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.
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.
Deciding to TT the charge points individually is not necessarily a good plan, and this might not comply with BS 7671 if they are in adjacent spaces ... unless you bond them all together (in which case it's all one TT, so why the number of electrodes). This is well covered in the existing 3rd Edition of the IET CoP for EV Charging Equipment Installation.
As JP has pointed out, 3rd February brings a new Amendment No. 1 to BS 7671:2018, and an updated CoP is also on the way and should be available in a few weeks' time, which will provide even further guidance on earthing systems and the problem with "deriving a TT" for charging points, as this appears to be causing a number of issues at the moment. It's not always the safest thing to do.
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.
Deciding to TT the charge points individually is not necessarily a good plan, and this might not comply with BS 7671 if they are in adjacent spaces ... unless you bond them all together (in which case it's all one TT, so why the number of electrodes). This is well covered in the existing 3rd Edition of the IET CoP for EV Charging Equipment Installation.
As JP has pointed out, 3rd February brings a new Amendment No. 1 to BS 7671:2018, and an updated CoP is also on the way and should be available in a few weeks' time, which will provide even further guidance on earthing systems and the problem with "deriving a TT" for charging points, as this appears to be causing a number of issues at the moment. It's not always the safest thing to do.
