Rules and Guidelines
Want to participate in the discussions? Please read our Community Rules and Guidelines. Need some help? Visit Support and Answers.

  • State Not Answered
  • Locked Locked
  • Replies 15 replies
  • Subscribers 32 subscribers
  • Views 2043 views
  • Users 0 members are here
Options
You may also be interested in
This discussion is locked.
You cannot post a reply to this discussion. If you have a question start a new discussion

Another "EV Charger mounted on a metallic building with PME supply" question

Former Community Member
Former Community Member
Hi All,


I'm new to the forum, but not new to being a sparky, but through it was time i got online and got involved in the community. I know this previously came up on this thread in the previous incarnation of the forum, but the OP finally resolved to move the EV points further away from the metallic building, so it didn't really get answered.

Firstly, i am an experienced sparky and an OLEV approved EV chargepoint installer with many installs under my belt, but i've been working up from installs in homes and small businesses knowing this question would come up one day - now that time is here.

I have been asked to install a double socket single phase charge point on this commercial unit which is metal clad (this is really the only option for a place to put the pint without massive excavation through the car park which is many sim of tarmac. It's a large industrial unit with a TN-S 3-phase supply, approx 500kVA demand after diversity. The point is coming from a sub board near the location of the charge point (about 15m). The only issue is the fact i need to assume the TN-S could be PME as the DNO will not guarantee otherwise, but the metal clad building is obviously bonded to the PME terminal. The customer does not want any additional structures or enclosures putting up, the loading can not be guaranteed to be balanced as there is various equipment starting a stopping all day on different phases which discounts 722.411.4.1(i), and there is literally no open ground for at least 150m so i've discounted 722.411.4.1(ii), so this only leaves Electrical separation as a protective measure against an open neutral fault as far as i can see. I have 2 questions:


1. Am i correct that this is the only option? Is there anything else i should consider. I have a quote for the transformer and it isn't too expensive, and although it will need a bit of manhandling in to place at 80kg, it's a viable option. But i know a lot of people have concerns over this method in practise.


2. In the CoP for EV Charging Equipment Installations 3rd Ed., Figure 5.3. it shows the CP for the EV charge point originating from the N between the transformer and the RCD for the chargepoint. Doesn't this contradict 722.312.2.1 in BS7671, as its effectively a PEN conductor at that point? Or does 722.413 override this?


Cheers


Lee


P.s. question 3. in addition, surely the risk here isn't any greater than with the EV chargepoint installed that without, and someone standing on the same tarmac and leaning on the buildings steelwork or cladding? I obviously want to meet the regs, but isn't there something missing for this sort of situation which will likely become more common in the next few years.
  • 0

    2. In the CoP for EV Charging Equipment Installations 3rd Ed., Figure 5.3. it shows the CP for the EV charge point originating from the N between the transformer and the RCD for the chargepoint. Doesn't this contradict 722.312.2.1 in BS7671, as its effectively a PEN conductor at that point? Or does 722.413 override this?



    I wouldn't have said it was a PEN conductor (partly because it's not reliably earthed, partly it's doing the same job as the N-PE link in a true TN-S system - which by definition can't have any PEN conductors) - I do however agree that the diagram (if it's the same one as in the DPC for AMD1 of BS 7671:2018) looks nothing like a separated system and contradicts many of the fundamental requirements spelled out in section 413 - with the result that it won't passively remain safe under some first fault conditions like a separated system should but instead relies on protective devices - i.e. it's actually ADS and should be treated as such. If you add in that the charge point (if class I construction) and/or vehicle under change may have fortuitous connections to true earth, it doesn't obviously look to have any reliable advantage over a local TN-S system, or even just TT'ing the charge point.


       - Andy,
  • Former Community Member
    0 Former Community Member
    I hear that a manufacturer has now made an EV charger that can be installed to PME systems. (myenergi - zappi - other manufactures may manufacture something as well). I've not installed one of these, but they say it's compliant with the reg 722.411.4.1 (iii)

    Might be worth a look.
  • 0
    It may be that by the time you need to install this, you will be allowed to use the PME earth providing you can supply the charger via a contactor that disconnects all conductors, including the CPC,  if the line voltages go out of spec enough to indicate a supply side fault.

    If you look at the post this morning about the new draft COP for charging and follow the link - you do have to give a name and address and an Email, but as far as I can tell they are not checked, then you can view the COP in a sub window, and even save a copy to view locally (though the watermarkings ask you not to) Anyway, this allows the use of an "Open PEN detector" and refers to an yet to be included section 722.411.4.1 (iv) in the regs, and then describes a voltage operated device for installations with single-phase supplies, that operates when the line to neutral voltage at the charging point is outside a specified range.

    For 3 phases, the voltage between the phase centre and a reference electrode can be used, again to fire an all-pole LLLNE trip.


    This is a change that will I think make charging possible in cases like that you describe.

  • Former Community Member
    0 Former Community Member

    Naj93:

    I hear that a manufacturer has now made an EV charger that can be installed to PME systems. (myenergi - zappi - other manufactures may manufacture something as well). I've not installed one of these, but they say it's compliant with the reg 722.411.4.1 (iii)

    Might be worth a look.






    Yes, both the Zappi and at least some PodPoint charge points have these devices. I know that the pod point ones (some at least) have earth rods, so i can only assume they have a device similar to that described in 722.411.4.1 (iii), where they are measuring the voltage between the PME and earth which disconnects if it is greater than 70v for 5 seconds.


    My only issue is that the Zappi isn't suitable for this install as it's not the right product and also isn't applicable with the OLEV, and PodPoint only really install their own points. It would be great for someone to market and mass produce this device above so we can install them instead. I would do it myself if i was in the right position to start another business! Lol.

  • Former Community Member
    0 Former Community Member

    mapj1:

    It may be that by the time you need to install this, you will be allowed to use the PME earth providing you can supply the charger via a contactor that disconnects all conductors, including the CPC,  if the line voltages go out of spec enough to indicate a supply side fault.

    If you look at the post this morning about the new draft COP for charging and follow the link - you do have to give a name and address and an Email, but as far as I can tell they are not checked, then you can view the COP in a sub window, and even save a copy to view locally (though the watermarkings ask you not to) Anyway, this allows the use of an "Open PEN detector" and refers to an yet to be included section 722.411.4.1 (iv) in the regs, and then describes a voltage operated device for installations with single-phase supplies, that operates when the line to neutral voltage at the charging point is outside a specified range.

    For 3 phases, the voltage between the phase centre and a reference electrode can be used, again to fire an all-pole LLLNE trip.


    This is a change that will I think make charging possible in cases like that you describe.

     




    Sorry, i read this after my previous last post. I'm just reading the new CoP (thanks for that), and it seems an expansion of the section I mentioned previously. I'm looking at early to mid December for this install, so hopefully someone has a nice product on the market by that time (or i can concoct something myself before then!). Anyone feel free to contact me if you invent something! 

  • Former Community Member
    0 Former Community Member
    I found these: https://matt-e.co.uk


    They're marketing O PEN, a open PEN detector.
  • 0

    Anyway, this allows the use of an "Open PEN detector" and refers to an yet to be included section 722.411.4.1 (iv) in the regs, and then describes a voltage operated device for installations with single-phase supplies, that operates when the line to neutral voltage at the charging point is outside a specified range.



    I've got some worries about how reliable these can be when there's 3-phase distribution upstream of your single phase installation. If my O-level maths and back of an envelope phasor diagrams are anything like right, I think it's possible (with the wrong combination of loads on the various phases) to have the severed PEN hovering at more than 100V above Earth, but still have a nominal 230V L-N at the charge point.


    If you have access to all three phases it's a lot easier to reliably work out (without using an electrode for reference) if the the PEN is drifting away from earth potential - as you can generate an artificial N point to compare with (provided all three lines are still connected).


      - Andy.
  • 0
    One other thought (sorry, going off at a tangent now) ... should these devices be subject to any testing? (either on testing or during periodics). I guess they'd share some basic technology with RCDs (current/voltage sensing, comparison with a threshold and triggering mechanical contacts) - and if after all these years RCDs are considered vulnerable to failure should we not take similar precautions with these new devices?


    I guess a variac and a stopwatch would do - but maybe there's a market for a new kind of tester...


      - Andy.
  • 0

    If my O-level maths and back of an envelope phasor diagrams are anything like right, I think it's possible (with the wrong combination of loads on the various phases) to have the severed PEN hovering at more than 100V above Earth, but still have a nominal 230V L-N at the charge point.



    Indeed, and yet for the 3 phase case they insist on the reference electrode method, which might be more germane for single phase.

    Still both the change to the regs and the COP are still at the stage of a draft for comment, so you (like me) can get your thoughts in now.

    ( Deadline for return of comments is Saturday 30th November 2019. )


    As regards testing, there is quite a lot in the charger itself to test as well, how much of that do we test with the fixed  wiring, and how much should we treat  it more like an appliance ?
  • Former Community Member
    0 Former Community Member

    AJJewsbury:

    One other thought (sorry, going off at a tangent now) ... should these devices be subject to any testing? (either on testing or during periodics). I guess they'd share some basic technology with RCDs (current/voltage sensing, comparison with a threshold and triggering mechanical contacts) - and if after all these years RCDs are considered vulnerable to failure should we not take similar precautions with these new devices?


    I guess a variac and a stopwatch would do - but maybe there's a market for a new kind of tester...


      - Andy.




    I know Metrel have developed a 6mA DC earth leakage test cycle on their testers to ensure this is working on you charge point, they demonstrated it to me at a trade show recently. The rep told me they anticipate this becoming a requirement in BS7671, so I would think it’s only a matter of time... 

Join us to get the best from IET EngX.

Joining EngX lets you personalise your experience so you stay up to date on the topics that interest you, plus you’ll be able to make connections who are looking to collaborate, exchange ideas and more.

Join us Not now

Community Rules & Guidelines