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.
Sorry to be a party pooper but your plan needs a major re-think.
Firstly if this building has it's own transformer it will highly likely be a TN-S supply. The other alternative it might be TN-C-S (PNB) but not likely to be the other flavour of TN-C-S (PME) unless the transformer supplies other buildings? The special provisions only apply to TN-C-S (PME) and as your supply probably lacks the "M" it is not going to be PME. A more detailed survey is required to determine the actual means of earthing.
TTing the charging points with your earth electrodes with circa 2m of the legs of the metal canopy legs is likely to overlap the earth resistance fields of the 2 effectively connected your 2 earthing systems together. You cannot have simultaneous access between 2 earthing systems, see the Part 2 definition and Regulation 411.3.1.1.
I would say that a 11kW 3 phase load is a bit tight for a 16A MCB. This Type A RCBO you speak of is it 4 pole? If I was you, and I have carried out a design recently for 2 No pillar unit each with 2 No. 11kW 3 phase units, I would use units with a 3 phase Type A inside with DC sensing so all you need to do is run out the required 3 phase supplies from an MCB for each socket. I use a company starting with "R" and ending in "C", other makes are available.
Also 20 11kW units is potentially a very large load on the installation. Will the installation take the additional load and have you sort permission from the DNO before you think about starting the installation work? You may need to fit load control to you charging points given the no diversity rule.
You cannot start the installation without verify the earthing system, any bonding required and ensuring the installation will take the additional load, see Regulation 132.16. Also the installation needs to be designed which is a process that most contractors seem un-aware of but are happy to sign the declaration on the EIC to the effect the installation has been designed to BS 7671.
You might want to wait until this Monday when the IET will make available the 18th Edition AMD 1, free to view on line £5 to download and have a good read before starting your design.
Sorry to be a party pooper but your plan needs a major re-think.
Firstly if this building has it's own transformer it will highly likely be a TN-S supply. The other alternative it might be TN-C-S (PNB) but not likely to be the other flavour of TN-C-S (PME) unless the transformer supplies other buildings? The special provisions only apply to TN-C-S (PME) and as your supply probably lacks the "M" it is not going to be PME. A more detailed survey is required to determine the actual means of earthing.
TTing the charging points with your earth electrodes with circa 2m of the legs of the metal canopy legs is likely to overlap the earth resistance fields of the 2 effectively connected your 2 earthing systems together. You cannot have simultaneous access between 2 earthing systems, see the Part 2 definition and Regulation 411.3.1.1.
I would say that a 11kW 3 phase load is a bit tight for a 16A MCB. This Type A RCBO you speak of is it 4 pole? If I was you, and I have carried out a design recently for 2 No pillar unit each with 2 No. 11kW 3 phase units, I would use units with a 3 phase Type A inside with DC sensing so all you need to do is run out the required 3 phase supplies from an MCB for each socket. I use a company starting with "R" and ending in "C", other makes are available.
Also 20 11kW units is potentially a very large load on the installation. Will the installation take the additional load and have you sort permission from the DNO before you think about starting the installation work? You may need to fit load control to you charging points given the no diversity rule.
You cannot start the installation without verify the earthing system, any bonding required and ensuring the installation will take the additional load, see Regulation 132.16. Also the installation needs to be designed which is a process that most contractors seem un-aware of but are happy to sign the declaration on the EIC to the effect the installation has been designed to BS 7671.
You might want to wait until this Monday when the IET will make available the 18th Edition AMD 1, free to view on line £5 to download and have a good read before starting your design.
