why is there phase and neutral, with different colours.

    You have raised an essential point about AC.

    Would welcome a discussion


  • Options
    #9
    Umiq88
    Registered Users Posts: 1,559 ✭✭✭Umiq88


    AC is alternating so equipment is not polarity sensitive.

    Reason for different colours is phase and neutrals are at different potentials. Neutral is at ground potential (zero volts).

    You can easily switch the neutral, reverse the polarity or put the MCB on the neutral however there is a big difference between what works and what is accepted both as legal and good practice.


  • Options
    #10
    2011
    Moderators, Home & Garden Moderators, Technology & Internet Moderators, Regional East Moderators Posts: 12,532 Mod ✭✭✭✭2011


    +1 to the above post.
    adrian92 wrote: »
    A different question, based on your very interesting point.

    If AC doesn't have polarity, why is there phase and neutral, with different colours.

    You have raised an essential point about AC.

    Would welcome a discussion

    Just because some devices are not polarity conscious does not mean that not being able to distinguish between phase and neutral is unimportant!

    Here are just 2 reasons why this is important:

    As above for safety reasons, phase conductors require a protective device (such as a fuse or MCB).

    Also if phase and neutral conductors were the same colour the risk of connecting the two together and introducing a short in a circuit is greatly increased.


  • Options
    #11
    adrian92
    Registered Users Posts: 563 ✭✭✭adrian92


    2011 wrote: »
    +1 to the above post.



    Just because some devices are not polarity conscious does not mean that not being able to distinguish between phase and neutral is unimportant!

    Here are just 2 reasons why this is important:

    As above for safety reasons, phase conductors require a protective device (such as a fuse or MCB).

    Also if phase and neutral conductors were the same colour the risk of connecting the two together and introducing a short in a circuit is greatly increased.


    I am not that knowledgeable ,but I was curious about no polarity with ac.

    Does ac have polarity, I wonder?


  • Advertisement
Advertisement