EV charger installation and fuse upgrade questions

itm2

We're planning to get an EV charger installed. I've just ordered a Zappi Glo, and am getting quotes for installation. There is a complication in that our main fuse is 60A and we've been advised that we will need to get it upgraded to 100A. This in turn will involve getting our main tails upgraded from 16mm to 25mm.

I'm trying to make sense of various bits of guidance/advice that I've been given, and would be grateful to hear from anyone who has been in a similar situation.

My questions are:

• Who is allowed to replace the main tails from the incoming supply/main fuse to the meter, and from the meter to the henley blocks which link it to my 2 consumer units? (i.e. does this need to be done by my energy company (Octopus), my DNO (UK Power Networks), a combination of the two, or can it be done by the electrician installing the EV charger?
• What level of approval do I need from the DNO for the EV charger installation, and when do I need this approval (e.g. can the install go ahead before approval, subject to temporary limiting of the EV charger's load if necessary prior to approval)?
• Are there any mandatory certifications which I will need for this work to be carried out legally?

born_again

Your installer should sort all that out & gain the required DNO approval & safety paperwork for you.

Although they may not be able to upgrade the main fuse.

Keep_pedalling

Any changes to your tails will need to be done by the DNO.

Myenergi charge points can be configured to provide dynamic load balancing (restricting the power draw on the Zappi when their are other demands from other devices) so it should be possible to get it installed and used before an upgrade takes place.

jaybeetoo

You are unlikely to get a 100A fuse as 80A seems to be what National Grid and other DNOs are installing.

Keep_pedalling

https://forums.moneysavingexpert.com/discussion/comment/82100883#Comment_82100883

16mm is sufficient for 80A, I wonder if the OP actually has a looped supply?

itm2

https://forums.moneysavingexpert.com/discussion/comment/82100896#Comment_82100896

I've been trying to calculate my worst case scenario, in terms of maximum load. I'm planning to switch to the Octopus Intelligent Go tariff to make use of the cheap overnight rates. For that reason, my peak usage will be during that overnight window.

So for example;

• "Normal" overnight house load (as observed from the solar inverter stats and Octopus data: 0.7kW
• Air conditioning in bedroom: 1.1kW
• EV charger: 7.4kW
• Solar battery charging: 7kW
• Washing machine: 2.4kW
• Dishwasher: 2kW
• TOTAL: 20.6kW

Which equates to 85.83A? Obviously that won't be the normal load, but it's a plausible worst case scenario.

QrizB

There is a complication in that our main fuse is 60A

I'm surprised that that's seen as a complication; my installer was unable to check the rating of my fuse, and so capped the total current drawn in software. If I'm drawing 28+ amps for the rest of the house, my charger will limit its output so as not to exceed 60 amps total.

Who is allowed to replace the main tails from the incoming supply/main fuse to the meter, and from the meter to the henley blocks which link it to my 2 consumer units?

Look at the colour-coded guide on page 3 of this SSE Networks document:

https://www.ssen.co.uk/globalassets/our-services/connect-1-4/site-readiness-guide-small-connections-1120-3.pdf

The fuse-to-meter tails are the responsibility of your supplier (Octopus) and everything after the meter belongs to you.

Having said that, I hear that some electricians will happily pull DNO fuses and cut seals on meters …

itm2

Thanks for the feedback. I'm wondering if the following sequence of events would work:

1. Electrician upgrades consumer tails from 16mm to 25mm and installs EV charger at the same time. Also limits the power draw of the Zappi charger temporarily.
2. Octopus upgrades meter tails to 25mm
3. UK Power Networks checks the above and upgrades the main fuse from 60A to 100A

Does that sound plausible?

born_again

https://forums.moneysavingexpert.com/discussion/comment/82100916#Comment_82100916

Remember that IOG is not just a cheap overnight tariff. It also offers daytime slots @ off peak rate. To a max of 6 hours in a 24 hour period ( lunch time to lunchtime)

Mine is connected up at the moment (ready by 07:00) for a 10% or 8kWh charge. So far had 15:30 to 16:00 & the rest is schduled for 01:30 to 02:00 & 06:30 to 06:46

I do not schedule anything in the car. Just let OHME & Octopus work out when to charge cars.

lohr500

Sorry for jumping in on this, but I find myself in a similar boat although not quite the same!

When Pod Point looked at the photos I sent of my meter set up last week, they concluded I was on a looped supply and so needed to get pre-approval from the DNO before they could schedule an installation.

Background :

Our property is at the end of a high voltage 3 phase overhead power line which spurs of another overhead 3 phase power line approx 600 meters away. There are no other properties tapped off the high voltage spur.

Mounted on our pole is a transformer which appears to have one tap going to earth down a cable attached to the pole, The other tap on the transformer brings a feed to our house via a single overhead cable which ends up connected to the live terminal on our main fuse box.

The main fuse box is fitted with a 100 Amp fuse which as far as I am aware has been there since the now defunct YEB installed the supply many, many years ago.. All the mains cables are 25mm already. It was confirmed as being a 100 Amp fuse when the Tesla installer pulled it last year 😏

The neutral side of the main fuse box has a separate thinner cable which passes through the wall of the house and disappears underground through some concrete.

I can't see how this thinner cable is anything to do with a looped supply because we have no neighbours within 600 yards and no outbuildings with separate meters.

A YEB label on the fusebox says the earthing terminal on the fuse box is connected to a protective multiple earthing network.

My theory is that the neutral cable from the fuse box which disappears underground actually goes to earth and we have a system with earth and neutral connected together. The house also has a separate earth rod with an earth cable connected to a busbar near the fuse box. Also connected to the busbar is an earth cable from the side of the main fuse box and other earth cables from the consumer units, etc.

I contacted the DNO in response to some questions they had following them being contacted by Pod Point and explained all the above.


Anyway, the DNO has replied today confirming approval to install the 7.4kW EV charger with no additional work required.

BUT, they have specified a maximum capacity of 14kVA/60 Amps.

Limiting whole home load to 60 Amps will result in a period of 2.5 hours, where there will only be 10 Amps surplus for the EV charger. This because our battery storage, electric AGA and other base load draw 50 AMPS over the first 2.5 hours of our off-peak period.

Effectively the 7kW EV charger will be throttled back to charging at +/- 2.4kW for 35% of our 7 hour off-peak period.

I can't modify the charging rate for the battery storage as this is controlled by Tesla's built in logic and the AGA needs the full 7 hours off-peak to fully reheat.

I've gone back to the DNO today asking if the maximum capacity of 60 Amps does apply to the whole house and if so why? There was no investigation over the maximum capacity when they approved then G99 request for the battery in 2025 and the approval just said Import capacity = "as Existing".

Given that we already have a long established 100 Amp main fuse and 25mm tails on all the mains cabling, I can't understand why they have set the 60 Amp limit.

Hopefully I can get a positive response back from them before the scheduled EV installation date of 25th August.
I really would prefer the installer not to set the whole house load at 60 Amps in the charger settings.

I've also gone back to the Pod Point installation team to get their take on this.

Keep_pedalling

if you are on a looped supply you won’t have a 100A fuse even if says 100A on the fuse holder which is actually the hurst fuse rating the holder can take. Ideally you need de looping and have a three phase supply installed.