Rules and Guidelines
Want to participate in the discussions? Please read our Community Rules and Guidelines. Need some help? Visit Support and Answers.

  • State Helpful Answer
  • Replies 3 replies
  • Subscribers 35 subscribers
  • Views 313 views
  • Users 0 members are here
Options
You may also be interested in

Cable size between equipotential earth bonding bar and distribution board in a Group 1 medical location

Simon Bourke

The IET regulations require that the resistance of the conductors, including the resistance of the connections, between the terminals for the protective conductor of socket-outlets and of fixed equipment or any extraneous-conductive-parts and the equipotential bonding busbar (EBB) shall not exceed 0.2 Ω.

However the cable connection between the EBB and the Main Distribution board, is not defined, (identified in red in the image below) - either in terms of:

 1 - maximum resistance 

2 - minimum cable size 

3 - if the cable needs to connect to the distribution board that serves the room or should go back  to the Main distribution board.

4 - if there are number of EBB's can they be connected by a single cable in a daisy chain arrangement back to the distribution board.

Is any able to provide guidance on the four questions above?

Parents
  • 0
    Simon Bourke said:
    However the cable connection between the EBB and the Main Distribution board, is not defined, (identified in red in the image below) - either in terms of:
    Simon Bourke said:
    2 - minimum cable size

    710.415.2.3 The EBB shall be connected to the system earthing using a protective conductors having a cross-sectional area greater than or equal to the largest cross-sectional area of any conductor connected to the EBB.

    Simon Bourke said:
    4 - if there are number of EBB's can they be connected by a single cable in a daisy chain arrangement back to the distribution board.

    Connections shall be so arranged that they ... can be individually disconnected.

    To my mind, that is not consistent with a "daisy chain".

  • 0 in reply to Chris Pearson

    Thank  you for that.

    Question 1 and 2 - is answered by regulation 710.415.2.3 

    Question 4 - is answered: they should be individual connections so that they can be individually disconnected

    Can you advise regarding Question 3?

    - if the cable needs to connect to the distribution board that serves the room or should go back  to the Main distribution board.

Reply
  • 0 in reply to Chris Pearson

    Thank  you for that.

    Question 1 and 2 - is answered by regulation 710.415.2.3 

    Question 4 - is answered: they should be individual connections so that they can be individually disconnected

    Can you advise regarding Question 3?

    - if the cable needs to connect to the distribution board that serves the room or should go back  to the Main distribution board.

Children
  • +1 in reply to Simon Bourke

    Well, 710.415.2.3 is silent on the location, so I would say anywhere. Fig 710.2, which shows a typical theatre layout, simply has a bit of G/Y labelled, "CONNECTION TO PROTECTIVE EARTH IN DISTRIBUTION SYSTEM". One end is connected to the EBB and the other to a rectangle labelled, "TN DISTRIBUTION SYSTEM" from which I conclude that the local DB rather than the origin suffices.

    HTH.

Community Rules & Guidelines