Possible earth leak?

Discussion in 'Electricians' Talk' started by fabro, May 9, 2015.

  1. fabro

    fabro Member

    I have noticed on my lighting circuit a 100-130v between the lighting earth and another earthing in the house. Using my multimeter, I get 90-100v when the light is off between the lighting earth wire and another earth (socket circuit) and 110-130v when light is switched on. There is also a 50Hz frequency between the 2 earths. I have tried in more than one place and getting the same. I inspected all the light fittings and switches and noticed the earth wires are sometimes cut short and not used so started to reconnect these but still have to do it in the loft that I have now boarded so will need to lift these.
    Can anyone give me some recommendations before I call the electrician and get all the floors and carpet lifted!!
    Thanks
     
  2. Lectrician

    Lectrician Screwfix Select

    Earth missing, as you've found. Reconnect them all, and have an earth loop test carried out.
     
  3. peter palmer

    peter palmer Screwfix Select

    Or a rewire.
     
  4. nigel willson

    nigel willson Screwfix Select

    Hi fabric, why did you just, "notice " this problem, broken earth?
     
  5. Rulland

    Rulland Screwfix Select

    Fabro probably has been doing a bit of DIY extra lighting and has run into problems, and wishes that our forum members can sort his mess, may be wrong........but....it's usually the way.
     
  6. JP.

    JP. Screwfix Select

    Do the loop test on the furthest fittings Lec?
     
  7. Mr Rusty

    Mr Rusty Screwfix Select

    Measuring just voltage with a multimeter can lead to false conclusions. I am no spark, but recently discovered I have 90v between the outer casing of USB plugs and "earth". After reading up, this turns out to be just a symptom of the filter capacitors which are wired between line and earth in the switch-mode power supplies. However, no current flows - If there was the RCD would trip. If you have any power supplies for ELV lighting in the circuit you will have caps between line and earth which maybe are responsible for this voltage showing on the MM?
     
  8. unphased

    unphased Screwfix Select

    Voltages on earths can be because an earth conductor is not connected. Do a continuity test on the cpc.
     
  9. Bazza-spark

    Bazza-spark Screwfix Select

    It also depends on the type of meter you are using. A digital mutimeter has an impedance of over 10 megomhms so requires very little current to show a voltage drop. The old type analogue instruments have a very low impedance of only a few kilohms and require a much higher current to drive the pointer.

    It isn't just measuring the voltage, it is also interpreting the results that will tell you if you have a problem or not. A dmm may indicate an induced voltage that you would not see with an analogue meter.

    Get it checked properly.

    Kind regards
     
  10. fabro

    fabro Member

    I noticed when using a cupboard light now being the en-suite light that my voltage detector was detecting a voltage when the light switch was actually off. The light fitting was removed and had put connectors instead so that I could paint the ceiling but the switch was on the off position, tried to flick the switch the other way and detected voltage too. I didn't alter the lighting circuit. I then checked with a digital multimeter and found 110v between earth and neutral or between the light earth and a socket earth. I checked elsewhere in the house and was the same. The house was rewired for sockets only. Wish the lighting had been done too.
    Can I do continuity tests to have an indication where the earth circuit is broken? I know of a few junction boxes below the floor boards and in the loft now boarded up but would be annoyed having to lift these again.

    Thanks
     
  11. seneca

    seneca Screwfix Select

    That's the reason why junction boxes are supposed to be left accessible!
     
  12. Bazza-spark

    Bazza-spark Screwfix Select

    When you boarded the loft what did you do with the cables that ran through it?
     
  13. KIAB

    KIAB Super Member

    Screwed through them...:rolleyes:
     
  14. Bazza-spark

    Bazza-spark Screwfix Select

    My thoughts entirely, or trapped them.
     
  15. fabro

    fabro Member

    I did nothing and wish I had checked all the earth connections were connected. Going through all the light switches and light ceiling roses, found that the earth were cut short and unused so reconnected them but still have 2 junctions boxes in the loft to check once I have moved the stuff and the boards. I also did a continuity test on a 2 way lighting knowing that it goes through that junction box in the corridor now underneath the carpet and the test was ok but not ok with another light switch. I might check these 2 in the loft and if the fault has not disappeared, I'll call the electrician.
     
  16. KIAB

    KIAB Super Member

    Doesn't surprise me, found the same here, even bathroom fan wasn't earthed...:(
     
  17. Bazza-spark

    Bazza-spark Screwfix Select

    Fabro, with due respect, you should have stopped when you started finding disconnected earths.

    I would suggest you put your meter away and get a professional in. He will know what he is doing and will be able to test but only lifting floorboards and carpets as a last resort, and then that will be because he is on the track of the fault. You will be lifting them without knowing what you are doing or looking for and risk doing more harm than good. He will take hours, you will take days.

    Kind regards
     
  18. fabro

    fabro Member

    Just found another light switch with 5 red wires, each have an earth cut short...I need to call the electrician now. I lucky, there won't be too much disturbance...
    thanks
     
  19. Rulland

    Rulland Screwfix Select

    There may be if he has to rewire to include earthing, who the hell does stuff like that?, the cpc, surely, is the most important core, as we all should know.
     
  20. chippie244

    chippie244 Super Member

    I knocked a 1970's stud wall in a Victorian property once and all the earths for the sockets were about 6" long.
     

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