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Thread: Earth leakage problem

  1. #11
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    By the way we are assuming that you are a qualified electrician ...you use your test equipment on a daily basis ...your test equipment is calibrated as required and you have had suitable training on the use of the equipment?

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    Your assumption is very true. I am a qualified installation electrician but I have not been in the field for a long time as some of you have been. So my experiences are very limited and I believe from you guys there is a lot I can learn.

    Any way I have checked the EL tester from another installation and is working perfectly.
    Now, there something else I have discovered on that faulty earth leakage installation. When I perform the loop impedance and pscc test on the DB before the earth leakage, the readings i obtain are 265 ohms and 0.9 A (not kA) respectively. This is not making any sense to me. Any I deas?

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    Couple of questions.

    1. Is the DB supplied directly from Supply Authority or is it a sub DB ?

    2. If supplied from Supply Authority, is it overhead or underground supply ?

    3. Is there an earth supplied by Supply Authority or not ? ie. 2 wire or three wire supply.
    This might sound like a strange question, but I know of whole suburbs and settlements where earths are not supplied by Supply Authority.

    4. Hit in an earth spike. Connect to earth bar in DB using 10mm wire and redo test.

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    This is the main DB fed from a 60A breaker installed inside a box mounted on the wall outside.
    The supply system is underground and has an earth provided.
    I am not sure if the earth in this box mounted on the wall outside is from the supply authority or not.

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    Somehow I think you should get an electrician to come and find the fault .....

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    Much appreciated, thank you.

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    Quote Originally Posted by Philani View Post
    Now, there something else I have discovered on that faulty earth leakage installation. When I perform the loop impedance and pscc test on the DB before the earth leakage, the readings i obtain are 265 ohms and 0.9 A (not kA) respectively. This is not making any sense to me. Any I deas?
    Test at the meter. If it's fine at the meter, the problem is with the supply cable between the meter and the main switch.
    The trouble with opportunity is it normally comes dressed up as work.

    Alcocks Electrical Services | Alcocks Pest Control & Entomological Services

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    Are the socket outlets wired with a separate earth wire or are you depending on the conduit for an earth? I have found rusted conduit that will show an earth on the tester indicator light, but is inadequate to trip the earth leakage. Less than 30 mA flowing to earth. The tester lights may flicker and on some earth leakage units you will hear it hum, but it will not trip. A separate earth continuity test will prove whether you have a reliable earth. Most of the cheaper earth leakage testers will trip the e/l unit with next to no earth present but if there is really very little earth, it will fail to trip. In older houses you will also find that socket outlets are changed with newer ones with plastic casings. If the conduit was used as earth, the new plug must be equipped with a flying lead from the earth terminal that is securely earthed to the wall box. Is this problem on all the socket outlets or on one only? I have found homes where the distribution board was changed for a newer surface mounted unit and the earth bar with all the earth connections left in the old board in the wall, behind the new board and not connected to the earth bar in the new board. The new board is then in effect not earthed at all except for the wall plugs securing it to the brick wall. Lots of funny things pop up with tests.

  9. #19
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    Quote Originally Posted by Henthel View Post
    Are the socket outlets wired with a separate earth wire or are you depending on the conduit for an earth? I have found rusted conduit that will show an earth on the tester indicator light, but is inadequate to trip the earth leakage. Less than 30 mA flowing to earth. The tester lights may flicker and on some earth leakage units you will hear it hum, but it will not trip. A separate earth continuity test will prove whether you have a reliable earth. Most of the cheaper earth leakage testers will trip the e/l unit with next to no earth present but if there is really very little earth, it will fail to trip. In older houses you will also find that socket outlets are changed with newer ones with plastic casings. If the conduit was used as earth, the new plug must be equipped with a flying lead from the earth terminal that is securely earthed to the wall box. Is this problem on all the socket outlets or on one only? I have found homes where the distribution board was changed for a newer surface mounted unit and the earth bar with all the earth connections left in the old board in the wall, behind the new board and not connected to the earth bar in the new board. The new board is then in effect not earthed at all except for the wall plugs securing it to the brick wall. Lots of funny things pop up with tests.
    It use to be common practice to fit surface DB's over old flush units.

    Some bright sparks fit surface mount 4X4 pvc boxes over old 5 amp sockets or 4x2 flush mount sockets and just connect the 2 wires to the new plastic box and plug... when i contacted electrical contractor who fitted these boxes ever room in the entire duplex ... he said there is no way the labour he left on site would do such a silly thing.

    This is why i believe it is important to carry out a random loop impedance test at socket outlets.
    Comments are based on opinion...not always facts....that's why people use an alias.

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