EV install on a TT system - DNO PME?

KevinF: 
 

Thanks all - some upda I have identified what appears to be the earthing conductor as it disappears into a wall, and doing a Ze at the board with all of the other bonding disconnected from the MET I get a reading of 8.6ohms. This is not too far away from my own properties readings.

 

 

 

So hopefully all of the final circuits are protected by 30mA R.C.D.s then, especially the 16 Amp circuits and above. But wait, you say that the installation is TT earthed. So where is the earth electrode? It needs to be found. It should be visible for inspection and testing. You can't rely upon the public metal water and gas pipes as an earth electrode. 542.2.6. as Chris said earlier.

Where does the earthing conductor connect to?

Where is the main earth terminal?

What earthing arrangement is present?

We need to know.

Z.

leesrubberroom2: 
You can't have a PME'd TT system. You need to trace the main earth from the CU, and see if it goes to the incomer from the DNO, or if it goes off somewhere else. By looking at the service head, you'll see if there is an incoming earth which comes from a separate sheath (TNCS, in which case assume PME as this could be the case now or in the future) or from the neutral inside the service head. You can see some examples here in our EV's and earth rods video https://youtu.be/M51_BX1_4XI which i hope helps.

In that video link did I see an earth clamp with a red label used outside?

Z.

Well spotted Zoom, also the choice of using black for neutral and grey for earth is poor practice.  

Why is that Colin? Is that because they do not appear to be oversleeved with the correct identifying coloured sleeving? Is that S.W.A. at the black Wiska box?

Z.

The SWA cable is over sleeved with the black core sleeved blue and the grey core sleeved green/yellow. Should really be the other way around.

Is that S.W.A. at the black Wiska box?

Looks a bit like HiTuff (NYY-J) to me.

I'm not so sure about bringing the electrode connection into a Wiska box along with the live conductors where they have only basic insulation on them …. even if there's an upstream RCD it doesn't seem to meet the intent of 411.5.1.

  - Andy.

Left hand cable is SWA into a storm gland. 

Colin Haggett: 
 

The SWA cable is over sleeved with the black core sleeved blue and the grey core sleeved green/yellow. Should really be the other way around.

Yes that`s my preference too . Partly from the old Red Yellow Blue it was common to see done as Red = L , Y = earth and Blue “Oh it`s now a N colour! (The Wire Fire and F O Brigade) ” 

ebee: 
 

Colin Haggett: 
 

The SWA cable is over sleeved with the black core sleeved blue and the grey core sleeved green/yellow. Should really be the other way around.

Yes that`s my preference too . Partly from the old Red Yellow Blue it was common to see done as Red = L , Y = earth and Blue “Oh it`s now a N colour! (The Wire Fire and F O Brigade) ” 

Wasn't yellow used as a C.P.C. because it was already half of the green and yellow for earth anyway? Oversleeved with green and yellow it is quite suitable.

514.3.2. “Every core of a cable shall be  identified at its terminations and PREFERABLY throughout its length….”

So, we can use any core colour for any purpose, except green and yellow, as long as the usage is clearly indicated at terminations. I use black oversleeved with blue for neutrals if necessary. I never use green and yellow as a live conductor, sleeved or not.

Z.

I never use green and yellow as a live conductor, sleeved or not.

Probably no riskier than over-sleeving a ‘live’ colour with G/Y and using as a c.p.c. …. just that the danger comes from mistakes at the opposite end of the cable.

    - Andy.