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 17 replies
  • Subscribers 40 subscribers
  • Views 1040 views
  • Users 0 members are here
Options
You may also be interested in

Adding a bonding conductor to an existing main earth terminal

Electron666

Hi do you need to isolate the supply to a commercial building to connect a 16mm2 bonding conductor to the MET in relation to BS 7671 or HSE?

It isn't something I can find explicit guidance on.

The MET is at the intake and separate to the main LV board.

It is easily accessible without coming into contact with L&N conductors connected to the main LV board.

The earthing system is either TN-S or TN-C-S.

Isolating the supply is possible if required but would be costly, require multiple companies attending out of hours and would need to be planned in well in advance due to it being a refrigerated / food storage facility.

I note all these reasons are inconvenience related which is secondary to health and safety. Therefore, I'm only asking if there is a method that is commonly used such as standing on rubber mats or wearing rated gloves etc that is considered safe and proportionate to the to the small task being carried out.

Thanks

Parents
  • 0
    Chris Pearson said:
    the earthing conductor and MET will remain connected to the DNO's earth.

    How, the OP stated that the supply wasn't TN-S or TN-C-S.

    However, we can't discount the fact that if it's another earthing arrangement (say TT or IT), then if the area has PME, diverted neutral currents can persist through other extraneous-conductive-parts where these are shared with PME installations, or come close to buried metalwork connected to the PME system !

    Electron666 said:
    The earthing system is either TN-S or TN-C-S.

    It would help us if you said what it is, rather than what it isn't? Is it an IT earthing arrangement, for example?

    Without this knowledge, it's not really possible to answer your question.

  • +1 in reply to gkenyon
    gkenyon said:
    How, the OP stated that the supply wasn't TN-S or TN-C-S.

    Graham, you may have mis-read that. I understood Electron666 to mean that it is one or the other.

  • 0 in reply to gkenyon

    Hi, thanks for your responses.
    A 16mm2 bonding conductor is required to be connected to a spare way on the MET on a number of separate sites.
    Some sites have a TN-S earthing arrangement and some are TN-C-S.
    As mentioned the earth bar is separate to the main LV board and easily accessible without having to temporarily disconnect any other existing earth or bonding connections and operatives can keep safely away from any L&N conductors.

    The question was asked if there need to be full shut down in line with BS 7671 and HSE requirements to make this bonding connection. A shut down is possible but timely, costly and inconvenient due to chilled food refrigerated circuits. If there was a safe way to make the connection without this then great. If not then H&S first and a full shut down needs to happen.
    Hopefully this provides more clarification.

  • 0 in reply to Electron666

    Unfortunately you're unlikely t get a simple yes/no answer - as UK safety legislation is less 'thou shalt or thou shalt not' but is more along the lines of obliging you to recognise risks and mitigating them, While isolating is one traditional way of "making things safe" it's not the only possible approach (and in this particular case perhaps not even an adequate one on its own). It's all horses for courses and allowing flexibility to deal with a vast range of differing situations in sensible ways.

       - Andy.

  • 0 in reply to Electron666
    Electron666 said:
    to be connected to a spare way on the MET

    So, IIUC, the real problem (if there is one) is that:

    the remote 'earth/CPC' that is to be bonded, from the remote system, to this existing spare way, may introduce a potential fault current, in some way, by the provision of an additional parallel path? 

    The problem is NOT the need to disconnect one of the existing 'earths' at the MET to gain access to, or create, a spare way for the connection.

Reply
  • 0 in reply to Electron666
    Electron666 said:
    to be connected to a spare way on the MET

    So, IIUC, the real problem (if there is one) is that:

    the remote 'earth/CPC' that is to be bonded, from the remote system, to this existing spare way, may introduce a potential fault current, in some way, by the provision of an additional parallel path? 

    The problem is NOT the need to disconnect one of the existing 'earths' at the MET to gain access to, or create, a spare way for the connection.

Children
No Data

Community Rules & Guidelines