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Silly Sausage
What should a certain member do?
Discuss Earthing for an EV Charging Point in the Electric Vehicles Advice Forum area at ElectriciansForums.net
What should a certain member do?
UK, have you not understood anything we have being saying to you ?
You have a few options,
1) ensure the three Phase supply is balanced according to the formula in the associated annexe with exemption I), and then it doesn't really matter how good the building is earthed to true earth, the load balancing alone will prevent the N/PME Earth from rising above 70V in the case of a broken suppliers N, you just use the existing earthing system for this method, as per the Niccys advice, if the building and services happens to be in fortuitous contact with true earth so much the better, but you are relying on a balanced system as the main method of compliance via exemption I)
Fine to a point, if you can balance the phases the chances of achieving a perfect or near perfect balance will in reality be neigh on impossible...
2) add additional rods to the PME MET to achieve the same ends, you need an extremely low Ra for this method at about circa 1 or 2 ohms, this is nothing to do with TT
This is the only real solution in my opinion!!
3) supply it from a 1:1 isolation transformer, meaning a fully floating supply
You cannot TT it due to the proximity of the PME bonded metal building
More dangers here than without an isolation TX. Not recommended!!
UK, have you not understood anything we have being saying to you ?
You have a few options,
1) ensure the three Phase supply is balanced according to the formula in the associated annexe with exemption I), and then it doesn't really matter how good the building is earthed to true earth, the load balancing alone will prevent the N/PME Earth from rising above 70V in the case of a broken suppliers N, you just use the existing earthing system for this method, as per the Niccys advice, if the building and services happens to be in fortuitous contact with true earth so much the better, but you are relying on a balanced system as the main method of compliance via exemption I)
2) add additional rods to the PME MET to achieve the same ends, you need an extremely low Ra for this method at about circa 1 or 2 ohms, this is nothing to do with TT
3) supply it from a 1:1 isolation transformer, meaning a fully floating supply
You cannot TT it due to the proximity of the PME bonded metal building
My comments in italics
Ok thats fine, same question goes to you, if the steel of the building is suitable, why can this not be used?
Ok thats fine, same question goes to you, if the steel of the building is suitable, why can this not be used?
tell me roughly where and ill look in mine and post a pic, just got mine 10mins ago1. I am just waiting for Amazon to deliver my book to day so will look at (i) then and calculate it.
2. I could put rods in, but what is it actually going to achieve on the basis the steel of the building is already doing the same job? I am not against the idea, but want a rock solid explanation as to how its any better than the steel work?
3. Where am I to buy one of them from? I do not know enough about transformers to even know if what I am buying is suitable in that respect, yes I know how they work, but have very little experience in using them and certainly not in this area.
I didn't say it couldn't, but you have no idea of it's standing value at the moment do you??
tell me roughly where and ill look in mine and post a pic, just got mine 10mins ago
Hi E54,
I don't make the rules lol
Option 2, using this method the additional rods need a low enough Ra as a standalone solution, you cannot rely or really take into account of any bonding connections as this could change and is outside of our control, in other words they have to be low enough Ra on their own to satisfy that exemption.
Option 3) Is valid according to the regs, whether that is a better solution is open to debate lol
yeah section 722 is "Electrix vehicle charging installations"Section 722.411 I think it was, then it refers to the an annex so you can calculate it something.
Were talking about a steel structure with maybe piled steelwork and a foundation slab that has steel reinforcement, (which could also be tapped and connected to the buildings MET) what would you honestly expect to change?? The DNO's TN-S, TNC-S, PME earthing provisions are out of our control too. The only earthing system that would be under local control is a made electrode TT system....
yeah section 722 is "Electrix vehicle charging installations"
He is the man signing the paperwork to say it complies and which exemption he is using.
trueIf you look there on that page at the bottom of point (i) it referrs to Annex 722 item A722.3, this is the bit we need to see I think.
Reply to Earthing for an EV Charging Point in the Electric Vehicles Advice Forum area at ElectriciansForums.net
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