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EV electrical supply circuits domestic properties. What should expect to be installed for you

ufo550

Distinguished Member
I trained to be and become a qualified electrician after leaving school. I then chose another career path, until semi retiring and then rejoining the industry. I was a little bit rusty, so did some re-training, mainly inspection & testing for electrical installations, but also the then latest editions of the Wiring Regulations, BS7671.

I've been thinking recently, that when I replace my current car, I might go all electric. So I've been reading through this particular part of the forum. There seems to be a little lack of information, about electrical circuits supplying chargers. So I thought this thread might be informative for members. Perhaps it could be made a sticky Mods? As time moves on, you can guarantee, so will the Regulations & technology.

The world of car charging is not something I did or knew about, so did some research. There's quite a few 'experts' out there, including some manufacturers. However, I quite like this guy John Ward. I'll post some of his vids. They can be a little dull (no offence meant JW :) ) , but he does IMO, explain things clearly and precisely.

The main safety issue with ev charging in domestic (single phase) properties, is the use of TN-C-S supplies PME, where the charging takes place outdoors, or can be expected to take place outdoors. In certain fault conditions, the metal body work of a car, could rise to main voltage. Here's an explanation.

 

ufo550

Distinguished Member
Prior to the release of the BS7671 18th Edition, the section relating to ev charger had a note that said the requirements of this regulation (722.411.4.1) need not be applied..............if none (requirements) is reasonably practicable'. This exception was removed by the 18th.

Amendment 1 released in Spring 2020, made further revisions.

If your still following :) , here's an updated vid from JW. Its a bit longer, but you can skip through the salient bits.

 

IronGiant

Moderator
I'm assuming something similar to video a) happened to me on holiday a few years back. We plugged in the mains lead to the caravan and while kneeling on the ground I happened to touch the galvanised chassis and got a tingling from it. Got out a multimeter and could measure 80V between the chassis and the earth. Plugged into a different socket and the issue went away. I did of course inform the site owner :).
 

ufo550

Distinguished Member
I'm assuming something similar to video a) happened to me on holiday a few years back. We plugged in the mains lead to the caravan and while kneeling on the ground I happened to touch the galvanised chassis and got a tingling from it. Got out a multimeter and could measure 80V between the chassis and the earth. Plugged into a different socket and the issue went away. I did of course inform the site owner :).
That might of been the difference or potential between true Earth and the joint pen conductor, as opposed to the case of broken pen conductor.
 
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noiseboy72

Distinguished Member
There's an article here on touring caravan connections. It shows a couple of earthing options - which would also work for EV charging points as well. It's from 2016, so the new regs might have updated the advice a little.

.
 

ufo550

Distinguished Member
In BS7671 there's different sections for various installations. Caravans/Camping Parks etc come under Section 708, Electric vehicle charging installations appears in Section 722.

Electricity Safety, Quality and Continuity Regulations 2002 (ESQCR) does not allow the use of PME for caravans, whereas it does with EV chargers with certain provisions. Its best to keep to these Sections.

There are some on-line videos, floating about, whereby some sparks have used the Matt:E connection unit (designed for EV), for supplies to outdoor hot tubs (Sec 701). Matt:E have stated their unit has not been designed for such purposes.

Its something that is evolving.
 

ufo550

Distinguished Member
It seems we have to rely on the manufacture and their claims that their devices comply with section 722.

 

the whistler

Active Member
I haven't watched the videos yet, but I will do when I have a few minutes.

My chargepoint (Polar Chargemaster) was installed about 6 or 7 years ago and I think at the time there was nothing in the then current regs about charge points.

Time has moved on and I understand that there the current regs do cover ev charge points. So I'm wondering, if my current installation is safe and does it meet current regs? Or should I really be thinking about upgrading it?

The current installation is basically a three core flexible cable from its own mcb in the consumer unit to a terminal box on the wall, then short cable to the unit.
 

ufo550

Distinguished Member
The main issue is if you supply is PME, and the vehicle being charged outdoors.

In previous wiring regs, there was basically an opt our clause, that allowed its use in a domestic setting. That has been removed under the current regs.

Recent ev charges use the different methods of detecting the loss of a neutral conductor in you supply.

If your in this situation, may well be worth considering upgrading your charger. The vids by John Ward gives a clear explanation, and may help you decide.
 

noiseboy72

Distinguished Member
To be clear, the risk is tiny. Less than 100 reported failures in 10 years over millions of consumers, and to the best of my knowledge, no electrocutions linked back to EV charging.

I would not worry overly about your current charger, and only look to replace it when it becomes life expired or damaged.
 

ufo550

Distinguished Member
To be clear, the risk is tiny. Less than 100 reported failures in 10 years over millions of consumers, and to the best of my knowledge, no electrocutions linked back to EV charging.

I would not worry overly about your current charger, and only look to replace it when it becomes life expired or damaged.
Your incorrect there; I’ve posted you a link before, to the reported loss of a Pen conductor, to such incidents, if you recall.

Which is why when such incidents are reported to a DNO, they react very quickly.

It is not only ev chargers where protective measures need putting in place; caravan sites are not allowed to use pme, for example.

I do wish people would not make light of this issue, hence why the regulations have been amended recently.

As ev chargers become more widespread, then we will be relying on these new technologies to prevent a common danger.
 

noiseboy72

Distinguished Member
Your incorrect there; I’ve posted you a link before, to the reported loss of a Pen conductor, to such incidents, if you recall.

Which is why when such incidents are reported to a DNO, they react very quickly.

It is not only ev chargers where protective measures need putting in place; caravan sites are not allowed to use pme, for example.

I do wish people would not make light of this issue, hence why the regulations have been amended recently.

As ev chargers become more widespread, then we will be relying on these new technologies to prevent a common danger.
PME as opposed to PEN failures (Where the cable fails after the last earthing point) remain extremely low, but I concede, the number of PEN failures should be quoted at around 300 per year - across 29 million plus homes and businesses. That's a failure rate of 0.01%. Failures that led to injury are just 10% of that, so it's fair to say that the chances of being electrocuted due to PEN failure remain very low.

All new systems will fully comply - probably using chargers that have automatic disconnect on Neutral failure, but with such low risk, I wouldn't be looking to replace an existing charger just yet.
 

ufo550

Distinguished Member
PME as opposed to PEN failures (Where the cable fails after the last earthing point) remain extremely low, but I concede, the number of PEN failures should be quoted at around 300 per year - across 29 million plus homes and businesses. That's a failure rate of 0.01%. Failures that led to injury are just 10% of that, so it's fair to say that the chances of being electrocuted due to PEN failure remain very low.

All new systems will fully comply - probably using chargers that have automatic disconnect on Neutral failure, but with such low risk, I wouldn't be looking to replace an existing charger just yet.
I see you've quoted the figures, from the link (page 1) I've previously posted, which I've pasted here again for all to see;

myeneri.com

I don't follow your logic, the failure rate might be low, but you would have a different view of that, if your the one affected.

The effect of an electrical current passing through a human body can have little effect up to being fatal, depending on the circumstances. Bearing in mind cars are now typically parked on driveways or parked in streets, stood in washing water or in the rain sometimes. It exposes not just yourself, but your family and other people, in a fairly high risk situation. The use of pme supplied electricity to a large metal object outside, needs careful consideration. Knowing the risk, I wouldn't wish to expose myself or anyone else to such dangers.

Presumably the risk of electric shock using non protected RCD socket outlets is low; therefore the replacement of non RCD protected sockets, should be argued unnecessary. I don't agree with that argument also, but its one I often heard from money pinching home owners.

The risks of using a PME supply have been consider by changing Wiring Regulations in the last few years. Changes have been made to protect against that risk. I expect they will be more revisions to this particular situation.

@the whistler, unfortunately being an early adopter of technologies, can prove expensive. But what price Health & Safety? Have your installation inspected by a qualified ev charger manufacturer/installer, for a professional opinion.

This whole thing has been poorly thought out, especially with an aging infrastructure.
 

outoftheknow

Moderator
I don't follow your logic, the failure rate might be low, but you would have a different view of that, if your the one affected.
Looking at the risks, somebody with a previously installed charger would be exposed to those risks - the changes as you say were to mitigate those risks. The risks are very small and I am assuming (from 11,000 miles away) that the amendments haven't been applied retrospectively. That would inform the average user that the changes are not considered to address a risk that is unacceptable at the mandatory standards level. If the changes are retrospective to all installations, the risk would be higher.

So users such as @the whistler asking if their installation "remains safe" should note it hasn't become less safe since it was installed. Assuming it was installed to standards accepted to be safe at the time, that is how safe it is now. Risk of electrocution seems to be tiny, but yes the risk is there. If a user wishes to reduce that very small risk to almost zero, have an electrician reinstall the charger (which might mean a new charger.

I can see where you are coming from @ufo550 as a qualified electrician. Of course we should all have installations that meet the latest standards learned from serious incidents over the years. However I personally go along with @noiseboy72 here - as long as the amendments aren't retrospective.

An example here would be RCDs on domestic circuits. We are way behind the UK on these and many houses still have ceramic/wire fuses, let alone MCBs. The risks of fires and electrocutions with those is likely way higher than the risk being discussed here but still very small - none of the changes in AS3000 that covers these things has been retrospectively applied. If you make changes you must meet the standards on the day. You can still swap like for like hotplate type electric hobs without installing the now mandatory switch that breaks all phases for example. Change from gas to induction and you need the switch installed.

Each house owner has sat with the risks for decades and very few will upgrade unless there is a regulatory requirement to, since they haven't been affected. Yes they may be affected by being killed by electrocution - they don't worry about that when it hasn't happened. It is how humans tend to work at the end of the day.
 

noiseboy72

Distinguished Member
I guess the only thing to bear in mind is that the regulations attempt to keep up current lifestyles and usage of the electrical supply.

As an example, my mother bought a 1960s bungalow that had not been upgraded since. The original electrical system comprised of a grand total of 6 single sockets spread around the house, along with an auxiliary electric heater in the bathroom and a signal light fitting in each room. This was all fed from 2 fuses, a 30a for the sockets and heater, and a 6a for the lights.

This would have been considered perfectly acceptable in its day and with the limited number of outlets, the number of connected devices would have been very low, reducing the risk even further. Scroll forward 55 years and the installation is no longer safe. We use far more gadgets around the house and require more sockets, requiring more protection against fire and shock - as well as more circuits to reduce nuisance tripping.

The argument is a little different for EVs, where a loophole in the rules was effectively allowing a less safe form of connection that relied upon an incoming supply remaining correctly connected to be safe. The tiny number of domestic PEN failures makes the sort of fault that could cause the car to become live and unprotected to be on a purely statistical risk basis, too low to be considered. There's little point upgrading the charger or changing the installation. Please bear in mind that just wacking in an earth rod is probably not right solution and if not installed properly could increase the risk of fire in or around the property, as depending upon where the PEN failure occurred, very high currents could flow through the new rod.

As with everything involving dangerous voltages and fuels, it's a balancing act between safety and usability. Filling a car up with petrol is inherently risky and ideally should only be carried out by trained staff well away from anyone else. Of course, this isn't practical, so the risks are mitigated by using highly developed dispensers with multiple protection devices. An electrical charger is really very similar. We are trusting untrained staff to operate equipment containing lethal levels of energy, so all we can do is manage the risk based upon expert advice and real work incident statistics.
 

ufo550

Distinguished Member
Looking at the risks, somebody with a previously installed charger would be exposed to those risks - the changes as you say were to mitigate those risks. The risks are very small and I am assuming (from 11,000 miles away) that the amendments haven't been applied retrospectively. That would inform the average user that the changes are not considered to address a risk that is unacceptable at the mandatory standards level. If the changes are retrospective to all installations, the risk would be higher.

So users such as @the whistler asking if their installation "remains safe" should note it hasn't become less safe since it was installed. Assuming it was installed to standards accepted to be safe at the time, that is how safe it is now. Risk of electrocution seems to be tiny, but yes the risk is there. If a user wishes to reduce that very small risk to almost zero, have an electrician reinstall the charger (which might mean a new charger.

I can see where you are coming from @ufo550 as a qualified electrician. Of course we should all have installations that meet the latest standards learned from serious incidents over the years. However I personally go along with @noiseboy72 here - as long as the amendments aren't retrospective.

An example here would be RCDs on domestic circuits. We are way behind the UK on these and many houses still have ceramic/wire fuses, let alone MCBs. The risks of fires and electrocutions with those is likely way higher than the risk being discussed here but still very small - none of the changes in AS3000 that covers these things has been retrospectively applied. If you make changes you must meet the standards on the day. You can still swap like for like hotplate type electric hobs without installing the now mandatory switch that breaks all phases for example. Change from gas to induction and you need the switch installed.

Each house owner has sat with the risks for decades and very few will upgrade unless there is a regulatory requirement to, since they haven't been affected. Yes they may be affected by being killed by electrocution - they don't worry about that when it hasn't happened. It is how humans tend to work at the end of the day.
Previous additions of BS7671 barred the use of PME supply other than domestic properties, in commercial environments etc. There was an opt out for domestic properties, presumably because the committee who write the regs, had the naive idea that charging would take place inside the equipotenal zone, aka a garage.

One has to realise that PME has not been allowed as a ‘hook up’ on caravan sites for quite some years; should not been allowed for early ev charging methods.

Its also important to understand the danger is not just the incident of lost Pen conductor, but also the possible difference in potential between neutral/earth (pme) and true Earth in the event of a fault.

The 18th Addition draft, was considering an addition of install an earth rod to a pme supply, but was dropped, mainly because of impracticalities, but also likewise picking up ’faults’ from neighbouring properties.
 

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