Incoming mains capacity - ping Adam

[Roger Mills]

I'm trying to ascertain the capacity of my incoming mains just in case I acquire an electric vehicle at some time in the future (no immediate plans) and wish to install a charge-point.

The incoming head/main fuse looks like this:

The OD of the (painted white) cable entering from the bottom is about

14mm. I'm assuming that this is TN-C connection with a copper concentric cable - in which case the live conductor is likely to be 25 mm^2.

But the thought occurs to me that it just could be a TN-S supply with a split concentric cable - in which case the central conductor would only be 16 mm^2. Is there any way of telling which it is without breaking the seals on the head and fuse, and looking inside?

The tails from the head to the meter and thence to two consumer units have an OD of around 11 mm - suggesting that they are 25 mm^2 - so I'm hoping that the incomer is, too. I don't know what size the main fuse is without breaking the seal but presumably, if it's less than 100 amps, it could be upgraded to 100 amps as long as the incomer is 25 mm^2?

[Jimk]

Is this the grade 2 holiday home project lead project or at home?

[Roger Mills]

This is my main home. But the fact that we're looking at it for the flats prompted me to think about it here, too.

[ARW]

Probably a 60A fuse. Almost certainly TN-S with split concentric cable as there is no yellow PME sticker.

Open it up and have a look. Take some photos for the wiki to add to

and I'll send you some meter seals to make it look OK.

Not got the paper ones that say "It is an offence etc" just the strip and lead crimps. Cig lighter fluid removes them.

[Tim+]

The thing to remember is that a standard domestic EV charger will draw no more than an anaemic electric shower. ;-). There really isn?t isn?t much point in going for higher than 7kW if you can charge overnight.

I reckon you?ll be fine.

Tim

[Roger Mills]

I'm not sure where this is leading. Have you got anything useful to say in answer to my original question?

[Roger Mills]

Yes, indeed. And the 'smart' ones can monitor the current passing through the meter, and throttle back the charging when there are other high demands.

But I'd still like to understand what I've actually got. The original house was built in the 1960's and, although I've replaced the original "fuse box" with a consumer unit with MCBs and an additional CU has been installed for the new kitchen, the mains supply itself has never to my knowledge been upgraded - unless the fuse was changed when the analog meter was replaced by a digital one.

[Roger Mills]

What's to say that we - or future occupants - may not have 2 or 3 EVs, and need to charge them all at the same time? No harm at looking at options, and understanding where the constraints are!

Fortunately, Adam has come back with a much more useful answer - as I hoped he would.

[John Rumm]

as an aside, we probably ought to put a section in that wik article on PME stickers, with an example photo etc.

[Martin Brown]

Or an old electric cooker and most domestic supplies cater for that.

Presumably that requires that you have a smart electricity meter. I can't see my prehistoric counter rotating cogs and dials meter talking to anything. Most meter readers struggle to read it - the thing is right up near the high ceiling in a dark narrow hallway.

Probably 60A then from the date. One thing to watch out for if the wiring is still all original is that the electricity board might want to degrade your main fuse to 40A when they install a smart meter as happened to a friend (whose house was built late 50's and still has mostly round pin sockets!). Keep on nagging them to get it rewired...

[Jack Harry Teesdale]

It is most likely to be a minimum of 60A capacity which should be more than enough for an electric car charger unless you have electric night storage heating.

If you need a more authorative answer you could check with your DNO, which i did recently when considering installing an electric boiler, they were very helpful.

[Roger Mills]

No, I don't think you need a smart meter - which I'm resisting, anyway. AIUI, it doesn't need to 'talk' to the meter - it simply has a current sensor clamped round one of the tails. I haven't actually seen one, but that was how it was explained to me by a potential supplier when I was investigating charge-points for the building of which my second home is a part.

[Andy Burns]

No, the throttling is not done by the meter, it can be done by some cleverer EVSEs (the box on the wall that you connect to the car, and which tells the onboard charger how much current it is allowed to draw).

[Tim+]

That?s what my Podpoint has. You?re quite right in that you don?t need a smart meter, but you?ll almost certainly save money on charging if you do as you can move on to a variable rate tariff with cheaper off-peak overnight rates when you?re charging your car. Of course this is offset by higher rates at other times but at least you can choose when and how you use your electricity and try to avoid car charging or other high usages during peak times. I?m getting one next month (having previously had no real reason to get one).

Tim