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ISO Containers Earthing & Bonding - TNCS (PNB) Supply

Former Community Member
Former Community Member
I have a project to provide a 63A TP supply terminating with a Type B DB within an ISO container. Final circuits from the DB will supply industrial sockets located in the ISO via RCBO's and an external fan.

The ISO container is located on several concrete pads and internally is fully (wooden) boarded out.

The supply is TNCS PNB.

My current proposals are for a connection via a SWA supply cable (4c) and separate CPC, fed via a 63A Type C MCB.

The CPC will terminate onto a EMT.

The ISO container will have a main protective bonding conductor to the EMT using finely stranded cable. In addition bonding via flexible 'straps' will be provided to the doors.

I have not allowed to TT the installation due to the PNB supply.


Looking for advice on whether a local earth rod or ring earth electrode is the best option to earth the container locally and also the resistance figure to achieve.


Thanks Mike

 


 

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    Mikey70:

    Thanks for the responses. Graham, yes it is via an DNO supply, although it is buried supply cables with a TX on a pole located adjacent the Switch Room.

    If with this type of PNB supply PME conditions apply then yes TT connection using a time delay RCD (instead of the MCB), earth rod at the container, RCBO's to the outgoing circuits.

    If not PME then would the original proposal be meet the guidance ie PNB supply via private TX ?

    Thanks.

     


    If the supply is an installation with a couple of sources such as a generator and privately-operated transformer, where the N-E bond is made at the switchboard (instead of separately at the generator and transformer) to prevent circulating currents, then that is technically PNB, but:

    (a) PME conditions do not apply; and

    (b) You can generally consider the installation downstream of the main switchboard as TN-S.


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  • 0
    Mikey70:

    Thanks for the responses. Graham, yes it is via an DNO supply, although it is buried supply cables with a TX on a pole located adjacent the Switch Room.

    If with this type of PNB supply PME conditions apply then yes TT connection using a time delay RCD (instead of the MCB), earth rod at the container, RCBO's to the outgoing circuits.

    If not PME then would the original proposal be meet the guidance ie PNB supply via private TX ?

    Thanks.

     


    If the supply is an installation with a couple of sources such as a generator and privately-operated transformer, where the N-E bond is made at the switchboard (instead of separately at the generator and transformer) to prevent circulating currents, then that is technically PNB, but:

    (a) PME conditions do not apply; and

    (b) You can generally consider the installation downstream of the main switchboard as TN-S.


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