SIMULTANEOUS CONTACT QUESTION - 2 x EV vehicles parked next to each other

Scenario

A remote block of 3 garages, 2 will be fed from separate properties via 40m of 10mm EV SWA connected to 2 individual new CU's

( no cars will be parked inside the garages but charged on the drive in front of the garage door)

1 property is TNC-S - Ze 0.30 Ohms and the other is visually a TNS but with Ze 0.32 Ohms and similar L-N reading.

The 2 chargers will have Pen fault protection and the relevant RCD protection as usual.

There are underground services within 1 -10m of a potential TT rod so could be problematic and a maximum 2.5m between separate garage earth rods is possible.


The concern is simultaneous contact between the 2 vehicles.

Regulation 411.3.1.1 states that “simultaneously accessible conductive parts shall be connected to the same earthing system individually, in groups or collectively.”

I am currently waiting for UK Power networks to confirm the 2 properties are connected to the same earthing system.


The questions are:

Is Pen fault and RCD protection enough when connecting both cars to TNS/TNCS or is there anything else we can do?

Is separate TT earth rods along with simultaneous risk assessment the safest option in this case?

Thank you


I've attached a sketch of the current proposal to help explain.
PDF

Parents
  • Dean,

    Obviously as you have indicated and good advice from Graham, and maybe its a remote option that could be considered.

    And that would be to install or erect some kind of "Wall/partition" between the two EV charging bays, to prevent similtaneous contact? Might not look pretty and obviously something a car could hit if not being carefull, but if done correctly could perhaps give an option if UKPN confirm the worst, just need to consider the fire rating and combustible nature of any "Wall/partition".

    Cheers GTB 

  • Are we not even allowed to have wooden fences near an EV charger now?

  • Thank you GTB, this could be an option, i was also thinking of maybe putting 2 chargers on one property with load balancing. One of the clients could use RFID to charge the cost to the main electricity account holder. 

    Just another thought!

  • Are we not even allowed to have wooden fences near an EV charger now?

    That might depend on your insurance company's perspective ... and that is not said in jest ... but BS 7671 of course doesn't really have any beef with it.

  • Morning Simon,

    Its something that is cropping up far more often now, and also in the small print of terms and conditions of building insurance policies, that I suspect vast majority of people dont even look at.

    Most UK Insurers refer to the FPA RC59 document and guidance and detail in that.

    There is advice when installing charging bays about Min seperation distance to adjacent vehicles but also from properties.

    Because of the jet like flame that could possbly come from a lithium ion battery there is detail about distances from building structures. I have seen some policy terms now that although they obviously cant state that EV charging is not allowed or covered as part of the policy, many are indicating "Charging" needs to take place 10M from a domestic property!!

    Its to do with heat froma potential EV car fire and the impact on the windows and doors of the property and the fire protection offerred by those being defeated.

    Thats why I suggested if a wall/partition was being placed between two charging bays, where EV is being charged from two seperate supplies and earthing arrangements, I would have that wall/partition of suitable non combustible material.

    GTB 

  • This is interesting, because the particular job this original thread refers, the garages are a wooden structure! Seems like everything is against this job.

    What happens in that case?

  • What happens in that case?

    Some insurers have terms that require a certain distance from combustible materials [some include shrubs, trees etc in that definition] from which EVs must be when on charge.

    The IET Code of Practice refers to an industry publication RC59 Fire safety when charging electric vehicles, which can be freely downloaded here: https://www.thefpa.co.uk/advice-and-guidance/free-documents?=%20Medium-sized%20Businesses,%20MAINTENANCE%20CHECKLISTS%20-%20APPENDIX%20TEMPLATE%20FORMS,%20CONTROL%20OF%20DUST%20EXPLOSIONS&q=RC59%20FIRE%20SAFETY%20WHEN%20CHARGING%20ELECTRIC%20VEHICLES

    The difficulty for designers is that insurance company terms vary, and they don't all align fully to RC59 ... so this is something that should be discussed with the Client(s) prior to the design being finalised.

  • Hi Graham

    Thank you for this info.

    I contacted earthing services today ( very helpful guy), he said with one separate condudisc/earthing conductor per garage situated 2.5m apart and connected together in the ground at 600mm will achieve 53 Ohms( with this post codes soil resistivity).

    He also said if one client disposes of their charger/garage supply it still leaves the other with a 53 Ohms earth resistance.

    The condudisc has a life expectancy of 408 years if embedded in conductive concrete, would this be an compliant option if UKPN do not commit?

    Kind regards

    DeanW

Reply
  • Hi Graham

    Thank you for this info.

    I contacted earthing services today ( very helpful guy), he said with one separate condudisc/earthing conductor per garage situated 2.5m apart and connected together in the ground at 600mm will achieve 53 Ohms( with this post codes soil resistivity).

    He also said if one client disposes of their charger/garage supply it still leaves the other with a 53 Ohms earth resistance.

    The condudisc has a life expectancy of 408 years if embedded in conductive concrete, would this be an compliant option if UKPN do not commit?

    Kind regards

    DeanW

Children
  • He also said if one client disposes of their charger/garage supply it still leaves the other with a 53 Ohms earth resistance.

    The point I was making wasn't simply about "disposal" of one earthing system, but more the maintenance of the bond between the two if the two chargers are to keep operating under the same conditions.