Neutral goes live! 3red1black

Discussion in 'Electricians' Talk' started by Davidd84, Apr 2, 2016.

  1. Davidd84

    Davidd84 New Member

    Good evening people,

    So I have this issue with the ceiling pendant in the bedroom closest to the fuse box. when you strip it down there are 3 red and 1 black cable, only one of these red cables are live when tested so I placed that in middle of the LOOP on the pendent one to the L and one to the LOOP again to complete the loop and the black to the North sounding correct so far?
    However when I attach the flex with the rose to the L and the N both start receiving power on the tester, I've tried different variations of placing the red cables.

    Any help much appreciated
     
  2. MGW

    MGW Screwfix Select

    As you say in theroy with one twin and earth having two red wires going to the switch you should not be able to go wrong. Line to centre with one other red, remaining red to double outer and black to triple outer connect block.

    So if you are measuring line on the black first thing that springs to mind is what are you using as a reference point? I know we some times use the earth but that will only work if we really have an earth. Before 1966 there were often no earths. So first stage is to ask what are you using as a reference point?
     
  3. Davidd84

    Davidd84 New Member

    You are correct there are no earth cables in this flat to my surprise. So I've attached my tester and one red is the switch cable (as the circuit is made when you flick the switch) and one the permanent live so my assumption is the other red is part of the loop to the sitting room or hallway, after doing some research I'm thinking the black maybe a black that should be sleeved red and the red I through was loop should be sleeved for N (black)

    That could be the reason for the the L and N going live when I connect the pendant flex... All the others in the house have there own mix of colours to L and N so very confusing but all of the N on the other pendants do not read live on the tester
     
  4. fire

    fire Well-Known Member

    The neutral will always become live and carry current once a circuit is made, as in a load such as a light bulb is placed across the live and neutral then the current will flow through the bulb making the neutral to carry current.

    It should also be noted that current could flow in the neutral if something else is connected to the circuit, such as a light further down on the lighting circuit.

    Out of interest, are the wires running in metal conduit?

    No Earth wire is not acceptable by today's regulations so consider a re-wire. Maybe just re-wire your lighting circuits with twin and earth.
     
  5. Davidd84

    Davidd84 New Member

    Okay so do you kn why the light will not come on once it's connected up? When I look it feels like it's run correctly and if the N starts receiving power once flex and bulb are fitted should it not be fully functional?
    It was just strange that the other lights don't have a current flow when I tested the N and they was on at the time but the bedroom does! could someone have don't something in the sitting room fitting that has affected the loop?

    In answer to your other questions yes they are in metal Junction box's it's an ex council property with concrete ceilings, had a electrician out last week to replace the bathroom light and he said nothing wasn't untill I looked at the bedroom/hall/sitting room and I've seen no earth cable >:/

    It's not my flat it's just been brought by my girl and she said there was a strange arrangements of two pendents on the ceiling when she viewed the flat now that's been removed it's not working, so I'm thinking the previous owner has bypassed something
     
  6. fire

    fire Well-Known Member


    Metal conduit is the Earth, very common for metal conduit installations. Many prefer to run a separate earth wire in metal conduit but the metal conduit being a conductor is adequate or at least was back in the day of installation.

    It sounds like you have a voltage drop, so much so that there is not enough current flow to power the bulb. I would re-check all connections and make sure they are tight. You may have a damaged cable, bad insulation. Did the electrician do a full test particularly the insulation test which is where you remove all bulbs and shoot 500v down the wiring to see what the resistance is?

    Two pendants...

    Interesting, would that not mean there is another hole in the ceiling somewhere that had wires going to it. You could be getting false reading as the neutral is having a current flow from somewhere else.

    What tester are you using?
    What test equipment have you at your disposal?
    Is it a multimeter or a neon screwdriver that you touch your thumb on the back of to check for live conductors?

    Also test the switch, it has been know that the light switch fails to make proper connection when switched on as the springs break or weaken and don't make good contact on their terminals.
     
  7. Davidd84

    Davidd84 New Member

    That's great news about the earth then one less thing to worry about!

    I have been using a continuity tester from Screwfix and also the neon screwdriver.
    No I don't believe he did a full test but because I wasn't involved with him I cannot be certain (I'll enquiry nxt week as what he did)

    In the bedroom there is the original fitting and the previous owner had another cable and pendent run on the outside of the ceiling not another junction box( we thought it was just so the light was in the centre of the room) I'll ask her for a photo if she has it still of when she did her first viewing.
     
  8. fire

    fire Well-Known Member


    Them Neon screwdrivers can give false readings, be careful.

    You can light one of them up with a standard walkie talky they really are not a safe tester. Use a multimeter instead, they are not expensive and have multiple uses, well worth investing in one.

    The best are the true RMS multimeter's but they go up in price the better they get.
     
  9. Davidd84

    Davidd84 New Member

    Yeah I only use it as it's a screwdriver as well... I use this as my primary tester LAP MAS830B Digital Multimeter 600v
    http://m.screwfix.com/p/lap-mas830b-digital-multimeter-600v/75337?kpid=75337&cm_mmc=Google-_-Product%20Listing%20Ads-_-Sales%20Tracking-_-sales%20tracking%20url&cm_mmc=Google-_-Shopping%20-%20Electrical%20and%20Lighting-_-Shopping%20-%20Electrical%20and%20Lighting&gclid=CjwKEAjw_oK4BRDym-SDq-aczicSJAC7UVRttIDh2zeLoy6-5QXjJiUzdMSWCwwmFBr2tLTtZe7ybxoCkw7w_wcB

    Tomorrow I'll change the switch and run around tighting all connection. Will it make a difference if I use a 1g 1way or 1g 2way switch? as I already have a 2way
     
  10. Davidd84

    Davidd84 New Member

    This was how it looked before she brought the flat
     

    Attached Files:

  11. Brian_L

    Brian_L Active Member

    Didn't she like the town the flat was in then?
     
  12. fire

    fire Well-Known Member

    WT* was that a dual purpose washing line/light fitting?

    To note some of these flats had a bedroom pull cord switch for multi-way lighting. It was done for the elderly to make it easy for them to turn the light out from their bed once in bed.

    1 way or 2 way would make no difference, if you only have two wires in your light switch back box you can only use the common and L1 or L2 depends which way round you want the switch in the on position.
     
  13. Davidd84

    Davidd84 New Member

    Have no idea why there was 2 I through it was to have the light in the middle of the room as the original location was by the window. I'm gonna do a full test of the lot tomorrow and see, I'll also take some more photos of the bedroom, Hall and sitting room so you can see what I'm seeing.

    That's for all the responses guys
     
  14. madhatter1uk

    madhatter1uk Screwfix Select

    That is to move the light position. There shouldn't be anything there where it was now?
    It depends on where the rose is in the circuit and how many switches there are at the position. Is the red still live with the switches in the other position. Are any of the others live with switches flicked over.
     
  15. Davidd84

    Davidd84 New Member

    My girl that owns the flat her father come and took down the extentions so now we back at the original position.

    There are 3 red and of them 3 only 1 is live permanently when I connected it all up and flick the switch the other red goes live so can tell the switch is functional. But still gonna change the switch tomorrow as it's old
     
  16. madhatter1uk

    madhatter1uk Screwfix Select

    Does this other one go live when the switch is on if you disconnect the permanent live?
     
  17. Davidd84

    Davidd84 New Member

    I'm not at her flat now but I don't think it did
     
  18. madhatter1uk

    madhatter1uk Screwfix Select

    You also need to check how many pipes enter the box and if any wires pass straight through.
    Try connecting the permanent live straight to the light and see if it lights without the other wires in the circuit. Then you know the fitting is working.
     
  19. Davidd84

    Davidd84 New Member

    I tried that and it didn't work so I took the fitting to the hallway put it on the L and N and it worked, so that's why I'm now thinking the black may not be a N after all as in the sitting room there is a couple black in the L.

    I feel like someone has messed with the sitting room and that's why the bedroom don't work.

    From what I remember it has one pipe coming in and nothing running through. Looks like the last box on the circuit.
     
  20. madhatter1uk

    madhatter1uk Screwfix Select

    You need to try to find out where those are coming from. If there's a couple of blacks in a live then the other end must be live too
     

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