A 4 storey office block with it's own transformer on a TNCS system requires 20 EVC points located in a rear goods yard. Each are 11kw 3 phase so 16A TP apiece via 16A Type A RCBOs. Each EVC will be independanly spiked using either a traditional earth spike or a Condudisc to make them TT. All SWAs will terminate at an adaptable box in LV Switchroom mounted below D/Board thus keeping all EVC earths seperate to that of the TNCS. The plan is to install a metal construction solar panel canopy over the 20 parking bays. Presumably this will need earthing but to which system? The legs of the canopy are metal and may fall within 2m of a number of EVCs. I'm guessing bond them to the local TT Charging point? The other issue is the solar on the canopy roof which is importing back into the buildings LV TNCS System currently serving the building and the question is - will this need earth seperation and to what system. Any feedback is greatly appreciated.
Even if you TT the whole installation or just TT the EV charging socket the problem is getting the TT electrode away far enough from any under ground metallic pipes or metal work that is connected to the PME earthing system or connected to your neighbors PME earthing system.
Hence one of the comments directed at the DPC - what we should be seeking is equipotentiallity with the ground under/around the EV, rather than equipotentiallity with some theoretical zero volts (the potential of the centre of the planet?). Hence if the ground in the vicinity of the EVSE/EV is subject to potentials from a PME system it makes sense for the TT electrode to match the very same potentials if we're to minimise shocks between the EV and the surface of the ground (or random metalwork - posts for signs etc - stuck in the same ground). Make the electrdode(s) local to the EVSE (a buried grid under the parking space if you're really worried about voltage gradients across such a small area) and it all just comes out in the wash.
Even if you TT the whole installation or just TT the EV charging socket the problem is getting the TT electrode away far enough from any under ground metallic pipes or metal work that is connected to the PME earthing system or connected to your neighbors PME earthing system.
Hence one of the comments directed at the DPC - what we should be seeking is equipotentiallity with the ground under/around the EV, rather than equipotentiallity with some theoretical zero volts (the potential of the centre of the planet?). Hence if the ground in the vicinity of the EVSE/EV is subject to potentials from a PME system it makes sense for the TT electrode to match the very same potentials if we're to minimise shocks between the EV and the surface of the ground (or random metalwork - posts for signs etc - stuck in the same ground). Make the electrdode(s) local to the EVSE (a buried grid under the parking space if you're really worried about voltage gradients across such a small area) and it all just comes out in the wash.
