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Thread: Off grid solar system

  1. #1
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    Off grid solar system

    A customer asked me to check the earthling of his installation after a short on an appliance did not trip anything in the DB. Tests at the socket outlets showed an earth fault. Measuring at the inverter outlet terminals I got a reading of 37 volts between neutral and earth. Is the fault with the inverter
    or is it possible that the earthing is not correct, ( he has used a steel fencing post as a earth spike .) Also is it safe for me to do an earth loop test at the DB, not sure if it will have any adverse effects on inverter? Any advice will be appreciated.

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    The neutral and earth is not bonded on the output of the inverter - Check the inverter specs but you will need to join them

    Regulation from SANS10142-1 ED3 pasted below

    7.12.3.1.3 Where alternative supplies are installed remotely from the
    installation, or from one another, and where it is not possible to make use of
    a single neutral bar or neutral conductor which is earthed, the neutral of each
    unit shall be earthed at the unit and these points shall be bonded to the
    consumer's earth terminal (see 6.12.4). The supply from each unit which
    supplies the installation or part of the installation, shall be switched by means
    of a switch that breaks all live conductors operating substantially together (see
    figures P.2 and P.4), to disconnect the earthed neutral point from the
    installation neutral when the alternative supply is not connected (see also
    6.1.6).

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    Thanks for the advice GEC, confirms what I suspected . Is it safe for me to do a earth loop test at the DB, not sure if this will have any adverse effects on the inverter?
    Also another question regarding a generator installation with a built in ATS , do I earth the neutral on the load side of the change over switch or on the generator supply side?
    Thanks again.

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    Earth the neutral on the generator side

    You may not earth the suppliers neutral so you need to ensure that you have a 4 pole ATS switching if you are not taking full load of the transformer , or if you don't own the transformer.

    Pasted the relevant reg below


    6.1.6 The neutral conductor shall not be connected direct to earth or to the
    earth continuity conductor on the load side of the point of control except as
    allowed in 7.16.4

    3.56
    point of control
    point at which a consumer can, on or in any premises, switch off the electrical
    installation from the electricity supplied from the point of supply
    3.58
    point of supply
    point at which a supplier supplies electricity to any premises

    7.16.4.6 A TN-S system shall not be converted to a TN-C system.

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