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hiya chaps


I did a City and Guilds course, practical assessment and exam for the CG2919 on Monday and Tuesday, we were told about the difficulties with ensuring the safety of the charging equipment especially regarding the earthing in domestic properties, lots of discussions were about using the isolating transformer instead of converting the existing property to a TT system.


My question is which isolating transformers do you EV guys use typically looking at supplying a 7 Kw charging unit, where do you get them from and what is the cost of them.


Regards


Lee
 
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freddo

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Plenty of companies sell isolation transformers, for 7KW it will be large, heavy and expensive.
 
 
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Bill01803


The issue isn’t conversion of the clients property to a TT system, if there is any class 1 light outside fittings or bonded pipes to gas or water within 10 metres of the charging point you have the risk of dangerous touch voltages under earth fault (possibly from neighbours property etc) it’s part of the risk assessment you have to carry out prior to installation.

EV installation not straight forward external influences play a big part of installation, if you change the property from a PME to TT there’s always a risk of another electrician who doesn’t know the legislation on EV installation puts the PME connection back.

Also some ground conditions you would struggle to get the earth potential acceptable for the EV installation, hence why in the installation it’s easier and straight forward to install an isolating transformer.


Lee
 
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bill01803

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“Puts the PME back”

I don’t think you should be concerned about what another electrician may do in the future, as long as it is correct when you have completed your work.
 
D

Deleted member 26818

I was not aware the requirement is to change an existing installation from PME to TT?
I thought the requirement is to make just the EV charger TT?
 

bill01803

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I think he is concerned about touch voltage between the class 1 fittings so considering TTing the whole installation
 
I can understand not wanting to get involved with checking and changing electrical instalations and then being responsible for that instalation to some degree. but it;s not that easy with a 7kw load involved, that's not exactly a trivial load, and any transformer of 7kw capacity will be large and expensive, so there is NO easy way out. I say forget the trasformer idea ! it's just not practicle.
 

DPG

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OP, could you clarify - were you meaning make the whole house electrical system TT?
 
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I can understand not wanting to get involved with checking and changing electrical instalations and then being responsible for that instalation to some degree. but it;s not that easy with a 7kw load involved, that's not exactly a trivial load, and any transformer of 7kw capacity will be large and expensive, so there is NO easy way out. I say forget the trasformer idea ! it's just not practicle.


Check out the wiring regulations on EV charging it’s the only sensible way to go with PME unless the DNO can guarantee that there will never be a damaged cable to the neutral you need to carry out a risk assessment on the installation, I did my City and Guilds 2919-10 on Monday and Tuesday this week and going through the regs the only solution is to go down the isolating transformer (been told there’s a small unit that does 7Kw that fits a din rail unit ( not in a CU) that’s around the £200 +Vat price range just trying to find who sells it)
 

DPG

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I'd like to see a 7000 watt transformer that would mount on a DIN rail. Not saying it's impossible but can't imagine it
 
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F9C618BD-7288-4806-B5F5-0394DF028A14.jpeg 7ED0D050-4A4C-4C15-A00C-3CA3DF649087.jpeg C9098D0C-32C7-4A48-A931-532961CC5E59.jpeg 0F0D23E9-ABBC-427B-A35F-AE8527ED9F49.jpeg 24975458-17A1-478D-84A3-B7F8C57B7327.jpeg 5A0FF3B0-E82D-4A28-B00E-8A0055AFEF69.jpeg 7ED0D050-4A4C-4C15-A00C-3CA3DF649087.jpeg C9098D0C-32C7-4A48-A931-532961CC5E59.jpeg
 
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Sorry they’re not in order

If there’s a class 1 light or bonded pipe within 10 metres of the charging point the charging point cannot be on a separate earthing system to the property or the neighbours property
 

Lucien Nunes

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I've never installed a charging point and unfamiliar with accepted practice, but I can say with certainty that no 7kVA wirewound transformer ever mounted on a DIN rail. It will be in the order of 50-60kg and the size of a case of wine unenclosed. This is due to physical limitations of the copper and steel, and until someone invents a revolutionary material with better properties, it won't change much. It is possible to make a smaller, lighter switched mode converter, although not for a few hundred pounds.

But, surely the sensible approach is a device that disconnects the supply in the event of the PME earth exceeeding 70V to local mass of earth, as detailed in 722.411.4.1 option (iii). Put in two small spikes nearby (resistance need not be very low, and the two would allow for automatic monitoring of resistance), see the green light come on and the job is done. It's basically an improved version of a VOELCB used for a more suitable purpose, obviously with a bit of engineering to make it reliable enough to switch the PE as well as the live conductors.

I have to wonder why the charging point makers don't offer an integral solution. 722.411.4.1 option (iii) even suggests the voltage detection device could be included in the charging equipment. The convenience of being able to install one product to any supply without further complications would surely be attractive in spite of increased cost.
 
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mattg4321

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Can't see how its possible to fit an EV charger in most cases then. Back to petrol we go!

Sorry LeeBut a 7kw isolating transformer will be around £1000 and pretty large. Not an option.

Is your book saying a EV charger electrode can't be within 10m of a buried metallic bonded pipe, outside light, outside socket etc etc. Doesn't sound like this is possible in most cases where the charger would be mounted to an outside wall of a dwelling.

Anyone else that's done the course? Thinking of doing it soon, but if this is the case!
 
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  • #20
Can't see how its possible to fit an EV charger in most cases then. Back to petrol we go!

Sorry LeeBut a 7kw isolating transformer will be around £1000 and pretty large. Not an option.

Is your book saying a EV charger electrode can't be within 10m of a buried metallic bonded pipe, outside light, outside socket etc etc. Doesn't sound like this is possible in most cases where the charger would be mounted to an outside wall of a dwelling.

Anyone else that's done the course? Thinking of doing it soon, but if this is the case!


Yes it does, this is the reason why they say you should go down the isolating transformer route because if you live in a new estate house close together you cannot guarantee safe earthing if you convert property to TT. system
 
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I've never installed a charging point and unfamiliar with accepted practice, but I can say with certainty that no 7kVA wirewound transformer ever mounted on a DIN rail. It will be in the order of 50-60kg and the size of a case of wine unenclosed. This is due to physical limitations of the copper and steel, and until someone invents a revolutionary material with better properties, it won't change much. It is possible to make a smaller, lighter switched mode converter, although not for a few hundred pounds.

But, surely the sensible approach is a device that disconnects the supply in the event of the PME earth exceeeding 70V to local mass of earth, as detailed in 722.411.4.1 option (iii). Put in two small spikes nearby (resistance need not be very low, and the two would allow for automatic monitoring of resistance), see the green light come on and the job is done. It's basically an improved version of a VOELCB used for a more suitable purpose, obviously with a bit of engineering to make it reliable enough to switch the PE as well as the live conductors.

I have to wonder why the charging point makers don't offer an integral solution. 722.411.4.1 option (iii) even suggests the voltage detection device could be included in the charging equipment. The convenience of being able to install one product to any supply without further complications would surely be attractive in spite of increased cost.
We asked the same questions as to why the manufacturers such as Rolec dont install them, I’ve heard another manufacturer does include the device but I cant find who does it
 
The guidance I received on acceptable TT Ra test results where the charge point was 32A and supplementary earth rod was to be installed on the MET of a TNS or TN-C-S was an RA less than 5Ω was considered stable where as it’s less than 200Ω for whole house TT rod. The other issue is this 10 meter zone. When charging leads can be 7.5Mtrs in length and the charging ports on the cars are not all in 1 standard location. So it is possible for the vehicle to be charged in different locations on the drive plus add the vehicle length, difference in plug location you could have an earthed metallic pipe or fitting that is not reachable with say a Nissan Leaf but you chuck a Tesla on the drive it suddenly becomes very touchable.
 

Paignton pete

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Good news leebut the voltage potential difference device that wasn’t invented when the ev charge code came out is now in production.

There was a recent threat on this issue and more information is on there.

I will try to locate the thread.
Post automatically merged:

Have a look at the thread “Updates to 722”.

Not the thread I was looking for but it’s relevant
Post automatically merged:

“EV Charger Installation - Cabling Query?” This was the thread I was originally looking for.
 
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Simon47

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So you install an isolating transformer, the trailing cable gets damaged and the "L" gets earthed. The car is now at 240V until someone touches it and the ONLY protection is the load-side RCD. Or put another way, the only protection against shock in that case is a device that's known to fail from time to time - I think we've all, or at least a lot of us, come across RCDs that don't trip when tested.
You also need active monitoring to ensure that (eg) insulation breakdown in the transformer or wiring doesn't make the vehicle "hard" to 240V (or some subset of it) with zero protection other than any upstream RCD.
Might as well save the cost (and bulk) of the transformer and just have active monitoring of CPC vs local ground voltage as already mentioned.
 

davesparks

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So you install an isolating transformer, the trailing cable gets damaged and the "L" gets earthed. The car is now at 240V until someone touches it and the ONLY protection is the load-side RCD.
The car is only at 240V relative to the other pole of the transformer output, it will not present a shock hazard unless the person is in contact with the other pole of the output at the time they touch the car.
 
Most residential EV chargers are converted to TT. However a new generation of chargers are being introduced which monitor the PME supply and disconnect. Do EV chargers need earth rods - https://www.efixx.co.uk/Articles/next-generation-ev-charge-points-don-t-need-earth-rods
 

Gavin John Hyde

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There is a good source of devices to allow you to use chargers on a pme system. Cost around £130 per unit pdfs below.
Havent used one yet as i opt for the pod point solo or go down a tt set up.
 

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Amp David

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After completing this very course, it made my mind up for me, not to bother getting involved with EV. Its not a good business decision for a one man band like myself.

More regs, more paper work and less time to spend away from working!
 

Paignton pete

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After completing this very course, it made my mind up for me, not to bother getting involved with EV. Its not a good business decision for a one man band like myself.

More regs, more paper work and less time to spend away from working!
Absolute ditto.

I did the course and came to exactly the same conclusion.
 
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  • #32
OP, could you clarify - were you meaning make the whole house electrical system TT?
Yes the wiring regulations states you cannot install a car charging unit onto a PME supplied installation if you are to install the car charger as a TT system on it’s own there cannot be any metal conductive parts or class 1 external light fitting within a 10 metre area of the charging point which on a new housing estate would be impossible to achieve
 
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  • #33
I’ve done a load more research on these EV charging points and I’ve now found out that a company called Zappi is producing a charging point that doesn’t require an earth rod the model you need to check out is the Zappi V2
 

Midwest

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I’ve done a load more research on these EV charging points and I’ve now found out that a company called Zappi is producing a charging point that doesn’t require an earth rod the model you need to check out is the Zappi V2
There’s another one, probably more now. See post 28.
 

richy3333

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Theres about half a dozen companies making EV chargers that dont require TT'ing.Zappi's are on an 18 week order time at the moment.

@leebut you said you cant install a charger on a PME system, but I'm sure you are aware that statement isn't correct if you did the course?
 
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Theres about half a dozen companies making EV chargers that dont require TT'ing.Zappi's are on an 18 week order time at the moment.

@leebut you said you cant install a charger on a PME system, but I'm sure you are aware that statement isn't correct if you did the course?
I did the course, the regs say you can’t install on a PME supply due to the risk the earth might fail
 

davesparks

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I did the course, the regs say you can’t install on a PME supply due to the risk the earth might fail
But there isn't a high risk of the earth failing, there is a high risk if the supply neutral were to fail.
These two things are very different.
 
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  • #38
But there isn't a high risk of the earth failing, there is a high risk if the supply neutral were to fail.
These two things are very different.
On PME if the neutral cable is to get damaged the earth also fails as it’s the same conductor!!

hence the IET’s concern!!
 

davesparks

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On PME if the neutral cable is to get damaged the earth also fails as it’s the same conductor!!

hence the IET’s concern!!
Yes, but that doesn't mean there is a high risk of it failing, it means there is a high risk if it fails.
The risk of it failing is low,
 
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Yes, but that doesn't mean there is a high risk of it failing, it means there is a high risk if it fails.
The risk of it failing is low,
I’m not the one making the Regs or arguing over them I’m just trying to comply with them, if the Regs say we can’t install an EV charging point on a PME we don’t do it, otherwise what happens if someone gets killed through your neglect.

I don’t like the idea that they say you convert the home to a TT system from PME, what happens when another electrician comes along again who doesn’t know the Regs reconnects to the PME and someone dies how do YOU prove you did what you did correctly and someone else has changed it, because he’s not going to admit the changes if he’s facing a manslaughter charge!!
 

richy3333

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I did the course, the regs say you can’t install on a PME supply due to the risk the earth might fail
No they dont and it was that I was trying to tease out of you. If the charger and charging is to be indoors then PME can be used. If you ddi the course you'll have the IET GN on the matter - see page 39. Your comment is correct (sort of) for outdoor charging but you did not reference PME and outdoor charging.
 
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No they dont and it was that I was trying to tease out of you. If the charger and charging is to be indoors then PME can be used. If you ddi the course you'll have the IET GN on the matter - see page 39. Your comment is correct (sort of) for outdoor charging but you did not reference PME and outdoor charging.
99% of installations are going to be external installations where you can’t use PME, Yes I do have the guidance notes, if you look at my post #15 I’ve photographed and highlighted the pages from my Guidance on installation of EV AND YES I HAVE READ ABOUT INTERNAL INSTALLATIONS.

so does your comments mean you would install an EV charger in someone’s porch at the front of their house and the car be outside and that’s acceptable NO!!

the vehicle is to be charged in the garage with the charging point in the same garage, now be honest is that your normal installation again NO!!
Post automatically merged:

99% of installations are going to be external installations where you can’t use PME, Yes I do have the guidance notes, if you look at my post #15 I’ve photographed and highlighted the pages from my Guidance on installation of EV AND YES I HAVE READ ABOUT INTERNAL INSTALLATIONS.

so does your comments mean you would install an EV charger in someone’s porch at the front of their house and the car be outside and that’s acceptable NO!!

the vehicle is to be charged in the garage with the charging point in the same garage, now be honest is that your normal installation again NO!!
5291BAE2-5211-41D8-8F8E-F26F5EF11B03.jpeg
Post automatically merged:

No they dont and it was that I was trying to tease out of you. If the charger and charging is to be indoors then PME can be used. If you ddi the course you'll have the IET GN on the matter - see page 39. Your comment is correct (sort of) for outdoor charging but you did not reference PME and outdoor charging.
FA0F3C29-225B-44EE-A561-F14A8D28FB80.jpeg
And there you go that’s my proof I did my 2919 course
 

davesparks

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99% of installations are going to be external installations where you can’t use PME, Yes I do have the guidance notes, if you look at my post #15 I’ve photographed and highlighted the pages from my Guidance on installation of EV AND YES I HAVE READ ABOUT INTERNAL INSTALLATIONS.
Your post #15 does not support your statement that PME is not allowed, it clearly says that a PME connection can be used when certain requirements are met.

So PME can be used subject to certain requirements,
 

AJshep

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We are not allowed to quote regulations anymore but 722.411.4.1
Basically says a PME earthing facility shall not be used unless one of the following methods are used......
The third indent (iii) is the one that the Zappi charger and others appear to have complied with which in a nut shell disconnects the Live conductors as well as CPC from the charging point in the event of a PEN fault.

I haven't done the course, so happy to be corrected.
 
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Your post #15 does not support your statement that PME is not allowed, it clearly says that a PME connection can be used when certain requirements are met.

So PME can be used subject to certain requirements,
My point was I was being accused of NOT doing the course or having the Guidance notes book on EV charging so I flicked back to see the post where I had copied in my Guidance notes that was all!!
 

richy3333

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No need to get worked up. And I don’t think accused you of anything. I was trying to highlight your original statement was not correct. In your defence you’ve now added lots of caveats to justify it.

apologies if I upset your sensitivity.
 
Can some one expalin to me then if the PEN connection is lost supplier side how does not all the bonded conductive parts become live? Why such focus on the EV charger point?
 
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Can some one expalin to me then if the PEN connection is lost supplier side how does not all the bonded conductive parts become live? Why such focus on the EV charger point?
The only reason for highlighting the EV issue on a PEN conductor loss, is the car charging is exterior to the property and is a 7Kw load that’s at full load for the duration of charging process
 

Risteard

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Can some one expalin to me then if the PEN connection is lost supplier side how does not all the bonded conductive parts become live? Why such focus on the EV charger point?
The bonded parts would be within the equipotential zone though, so with adequate bonding hopefully the touch voltages won't rise too much and give rise to the risk of electric shock.

However outside a person charging an EV is likely to be in simultaneous contact with true Earth, and with the MET at a dangerous potential owing to the PEN fault.
 

Midwest

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The other thing to consider, is a car is just sat there in such circumstances, with four feet bits of fat rubber.
 
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