Details of BS7671:2018 Amendment 1 are here.

well, given that you cannot bond exposed blades of grass, or the surface of the flower beds, which are equally touchable and tingly to bare feet, some things are best left to float to local terra-firma potential, and anything planted in it that is short, like a fence post is probably best left alone.

Agreed - although to  square that with BS 7671's requirements we'd probably need something equivalent to 714.411.3.1.2 in section 722.


Actually that thinking meshes rather well with an approach I suggested for the DPC - which was along the lines of making the earthed metalwork of the EV and charge point practically no more hazardous than a simple piece of metal stuck into the ground. Basically a more stringent version of TT but with 0.2s (or better) disconnection times throughout (no option for 1s), R_A x I_Δn≤25V (rather than 50V) and the electrode in the immediate vicinity of the charge point - all reasonably easy to achieve with a normal 30mA RCD and 200 Ohm rod setup. In that way almost everything is close enough to local earth potential not to be a hazard under any normal or single fault condition so I'd argue no bonding required at all. In highway locations PME'd lampposts etc. shouldn't really be a problem under broken PEN conditions if they have the additional electrodes that DNOs have been specifying for years (one of the few cases where the load is low enough for that approach to be practical) - so we're only left with situations where exposed- or extraneous-conductive-parts connected to larger installations are available to the touch - but that problem was there already and not really anything to do with the EV setup - and experience shows (see reg 714.411.3.1.2 for example) that the risks are very small in practice anyway. Seemingly that wasn't a convincing argument - so if anyone can see the flaws I'd be very interested!

  - Andy.

well, given that you cannot bond exposed blades of grass, or the surface of the flower beds, which are equally touchable and tingly to bare feet, some things are best left to float to local terra-firma potential, and anything planted in it that is short, like a fence post is probably best left alone.

Agreed - although to  square that with BS 7671's requirements we'd probably need something equivalent to 714.411.3.1.2 in section 722.


Actually that thinking meshes rather well with an approach I suggested for the DPC - which was along the lines of making the earthed metalwork of the EV and charge point practically no more hazardous than a simple piece of metal stuck into the ground. Basically a more stringent version of TT but with 0.2s (or better) disconnection times throughout (no option for 1s), R_A x I_Δn≤25V (rather than 50V) and the electrode in the immediate vicinity of the charge point - all reasonably easy to achieve with a normal 30mA RCD and 200 Ohm rod setup. In that way almost everything is close enough to local earth potential not to be a hazard under any normal or single fault condition so I'd argue no bonding required at all. In highway locations PME'd lampposts etc. shouldn't really be a problem under broken PEN conditions if they have the additional electrodes that DNOs have been specifying for years (one of the few cases where the load is low enough for that approach to be practical) - so we're only left with situations where exposed- or extraneous-conductive-parts connected to larger installations are available to the touch - but that problem was there already and not really anything to do with the EV setup - and experience shows (see reg 714.411.3.1.2 for example) that the risks are very small in practice anyway. Seemingly that wasn't a convincing argument - so if anyone can see the flaws I'd be very interested!

  - Andy.