Welcome to Tesla Motors Club
Discuss Tesla's Model S, Model 3, Model X, Model Y, Cybertruck, Roadster and More.
Register

DNO issues with charger install

Tallboy

Member
Oct 27, 2019
14
4
Sutton Coldfield
Hi everyone.

I’ve got a model 3 on order, but am having issues with my DNO.
My house only has a 60 amp supply, and as it’s old, I can’t just increase it by changing the fuse.
To install a new cable, they’ve quoted around £4000, plus builder costs to dig up my driveway, and electrician costs to move the meter and change the wiring.
Without doing all that, they won’t give me permission to have a charger installed. And I don’t have the approx £7000 sitting around right now!

I’ve given them solutions, like using a Zappi which has a device called a Harvi which can measure the load coming into the house, and reduce the charger output to keep it within 60 amps. And also said that I’ll only charge at night when no other high load units are switched on, but they still demand extra specifications that the Zappi doesn’t have.

Does anyone have similar circumstances and found solutions?
 

gangzoom

Active Member
May 22, 2014
1,357
1,212
Uk
Why cannot you install a 32amp commando socket and use the UMC to charge the car? Took an electrician 30 minutes to fit ours cost £50.
 
  • Like
Reactions: ringi

Glan gluaisne

Supporting Member
Supporting Member
Sep 11, 2019
2,782
2,912
UK
Another option is to get a priority unit installed. These are common in Ireland, where supplies are often around 60 A max, and they were introduced to allow an electric shower to be used with an installation where normally this might overload the incoming supply. Garo make a range of units for different options that have everything in one enclosure: Search Results

(I have no connection with Garo, but have installed one of these for a friend, some time ago).

These work fine for overnight charging, as usually the house load will be fairly low overnight, so the 32 A drawn by the charge point (which is treated as an electric shower as far as the Garo unit is concerned) can be comfortably accomodated. The DNO should be happy as long as they know that a load limiting relay has been installed.
 
Last edited:
  • Informative
Reactions: Roy W.

Adopado

Active Member
Aug 19, 2019
4,313
3,258
Scotland
You'll get your definitive answer if Arg sees this thread! From the amateur viewpoint it does seem that you could work within 60amp but rules is rules ... and Arg knows those rules!
 

VanillaAir_UK

Well-Known Member
Jun 17, 2019
8,480
6,022
Surrey, UK
I was told that they could not refuse the first install. I may be very much mistaken, but I believe that they were responsible for some of the remedial work (up to the meter) to ensure that the supply was up to scratch - but I guess it depends where that remedial work is needed and how much of it crosses over/under your land.
 

Glan gluaisne

Supporting Member
Supporting Member
Sep 11, 2019
2,782
2,912
UK
The problem may be that the installer cannot fit a charge point without the combined load exceeding that of the supply, so, instead of looking at other solutions, a request has been made to the DNO to upgrade the supply.

It's pretty simple to just fit a priority unit to allow a 32 A charge point to be fitted to a 60 A installation. Doesn't add much cost, either, as the priority unit includes a Type A RCBO, which would likely be needed anyway. All that's needed is to look at the highest load on the existing installation (probably either an electric shower or the cooker feed) and connect that via the priority unit.

The way this works is pretty simple. If the existing high power load (shower or cooker most probably) is in use, and demanding more than ~3 kW, then the charge point supply will be turned off. Under all other conditions the charge point supply will be turned on.

These Garo units weren't originally intended for use with charge points, but there was an advert in one of the trade mags earlier this year where they had started promoting their use for this purpose. They seem like an ideal solution, it's just that word hasn't really got around about them here in the UK yet.
 

Jason71

Active Member
May 8, 2019
3,074
3,079
Shropshire
Western power my DNO told me:
"
If the total is less than 60A submit a notification form to the DNO
If the total is greater than 60A submit an application form to the DNO
"
So if the installer can limit to to 16 amp ( which some can) and thus be confident it will not go over 60 amp the can fit it and then notify the DNO afterwards
 

Tallboy

Member
Oct 27, 2019
14
4
Sutton Coldfield
Thanks for the posts.

Some research for me then! I’ll look into the garo option, and see if my dno (western power) would be happy with 16 amps to start with.
A best case option would be a charger that could limit the current during the day, to say 10 amps, and then increase during the night to 32. We don’t have a power shower, and have GCH, so no large loads during the night at all.

I’m hoping Zappi May have this function.

As one of you mentions, I was told the can’t say no to a charger install, but I’m guessing the can make you pay for the work needed to get one approved.
Cheers
 

VanillaAir_UK

Well-Known Member
Jun 17, 2019
8,480
6,022
Surrey, UK
I think you will be surprised how much effort it takes to get to 60A load.

If you don't have a heat pump, or high power electric shower, or storage heaters etc, then I would think that for most, even if 32A continuous charging, the total house load will remain under 60A.

I've got power records going back 5 or so years and during that time, the most power we have ever drawn at any one time was just over 5kW. That was with a Christmas gathering with electric oven and induction cooking and a dishwasher running at some point. Lets call it 6kW so around 25A or 57A with 32A EV charging so within the 60A.

Unfortunately, some installers will just count up the Amps from your fuse box and base it on that.
 
  • Like
Reactions: SirRob

Glan gluaisne

Supporting Member
Supporting Member
Sep 11, 2019
2,782
2,912
UK
The problem isn't with whether in practice, the load ever gets close to the maximum the supply will support, it's with the calculated maximum load, allowing for diversity, as per BS7671.

I can't sign off an EIC for something like a charge point installation if I know that the sum of the loads, allowing for diversity, where applicable, exceeds the rating of the supply. A 60 A supply may well be able to support the actual demand, plus a charge point, but if the sum of the loads for each connected circuit exceeds 60 A then the installation is non-compliant.

The loads aren't hard to calculate, just means looking at the individual circuits and then doing the sums to work out the load for each. For example, each ring final circuit, on a 32 A MCB (or maybe a 30 A fuse) will be calculated as 100% of the total current up to 10 A, plus 50% of any current over 10 A, so for a 32 A MCB the calculated load will be 10 A + (22 A x 50%) = 21 A. For a lighting circuit the calculation is 66% of the total current, so for a normal 6 A MCB the lighting circuit load will be assumed to be 6 A x 66% = 3.96 A (rounded to 4 A). A cooker load will be calculated as being 10 A plus 30% of the current over 10 A, plus an extra 5 A if there is a socket on the cooker outlet, so for a fairly standard 40 A cooker circuit, with no socket at the switch, the load would be 10 A + (30 A x 30%) = 19 A.

The problem loads are heaters, like electric showers, or immersion heaters, where no diversity is allowable. A 9 kW shower will draw just over 39 A, and an immersion heater will draw just over 13 A, at the UK nominal 230 VAC supply. There's no diversity allowable for electric floor heating, etc, either. The same applies to a charge point, there is no diversity allowable, so the full current has to be used in the load calculation.

Here's an example calculation for a fairly typical house that has two 32 A power ring final circuits, two 6 A lighting circuits, plus a 40 A cooker outlet:

Each ring final is 21 A, so sub-total = 42 A
Each lighting circuit is 4 A, so sub-total = 8 A
Cooker circuit (no additional socket) = 19 A

Total = 69 A, so already over the maximum allowable for a 60 A incomer. The chances are that many houses on a 60 A supply may have either a restricted number of circuits, or have the maximum load on some circuits reduced, in order to stay within the supply limit.
 
Last edited:
  • Informative
Reactions: Adopado and Roy W.

VanillaAir_UK

Well-Known Member
Jun 17, 2019
8,480
6,022
Surrey, UK
I can't sign off an EIC for something like a charge point installation if I know that the sum of the loads, allowing for diversity, where applicable, exceeds the rating of the supply. A 60 A supply may well be able to support the actual demand, plus a charge point, but if the sum of the loads for each connected circuit exceeds 60 A then the installation is non-compliant.

I'm sorry, I disagree. I think you will find that the regs allows for actual measured load to determine maximum load. I'll try and find an official link.

[edit]here we go
ENA - Electric Vehicles and Heat Pumps

8. What is Maximum Demand (MD)?
The Maximum Demand of a circuit, property, section of network, or network that considers that all loads associated with that network will not be drawn at the same time.

9. How do I calculate the MD of a premises?
There is guidance in the IET Code of Practice for EV Charging Equipment Installation on supply adequacy (Maximum Demand) assessment. This information is critical to understanding if the EV charge point or Heat Pump can be supported by the network. There are different approaches to determining a site’s MD, including:

  • Use existing information – this is the best approach when there is available data on the specific loads in the house. However, this may not always be the case.
  • Determine loads installed – this approach takes diversity into consideration where appropriate. For this purpose there are different guidelines to assist installers, including:
    • Electrical installation design guide – calculations for electricians and designers
    • On-site guide BS 7671:2018 – IET wiring regulations, 18th Edition
Please contact the IET if you have further questions on the guidance.

Some installers chose to post their customers an internet connected monitoring device which connects to the customer’s internet router and clamps a split Current Transformer (CT) around the supply meter tail. Data is then remotely collected over two weeks at ten minute intervals, before being analysed to arrive at an accurate MD without the need for a site visit.
 
Last edited:
  • Informative
Reactions: Adopado

Glan gluaisne

Supporting Member
Supporting Member
Sep 11, 2019
2,782
2,912
UK
I'm sorry, I disagree. I think you will find that the regs allows for actual measured load. I'll try and find an official link.

I can cut and paste the relevant section from BS7671:2018 if you wish. It probably falls within the "fair use" publication rules, I think.

You can use the actual controlled load as the maximum, for sure, that's how the Garo unit works. Any form of load control that guarantees that the maximum load cannot exceed the rated supply current is allowable. There are other load shedding options, including some smart charge points that sense total load and reduce charge current to stay within limits, and they are allowable.
 
  • Informative
Reactions: Adopado and Roy W.

arg

Supporting Member
Supporting Member
Aug 22, 2012
1,815
1,816
Cambridge, UK
I agree the Garo unit would work, but controlling the load directly (rather than coarsely disconnecting it as the priority unit would do) is preferable, and there are now quite a few chargepoints on the market that support this.

Zappi has it as a standard feature; EO offer it as an optional extra on their units; eVolt have a unit with this as a feature; PodPoint have the capability in their units for commercial installations (I believe it's the same hardware they use for domestic, but I haven't heard of them offering the facility there). All of these will reduce the charging rate, or if necessary shut it down altogether, but by communicating with the car rather than just 'pulling the plug'. Tesla WC has the facility to limit the demand of multiple chargepoints installed together, but not (without a third-party hack) to limit the charging based on other demand in the house.

If trying to assess whether the installation is satisfactory without load control, you can't allow any diversity allowance for the chargepoint itself (both because the regulations say so and because it's blindingly obvious that the chargepoint is likely to remain active continuously at full power for hours at a time). So you are looking at the diversity of the rest of the circuits in the house and seeing whether that plus the chargepoint fits within the existing supply.

The detailed formulae quoted by @Jeremy Harris are just in the On-Site Guide rather than in the regulations themselves, and even the OSG says "The use of other methods of determining maximum demand is not precluded where specified by the installation designer". Personally I wouldn't consider measurement alone (other than over a very long interval) as an effective method, but it may be useful to support a calculation making more optimistic diversity assumptions.

But in reality, a house with 40A supply is exceptionally unlikely to be able to take a 32A chargepoint without load control. A 60A supply might be enough if the load in the rest of the house is small (no showers etc.) A 100A supply (if available) would be ample for most houses (but not all) and a single chargepoint. If you want two chargepoints, you almost certainly want load control unless you happen to have a 100A supply and very little other load.
 
  • Informative
Reactions: Adopado and Roy W.

RX BG69

Member
Oct 8, 2019
16
13
Midlands
I am also in WPD’s region - needing my supply to be upgraded. I have arranged them to visit next week - but they were silent in costs; saying they need to do the survey. I also needs to replace my meter (only rated at 40A) and perhaps the supply cable as well!

However, if you look on the UKPN website (who cover the south-east) they explicitly indicate that they upgrade the fuse to 80 or 100A for free - but I can’t see if they include a cable upgrade for free if required.

I suspect that their regulation requires they provide a free fuse upgrade on older properties, but not including a cable upgrade.

If I have to pay for a cable upgrade I will also consider boosting to a 3-phase supply; recognising that this will be several £k. Alternatively my car is charging fine (albeit slowly at only 10A) off the mains (from a dedicated spur in the garage) which I may continue if I have doubts about staying in the current house.
 
  • Like
Reactions: Roy W.

Glan gluaisne

Supporting Member
Supporting Member
Sep 11, 2019
2,782
2,912
UK
Personally I wouldn't consider measurement alone (other than over a very long interval) as an effective method, but it may be useful to support a calculation making more optimistic diversity assumptions.

Me neither. The issue I'd have is that I could not be confident that the user's pattern of use wouldn't change, or the house might change hands with the new occupier having a very different usage pattern. If the DNO fuse were then to blow, as a result of a sustained overload, the chances are that the DNO might seek recompense from the person that signed the EIC.
 

LEE3

Member
May 16, 2019
319
203
Broxbourne
For general info, we built a self contained annexe on the side of our house last year so this house now has six bedrooms four bathrooms and two kitchens. During my charger installation the electrician turned all the appliances on everywhere to try to measure what the maximum usage could typically be and it was still under 50amps. so it feels like it would need to be quite bizarre circumstances to exceed 60 amps.
 

Glan gluaisne

Supporting Member
Supporting Member
Sep 11, 2019
2,782
2,912
UK
For general info, we built a self contained annexe on the side of our house last year so this house now has six bedrooms four bathrooms and two kitchens. During my charger installation the electrician turned all the appliances on everywhere to try to measure what the maximum usage could typically be and it was still under 50amps. so it feels like it would need to be quite bizarre circumstances to exceed 60 amps.

What if the heating failed and a few electric heaters were plugged in to try and keep the place warm?

This is the sort of thing that can, and does, happen.

The issue is that the installation has to be signed off as OK for any user, not just the current user at the time of the work being done. I've lost count of the number of overheated 13 A outlets I've seen, often in houses with older people, where they've plugged in electric heaters for extra warmth. A look through any of the publications aimed at older people will often show several electric heater suppliers, advertising the ease with which their stuff can just be plugged in for a bit of additional heat (often with some dubious claims as to efficiency, as well!).
 
  • Like
Reactions: Roy W.

Tallboy

Member
Oct 27, 2019
14
4
Sutton Coldfield
I am also in WPD’s region - needing my supply to be upgraded. I have arranged them to visit next week - but they were silent in costs; saying they need to do the survey. I also needs to replace my meter (only rated at 40A) and perhaps the supply cable as well!

However, if you look on the UKPN website (who cover the south-east) they explicitly indicate that they upgrade the fuse to 80 or 100A for free - but I can’t see if they include a cable upgrade for free if required.

I suspect that their regulation requires they provide a free fuse upgrade on older properties, but not including a cable upgrade.

If I have to pay for a cable upgrade I will also consider boosting to a 3-phase supply; recognising that this will be several £k. Alternatively my car is charging fine (albeit slowly at only 10A) off the mains (from a dedicated spur in the garage) which I may continue if I have doubts about staying in the current house.

This is exactly the issue I’m having with them.
Apparently the cable upgrade is chargeable. When the dno guy came round he estimated “£1000 to 1500”.
When the quote came through it was £3700. That was without costs for the digging up of the driveway and having my electrician sort out the wiring and meter. So I’m guessing another few grand for that.
Apparently the reason it’s so much higher than his guess, is because the local council have deemed my road traffic sensitive, so they can only do the work between 7pm and 7am, which seems bizarre as it’s not a bus route or busy road.
My installer sent info about the Zappi and its load limiting function, but apparently that’s not good enough either, despite that being part of the design.
Anyway, my options seem to be limited to using a 3 pin plug, or upgrading my cable, both of which are far from ideal.
I may be able to get a 16amp charger, but even that they’re not guaranteed to approve.

What’s most annoying, is it seems other dnos are happy with the Zappi solution.
 

slonger

Member
Oct 5, 2019
34
9
uk
I am in a similar position. My main fuse is a 60a and have been quoted about £3000 for the cable changing. I have had a quote from an electrician to come and install a Zappi unit with the load management device. He is fully aware of the 60a fuse and doesn't think it will be a problem. At what point might this become a problem for me? if he signs it off will that be the end of it? I live in Yorkshire and under northern power grid.
 

Products we're discussing on TMC...

About Us

Formed in 2006, Tesla Motors Club (TMC) was the first independent online Tesla community. Today it remains the largest and most dynamic community of Tesla enthusiasts. Learn more.

Do you value your experience at TMC? Consider becoming a Supporting Member of Tesla Motors Club. As a thank you for your contribution, you'll get nearly no ads in the Community and Groups sections. Additional perks are available depending on the level of contribution. Please visit the Account Upgrades page for more details.


SUPPORT TMC
Top