[GP23]

Hi,

Starting to feel a little out of my depth and grateful for your advice.

I was due to have an EV charger installed for my Model 3 that I hope will be delivered in the coming weeks.

I thought everything would be ok with the install but apparently UKPN has flagged that as my load survey shows total of 105A I may need an upgrade!

I live in a house that was built in 2002. I have an RCD panel and attach a pic of it. Only change at the property was conversion of garage to a play room in 2011 and the electrician at the time added a 32A fuse for the new 'extension ring'. I hope this hasn't caused me a problem?

Total amps as follows from left to right:

B32, B16, B32, B32, B32, B32, B32, B6, B6, B6, B6, B16

Is there anything I can do to avoid the need to install a 3 phase supply?! Is ALM the answer?

Don't want UKPN refusing an install at my property and appreciate any advice you can give.

Thanks

 

[cDy]

1. What is the DNO (network operators) fuse on the incoming supply? Is it 100A or less?
2. You can always have a Zappi charger with a sensor on the incoming supply. The Zappi will then limit what the car takes so the DNO fuse is not overloaded. There are other EVSE that support this capability.

 

[GP23]

Thanks for quick reply!

DNO fuse is 100A.

Great to know re: the Zappi.

Would you say any other charger is likely to cause me a problem then? Really didn't think my house was a break from the norm.

 

[dk6780]

What are they talking about? It's not a simple matter of summing the RCBO ratings, but instead looking at the typical loads. Do you have electric heating (presumably not as that is only a 16A circuit)? Electric showers and ovens? And something else like an electrically heated swimming pool?

as @cDy says, did UKPN say what your current incomer fuse is?

Lots of charge point suppliers have the ability to cap the maximum load, but I can't see why it is necessary yet.

 

[cDy]

You can use 'diversity' on the existing loads. That is, it is highly unlikely that they will all be on at once, so you can work out a lower number to use. Your electrician can do the calcs for you, or do a search on diversity for guidance. You can't use diversity on the EVSE, so the question is whether you can run the house on 68A. The likely answer is 'yes' you can, unless you have too many high current loads, as @dk6780 suggests.

 

[davesul]

This document illustrates the 'load curtailment' feature of certain EVSEs and indicates the possible adjustment settings for limiting the the current drawn from the supply tails (when the EVSE is operating).

https://myenergi.de/wp-content/uploads/2020/06/Technical-bulletin_grid-limit-March-2020.pdf

 

[GP23]

What are they talking about? It's not a simple matter of summing the RCBO ratings, but instead looking at the typical loads. Do you have electric heating (presumably not as that is only a 16A circuit)? Electric showers and ovens? And something else like an electrically heated swimming pool?

as @cDy says, did UKPN say what your current incomer fuse is?

Lots of charge point suppliers have the ability to cap the maximum load, but I can't see why it is necessary yet.

This is why I got confused, response from UKPN to them completing the EV & HP application was:

You have advised on your application form that your maximum demand exceed 100amps. Therefore in order to continue with this installation, you will need to upgrade your current electricity service at the above site address.

Their application calculated total load as 105A.

I do not have electric heating, no electric shower. Two ovens, one is small and never use both at the same time.

No heated swimming pool! Overall, low load, but I'm concerned they've cause an issue for me with UKPN who might flag this for any future install. In order to try and circumvent, I've got a free survey by UKPN this Thursday and hoping they will confirm under no circumstances do I need a phase 3 supply to have an EV charger!!!

 

[dk6780]

That's a sensible approach. Sometimes they calculate the demand based on the floor area of the house or the number of rooms and assume that you a have crammed as many people in as possible.

What rating did you declare the ovens as? I'd be surprised if they are more than 16A despite the 32A RCBOs.

 

[cDy]

Who's doing the EVSE install? They should be liaising with the DNO and there should be no problem. Also, ask them to explain the earthing arrangements they are going to use - requirements changed in the latest (18th) edition of the regulations. They could install an earth rod or, alternatively, an EVSE (or additional box) able to totally isolate the EVSE if a fault occurs.

 

[GP23]

Who's doing the EVSE install? They should be liaising with the DNO and there should be no problem. Also, ask them to explain the earthing arrangements they are going to use - requirements changed in the latest (18th) edition of the regulations. They could install an earth rod or, alternatively, an EVSE (or additional box) able to totally isolate the EVSE if a fault occurs.

They said they had liaised with the DNO who suggested they should install an ALM device...for some reason installer has calculated total usage as 105A hence why it was flagged.

Earth arrangement - installation of Matt:e box as an alternative to the earth rod.

I am keen to have everything installed on the side wall of my house (where the elec meter is) as space is quite tight in the cupboard where the RCD panel is. Apparently they can use an IP rated box alongside the meter and bypass the need to install anything inside the home? Can this be done with any of the EV units including the Tesla charger?

Sorry for the number of questions but as you can tell I am no expert!

 

[GP23]

That's a sensible approach. Sometimes they calculate the demand based on the floor area of the house or the number of rooms and assume that you a have crammed as many people in as possible.

What rating did you declare the ovens as? I'd be surprised if they are more than 16A despite the 32A RCBOs.

All I was asked at the time was to total up all the fuses, so I would have provided 32A for those.

 

[dk6780]

All I was asked at the time was to total up all the fuses, so I would have provided 32A for those.

who suggested they should install an ALM device

Earth arrangement - installation of Matt:e box as an alternative to the earth rod.

So you have had an installer out, and they are trying to fit some form of current limiting device in addition to Earth rod alternative. I think that you need a second opinion, and adding all of the "fuses" up is not the correct approach to calculating load. What type of charge point did they suggest?

Incidentally, FWIW the total of my RCBOs is greater than that with the same 100A incomer fuse and I have no problems running 2 x 32A charge points + the immersions during plunge pricing episodes on Agile - mainly because I'm not using other electrical items at the same time.

 

[GP23]

So you have had an installer out, and they are trying to fit some form of current limiting device in addition to Earth rod alternative. I think that you need a second opinion, and adding all of the "fuses" up is not the correct approach to calculating load. What type of charge point did they suggest?

Incidentally, FWIW the total of my RCBOs is greater than that with the same 100A incomer fuse and I have no problems running 2 x 32A charge points + the immersions during plunge pricing episodes on Agile - mainly because I'm not using other electrical items at the same time.

No one has visited my property. They seem to have calculated load based on the info I provided them and nothing more.

The ALM has only been suggested now (by UKPN to the installer) as the alternative to avoiding phase 3 supply!

Definitely getting a second opinion. Suggested charge point was an EO.

Thanks for reassuring me - was convinced there was nothing out of the ordinary with my circuitry and loading!

 

[dk6780]

I suspect that this is what they are trying to justify selling you.

EO Active Load Management Unit

It does the same job as @cDy describes with the Zappi and @davesul links to more generally.

If you want to be able to come home and plug two EVs in whilst running both the ovens, immersion heater and everything else electrical in the house at the same time it might be needed, but with just a single EV and if you use off-peak charging then you don't need it.

 

[GP23]

Thank you so much.

 

[dk6780]

And breath again!

When things have calmed down, discuss with your second opinion person the difference between an Earth rod and the Matt:e device in the event of a failure of the PNE Earth.

I am keen to have everything installed on the side wall of my house (where the elec meter is) as space is quite tight in the cupboard where the RCD panel is. Apparently they can use an IP rated box alongside the meter and bypass the need to install anything inside the home? Can this be done with any of the EV units including the Tesla charger?

That's much the most sensible approach anyway. It can be done with any charge point including Tesla. The only possible issue with the Tesla charge point is that it doesn't qualify for the OLEV grant - but that's of debatable value.

 

[cDy]

I've not checked the technical details, but I believe that Zappi is also supposed to provide the necessary supply isolation to meet the latest amendments to the regs, without the need for a separate Matt:2 box or an earth rod.

I also have RCBOs far exceeding 100A and run a single (non-smart) 32A EVSE, electric ovens and hob, and two electric showers without any problems at all.

 

[dk6780]

I've not checked the technical details, but I believe that Zappi is also supposed to provide the necessary supply isolation to meet the latest amendments to the regs, without the need for a separate Matt:2 box or an earth rod.

It does. Some others also do, such as the ChargedEV Smart+.

 

[SHL-Kelso]

I’ve got a 100A supply, and if you only used the MCB/RCBO ratings in my consumer units then my supply fuse would have blown long ago! I’ve an all-electric house, with ground source heat pump for main house heating and hot water, separate electric UFH, shower, and hot water heater in a garage granny annexe, and 2x32A EV chargers (both installed with OLEV funding). Only the second charge point t installation fell foul of the standard load calculations including allowable diversity, hence I have a Zappi with CTs to provide load management control on the 2nd chargepoint (the first unit was a dumb 32A Rolec).

I also have extensive monitoring so know that even without the load management I would not overload my supply, but the DNO needed a foolproof solution (quite rightly) to ensure there is zero chance the supply gets overloaded. The hardest part was getting the DNO to understand the nature of the issue so that we could get their approval - this took 3 months (although most of that was wasted time, and the decision was made/agreed within 2 days once we were able to speak directly to the department concerned). However, without the DNO approval my OLEV-funded installation could not take place.

 

[GP23]

Thanks everyone, so very helpful and reassuring.