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    Before I close up my ceilings I am thinking to install the cable I might need for a future electric car charger installation. The consumer unit is in the middle of the house but I can run the cable along the first floor joists to the outside wall. Or behind the skirting. I have no idea of which cable will be suitable. Does anyone have experience in this?
    • CommentAuthorrevor
    • CommentTimeJun 28th 2022
    I presume you will be wanting to install a 7kw charging point which will be ca 30 amps. What size cable you use will depend on how long it will be so you are looking at minimum of 6mm possibly 10mm. You should not run it behind skirtings or anywhere where it is not obvious there is a cable present. There are rules for cable runs so google "safe" zones for cable runs or something similar.
    Do not have it in contact with or go through insulation to avoid overheating. Depending on the cable you will be looking at 32 amp CB for 6mm and 40 amp for 10mm. The load is akin to a shower. You will find a calculator here.


    There are other calculators available. If in doubt get an electrician to advise. It won't be a DIY job to install the charging point there are special requirement w.r.t installing chargers particularly earthing.

    To give you more flexibility w.r.t the choice of chargers it may be prudent to also run a cat5e or cat 6 data cable to the intended outlet position from your router but keep it about 300mm or more away from the mains cable.
    • CommentTimeJun 28th 2022
    What revor said. It will need its own way in the CU with its own RCD. I'm not sure how needed an Ethernet cable will be; all the latest chargers I've seen have wi-fi and/or a SIM, but you may as well put a data cable anyway.

    The installation needs to be pukka. Remember it will be pulling 30A for many hours at a time each time it is used, not just a few minutes as with a shower or similar.
    • CommentAuthorLF
    • CommentTimeJun 29th 2022
    Revor - Good point general about ethernet cable being segregated away from a parallel power cable so it does not pick up /induce interference. Shielded cables can presumable help.
    • CommentTimeJun 29th 2022
    Posted By: LFShielded cables can presumable help.
    Not as much as you might think. They're not usually required in a domestic setting and their earthing requirements can complicate things quite a bit. Plus of course they are more expensive. Bit like Cat 6 with its increased bend radius; not worth it unless you're going to use it IMHO.
    • CommentAuthorJonti
    • CommentTimeJun 30th 2022
    Why not just install an empty conduit so you can pull a cable through in the future if needed.
    • CommentAuthorjms452
    • CommentTimeJun 30th 2022
    You can get power and data in the same cable which makes a neater job where the cable runs externally.


    also aligns with:

    Posted By: JontiWhy not just install an empty conduit so you can pull a cable through in the future if needed.
    • CommentTimeJun 30th 2022
    But note that there's only one pair for data, not the four required for Ethernet.
    • CommentAuthorcjard
    • CommentTimeJun 30th 2022 edited
    >I have no idea of which cable will be suitable

    Installing a new circuit is notifiable work; by all means do it yourself, but you must have the installation approved by your local authority building control (if you can get them to do it). It would be simpler and safer, for a single cable run, to get an electrician to do it and self-sign it off.

    > Or behind the skirting. I have no idea of which cable will be suitable

    I genuinely have no desire to be insulting, but both of these statements really do outline the level to which you're NOT currently equipped with the prerequisite knowledge to do this work. This isn't something you take a few lines of advice for off strangers on the internet; this is something that electricians study and train for and are then examined on and engage in continued professional development for so they remain up to date

    Note, that it's not really about "put a cable on the ceiling and I'll get a sparky to connect it up in 5 years" - the cable choice and route is the critical part; it'd be more sensible to get competent professional advice right now as to which cable and what route it should take, if you plan on connecting it later. No awake sparky will want to connect up a cable they didn't install, or at the very least cannot see the full length of

    > Do not have it in contact with or go through insulation to avoid overheating

    It is allowed to come into contact with insulation, but the installation method chosen must be suitable for the required current carrying capacity

    > it may be prudent to also run a cat5e or cat 6 data cable to the intended outlet position

    Yes, though honestly, for the minimal data bandwidth requirements a car charger has it'd be just as well served by hiding a powerline ac/ethernet adapter inside the case and another one plugged in near the router

    > Why not just install an empty conduit

    Possibly the most sensible advice for the current situation, IMHO. Make it a large duct (75mm mvhr flexi, perhaps) because ducting affects the current carrying capacity of a cable; if your future electrician decides the in-duct installation method requires a cable with an outer diameter larger than the inner diameter of your duct, then there ain't much point installing the duct..
    • CommentAuthorjfb
    • CommentTimeJul 1st 2022
    I would stick a 6mm cable in.
    It isn't rocket science to find a suitable route for a cable run to go. Just be aware of safe zones, rules for joist drilling/notching, avoid encasing in insulation (better to have insulation on just one side if possible) and take lots of pictures.
    I will qualify this by saying that I am not a qualified electrician but that wouldn't prevent me feeling confident about doing it.

    Is it a new build? Do you have an electrician doing the rest of the build and why can't you ask them what they think?
    Id go 10mm T & E , that will let you go up to 10Kw at 15m run easily
    6mm is a bit tight on longer runs

    many of the newer units dont need data connection

    • CommentAuthorrevor
    • CommentTimeJul 1st 2022
    Strictly speaking you should have a first fix pre-plasterboard check on cable runs before it is enclosed. This is to ensure the cable is of correct rating for job and is run in accordance with BS7672. When I wired my house I went through building control and had my work inspected and passed by an electrical company before plastering. As the EV point is a specialised install and you will need a qualified person to do it you might as well engage one now as it would be cheaper than going through LABC. It is not a simple outside power point socket as mentioned there are earthing considerations specific to EV charging points.
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