Electric Vehicle Charge Point Install - Advice needed

Discussion in 'Electricians' Talk' started by Andy Neillans, Sep 3, 2018.

  1. Andy Neillans

    Andy Neillans New Member

    Afternoon folks,

    Looking for some sanity :)

    I've got conflicting information from my local (trusted) electrician, and a national company that is looking to install an EV charge point for me.

    We have already had our main fuse up-rated (and everything checked) from 40Amp to 100Amp ready for this work, and a year and a half ago had our CU replaced to switch everything over from the old style fuses.
    So far so good.

    The problem is our current CU is pretty full, even with leaving expansion in it during the upgrade (added a few electric under floor heating circuits since!) and we don't have any more planned work, so I'm not concerned there. There's a single spare breaker slot in the CU, and the EV installer is wanting to run the cable from it to the point. Which is a PITA as its on the other side of the house, will be floor boards up etc etc.

    My local spark has advised taking a sub-main and fitting a new CU next to the meter and isolator switch by the front door … literally right next to where the EV point would be installed - but the installer's are not happy with this.

    What's the best way for this? Is a sub-main a good option for a high load (32A) and completely avoid putting it up to the existing CU? Or should we putting it all through the single CU? If the spark's right, I've got no issues with getting him to the do the new sub-main install, then getting the EV point installed off that...

  2. Coloumb

    Coloumb Well-Known Member

    Why are the installers wanting a sub-main instead of a separate cu? What reasons did they give?
  3. Andy Neillans

    Andy Neillans New Member

    Installers are wanting to take from existing CU; which would involve a 30m run, and floor boards up, but guess electrically the easiest install?

    Local spark is suggesting a separate sub-main / CU (apologies if terminology wrong ;)) from feed - splitting the feed using Henley? blocks or just from the isolator itself ?
  4. Mr Rusty

    Mr Rusty Well-Known Member

    I think you are saying that your meter and isolator are not in the same place as your CU, which is 30m away. Seems a tad unusual. I'm no sparks but I expect the "national company" have a standard install detail which is to run a new circuit from the CU. Your unusual situation sounds like someone needs to think "outside the box" - hence the reason your sparks is suggesting a short sub-main and a second CU. I'll leave it to the sparks to suggest the correct technical solution.
  5. HappyHacker

    HappyHacker Active Member

    Based on what you have described I would go with installing a separate CU by the meter. There can be problems with this as the electricity companies often ban the fitting of customer equipment in "their" box. Get your electricity supplier to fit an isolator in the meter cupboard, issuing you do not already have one, so the whole installation can be isolated on one switch and enables the electrician to fit the new CU without working live or pulling the fuse (not usually allowed).

    Earthing is an issue with electric vehicle chargers and usually an earth rod is required but it depends on your earthing arrangement.
  6. Andy Neillans

    Andy Neillans New Member

    Spot on. The CU is in a bedroom cupboard upstairs, a good 30 - 40 meters cable run away.

    Personally I prefer the idea of a separate feed and CU downstairs for the charge point, as not only would it give us a better way of isolating it if need be, but also reduces the load on the main CU (which is heavy enough I'd think at the minute, as its fully populated). Not only that means not ripping up floor boards etc all through upstairs to run the cable to the point!

    Isolator switch already present - but no idea if its up to the job - or even how someone would be able to pull another feed from it to feed another CU - or if this will need to be replaced too :/ It's an old MEM style one (pic attached). Furthermore, as it's not currently in a meter cupboard or anything we shouldn't be stopped from changing or adding anything here :)

    Attached Files:

  7. peter palmer

    peter palmer Well-Known Member

    Slightly strange set up, why is your consumer unit not where the isolator is? because 30-40 meters sounds a hell of a run just to get upstairs to a bedroom. Is this isolator in a communal room as such? like a block of apartments etc.

    If its all in your private proerty I would certainly put a second consumer unit next to that isolator and break into the tails with a henly block or possibly upgrade the tails to 25mm if they're not already. Don't see any point in bringing a sub main back down from the upstairs fuse box, that would be a 60-80M circuit length and lunacy to do when there is a point you can take it from right next to it.
  8. Andy Neillans

    Andy Neillans New Member

    Tell me about it. This place has been a hell of a lot of fun (not) with the electrics. Nothing communal but ex-local authority 70's build where nothing was done "normal" it seems. When the central heating was done we had all the floor boards up, and was amazed how the conduit snakes its way up to the loft, back down, then around the upstairs to get to where the meter is :/

    Just measured the tails … looks like Scottish Power didn't look at them when they upgraded the head … they are only 10mm tails so guess I'll be onto the phone again to them tomorrow.

    Is it possible to get another set of tails from the current isolator (given the ones that run to the CU go into metal conduit), or is it going to be another isolator job (and somehow terminating the metal conduit)? Figure if that's the case I might as well get that done same time as tails are upgraded from meter etc.
  9. peter palmer

    peter palmer Well-Known Member

    I assume the incoming cable from the street goes into a 100A fuse and then straight to the meter, then I assume the tails go from the meter a short distance to the isolator.

    The isolator will have a fuse in it probably a 60A or so to protect the tails/submain going to the fuse box/consumer unit.

    The tails/submain size don't matter because they are protected by the fuse in the isolator so if they are only 10mm it sould be bad design to take the car charger from the upstairs fuse box anyway. Much better to wire it straight to the meter before the isolator with a little garage type fuse box.
  10. Andy Neillans

    Andy Neillans New Member

    Correct; looks like 10mm from head to meter, and 8mm or so from meter to isolator.

    Hopefully my spark gives me a call tomorrow and comes and pokes this lot to work out what needs to be done to get the feed for the point in :(

    Would it not be suitable to change the meter tails to 25mm, to a new isolator, Henley's then from there to current isolator and new garage style CU? I'd have assumed you'd still need some form of isolation before the additional CU, and that you couldn't remove the current isolator if its fused?

    Pic of the old head, meter etc. All except the head are correct.

    Attached Files:

  11. peter palmer

    peter palmer Well-Known Member

    I think strictly speaking you should have 1 isolation switch to kill the whole installation so that would mean an isolator straight after the meter before the henley splitter as you rightly pointed out. However me personally wouldn't bother doing that.

    I would replace the tails with 25mm from the head to the meter - even though this is the electric companies property- then 25mm to a henley, after that 16mm to the original isolator (25mm probably wont fit in the terminals inside it) and either 25 or 16 to a new RCD garage consumer unit with a 32A MCB feeding the charger.

    I'm sure I'll get flamed about the lack of a main isolator but I don't care. I've seen similar setups in their thousands up and down the country.
  12. Andy Neillans

    Andy Neillans New Member

    I get the feeling this is gonna be a bit of work ;) Hopefully my spark will be 'friendly' when it comes to doing the work to save me too much hassle with the DNO. Don't mind going to them to do their own part (head to meter), but everything else is a complete b---ache with isolating the circuits (had that problem with another property we had to get work done in that didn't have an isolator :/).

    Cheers for the input - will come back once I've had a chat with him!
  13. Lectrician

    Lectrician Screwfix Select

    Putting in a small CU by the meter would be the obvious choice, especially as you only have a 60amp submain to the main CU.

    Many of the OLEV electricians are people who have done a quick course to specialise in installing vehicle points, or electricians that were **** at everything else. They often cause problems.
  14. Bazza

    Bazza Well-Known Member

    I'm not sure you are correct in your measurements. Cable sizing refers to the cross sectional area of the copper conductor, not the outside diameter of the cable itself. Cable sizes are quoted in mm squared.
  15. Mr A greig

    Mr A greig Member

    Cables look small but I'm assuming if the fuse was upgraded then the tails and isolator are both rated for 100a?.
    I am definitely with the spark with this don't see why you wouldn't install a second cu Mr rusty is probably on the money, the installer will have a protocol that doesn't have any common sense written into it. I would opt for a decent size cu only about 50 quid and then you will have more options for wiring in the future.
  16. Andy Neillans

    Andy Neillans New Member

    Bazza - understood; those measurements were width - but even doing the csa calculations it still seems under sized. Looks like 16mm csa on the service head to meter - which would be acceptable I believe for the DNO side?

    I've got provider agreeing to install a new 100A isolator and uprated tails from meter to this; will then get spark to take this to connection blocks which can split to existing isolator (60A on 16mm2 tails) and a new CU probably also on 16mm2 tails. Spark tells me that there will be no need to put any fused isolator in for the CU that will be at meter.

    Phew. This has been a bit of a marathon with the installers changing their minds - and an awkward house ;)
  17. Mr A greig

    Mr A greig Member

    I've got two free 100a isolators from two smart meter installs. Eon and bg. Just a thought if your considering switching supplier at all.
    Personally I would ask he installs old isolator by old cu to avoid potential confusion. Don't think it's essential but more convenient and would mean that when you look at the cu you know the isolator next to it actually turns it off.
  18. Andy Neillans

    Andy Neillans New Member

    I had thought that, but the extra work is high in that case - as by the meter that isolator also terminates the steel conduit (and provides the fused protection of the feed).
  19. Lectrician

    Lectrician Screwfix Select

    Yea, they look like 16mm to me. Judging by reference to other things in shot.
  20. spinlondon

    spinlondon Well-Known Member

    Some friends of mine recently had a charging point installed, just outside their garage on their driveway.
    The charger is fed from the recently installed CU in the garage.

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