TNS - to TT conversion

[chris day]

EDF have requested a building be converted to a TT system.

Currently a TNS 2x100a head supplies a shop then a flat respectively.

The are x2 fuse boards supplying the two areas each having 30ma RCD protection on all final circuits.

Am I correct in saying in simple terms X1 earth spike Into ground, separate the TNS - TT earthing systems from each other and x2 200ma time delay main RCD switches on the two supplies on the meter tails for each supply.

 

[R-fur]

Why have EDF requested this? If they supply an earth then they have a duty to maintain it. If they no longer want to supply an earth then they should be paying to have the installation TT'd

 

[chris day]

Apparently not, client had been told specifically to be responsible for their own Earth.

 

[davesparks]

Why are EDF requesting this? They are not a licensed DNO in the UK so it's none of their business.
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Am I correct in saying in simple terms X1 earth spike Into ground, separate the TNS - TT earthing systems from each other and x2 200ma time delay main RCD switches on the two supplies on the meter tails for each supply.

No, you need as many earth rods as is necessary to create a stable and reliable earth connection. The chances of 'X1 spike' satisfying this requirement are slim to none.

As you have two seperate installations you need to consider how the earthing systems of the two installations will interact.
Assuming you need to link the earthing systems of the two installations you need to ensure that an alteration to one installation won't have a detrimental effect on the other one. e.g. If someone carries out an EICR on one installation and disconnects the earthing conductor to carry out testing will this leave the shop installation live without an earth?

If you install one set of earth electrodes to serve both installations who will own and be responsible for maintaining the earth electrode network if it is shared by two installations?

If you install seperate sets of earth electrodes for both installations will you need to, or be able to, physically seperate them?

 

[westward10]

As above I don't get this. Are they asking to TT both installations or just the new converted part.

 

[PEG]

We can begin from the beginning...what readings were obtained,from the origin?
What has anyone been instructed,to do with the existing earth arrangements?

 

[snowhead]

Has this got anything to do with "Smart" Meters or the installation of?

 

[chris day]

there Is only one supply for both parts of the building so only need one TT rod, the head splits bits is one supply still

 

[davesparks]

there Is only one supply for both parts of the building so only need one TT rod, the head splits bits is one supply still

The number of supplies does not dictate the number of rods, the type and condition of the soil dictates the number of rods.

What do you mean by the head splits? If there two meters and two installations connected to the same head then that is still two installations.