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Regulation 643.3.3 (ii) clarification

DR Darren Hughes

I want to ask if someone can help clarify the requirements on the regulation 643.3.3, notably the second para  (or ii in GN3)

Whilst it is understood that an initial insulation resistance test should be carried out with all Sensitive loads disconnected, once they are reconnected the regulation reads "Following connection of the equipment, a test at 250 V DC shall be applied between live conductors and the protective conductor connected to the earthing arrangement."

Does this mean we are conducting two separate tests, i.e. line to CPC and Neutral to CPC? Or a single test where we link line and neutral, then test that to CPC (i.e. like previous guidance). I suspect it is the letter, but would be grateful for your thoughts.

Parents
  • +1

    Line and neutral are both live conductors, the test should really be carried out at the meter tails with line and neutral joined together to earth with the installation completed and all earthing and bonding in place.

    In the IET GN3 it says on page 69 “An insulation resistance test of line and neutral (L&N) connected together to Earth (E) will ensure all the circuit conductors are tested.”.

    But that is not what is shown in the Figure 2.21 at the bottom of the page.

    When I started work the Electricity Board meter installer working for the Midlands Electricity Board would do an insulation test at the meter tails before connecting them into the meter to test the entire installation to earth, but these days the meter operative just installs a main switch and it’s the electricians responsibility to test and make the final connection, absolving the meter installer and the electricity supplier of any responsibility it there is a big bang when the new installation is energised.

Reply
  • +1

    Line and neutral are both live conductors, the test should really be carried out at the meter tails with line and neutral joined together to earth with the installation completed and all earthing and bonding in place.

    In the IET GN3 it says on page 69 “An insulation resistance test of line and neutral (L&N) connected together to Earth (E) will ensure all the circuit conductors are tested.”.

    But that is not what is shown in the Figure 2.21 at the bottom of the page.

    When I started work the Electricity Board meter installer working for the Midlands Electricity Board would do an insulation test at the meter tails before connecting them into the meter to test the entire installation to earth, but these days the meter operative just installs a main switch and it’s the electricians responsibility to test and make the final connection, absolving the meter installer and the electricity supplier of any responsibility it there is a big bang when the new installation is energised.

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