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Distance between other electrical systems

Former Community Member
Former Community Member
Hi all,


I've been asked this time and time again and it could be a case that I've looked at this so much that it's made me go insane, but I'd like a 2nd opinion.


When installing a TT feeder pillar on the street, does the 2.5m rule come into effect when it's located near to a PME system or does this need to be 2.5m away from all other systems which are not connected to the same earthing system (not connected to the earth mat/rod under the feeder pillar?  


My personal opinion is that they should be 2.5m away from anything that isn't on the same electrical installation (even if it's another TT system nearby) as if there's a fault with one and the path to earth is broken then the path would flow directly between the person or whatever touches it and take the route of least resistance. I have my copies of the 18th edition and the CoP for EVCEI, but I've been looking at it for so long it's made things become less clear the more questions I'm being asked about the regs!


Any help would be much appreciated,


Regards,


S
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  • Former Community Member
    0 Former Community Member


    Hi Graham,


    I've done a quick drawing on a typical site to help explain what I'm proposing, and what would essentially happen is that you could install a link between all three METs, this would also increase the surface area of the copper earthing rods/mats and overall reducing the Ze. This would require the permissions of those who own/maintain the adjacent equipment to allow the earthing systems to be combined and also the installation of a label/notice, similar to the standard "Safety electrical connection, DO NOT REMOVE", maybe "This earthing system is interconnected with adjacent equipment - Do not remove", the furniture this is connected to could be confirmed by performing an R2 test with a wandering lead.


    This would reduce the danger of having a potential between items and create a lower path of resistance to earth that the safety mechanisms of ADS and additional protection would be able to activate in an even shorter amount of time.
    c4ea1b79f30e0cb1071ad19d42b8149d-huge-20190514_094214.jpg

    It seems like a very particular situation but in many streets and side roads, there is frequently only one supply cable which would make this possible, if the other installations weren't TT, then it may be possible to convert them to TT with the owners permission or to have them converted by the owner themselves. Wouldn't this remove the need for the required  2.5m between items? I admit, there are many "if"s involved, but we need to have a sensible method of being able to install the EVCE before it becomes impossible due to adjacent street furniture. 


    If I've overlooked something, please let me know and I can have a look at different ways around the issue.

Reply
  • Former Community Member
    0 Former Community Member


    Hi Graham,


    I've done a quick drawing on a typical site to help explain what I'm proposing, and what would essentially happen is that you could install a link between all three METs, this would also increase the surface area of the copper earthing rods/mats and overall reducing the Ze. This would require the permissions of those who own/maintain the adjacent equipment to allow the earthing systems to be combined and also the installation of a label/notice, similar to the standard "Safety electrical connection, DO NOT REMOVE", maybe "This earthing system is interconnected with adjacent equipment - Do not remove", the furniture this is connected to could be confirmed by performing an R2 test with a wandering lead.


    This would reduce the danger of having a potential between items and create a lower path of resistance to earth that the safety mechanisms of ADS and additional protection would be able to activate in an even shorter amount of time.
    c4ea1b79f30e0cb1071ad19d42b8149d-huge-20190514_094214.jpg

    It seems like a very particular situation but in many streets and side roads, there is frequently only one supply cable which would make this possible, if the other installations weren't TT, then it may be possible to convert them to TT with the owners permission or to have them converted by the owner themselves. Wouldn't this remove the need for the required  2.5m between items? I admit, there are many "if"s involved, but we need to have a sensible method of being able to install the EVCE before it becomes impossible due to adjacent street furniture. 


    If I've overlooked something, please let me know and I can have a look at different ways around the issue.

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