Electric Vehicle charger installation

[stillp]

The BMW i3 to be launched later this year has a fibreglass body.

 

[westie101]

Though

12.3 Roadside and Other Housings Accessible to the Public
Examples are Public Telephones, Pedestrian Crossing Bollards, Ticket Machines etc. Equipment in this type of structure should be Class II (double insulated) or equivalent construction. No mains derived earthing terminal is required, neither is a residual current device needed for earth fault protection

From one of our documents that may cover this situation

 

[ericmark]

Though

12.3 Roadside and Other Housings Accessible to the Public
Examples are Public Telephones, Pedestrian Crossing Bollards, Ticket Machines etc. Equipment in this type of structure should be Class II (double insulated) or equivalent construction. No mains derived earthing terminal is required, neither is a residual current device needed for earth fault protection

From one of our documents that may cover this situation

This seems odd when BS7671 quotes

559.10.3.2 It is recommended that equipment such as lighting arrangements in places such as telephone kiosks. bus shelters and town plans is provided with additional protection by an RCD having the characteristics specified in Regulation 415.1.1.

Although it does say recommended so suppose yes there is no need.

 

[davelx]

In the case of the Vauxhall Ampera/Chevy Volt:

"Re: Vauxhall Ampera

Further to your recent email enquiry I have now received confirmation from our technical experts.

In response to your question, I can confirm that yes, the vehicle body is connected to earth while plugged into the charge point.
.
.
.
Yours sincerely

Angela

My Ampera Agent

Tel: 0800 026 0275

Vauxhall Motors Ltd"

 

[JohnW2]

"In response to your question, I can confirm that yes, the vehicle body is connected to earth while plugged into the charge point."

In terms of some aspects of the discussion we had, I suppose your next question really ought to be "Why?".

Kind Regards, John

 

[davelx]

"In response to your question, I can confirm that yes, the vehicle body is connected to earth while plugged into the charge point."

In terms of some aspects of the discussion we had, I suppose your next question really ought to be "Why?".

Kind Regards, John

I'll give it a try though I would think it's something to do with the fact that the car body provides the -ve/ground connections for the car's internal electrical system and therefore it's not possible to make it double insulated.

 

[JohnW2]

In terms of some aspects of the discussion we had, I suppose your next question really ought to be "Why?".

I'll give it a try

I suppose it might make sense to combine the 'Why?' question with an enquiry about the nature of the charging unit. If it's a metal-cased Class I unit, then I suppose that contact/connection between it's (earthed) case and the car body is probably effectively unavoidable. The question we were really debating is why can't they make it a Class II unit, with the car body not connected to the supply earth.

Kind Regards, John

 

[JohnW2]

... though I would think it's something to do with the fact that the car body provides the -ve/ground connections for the car's internal electrical system and therefore it's not possible to make it double insulated.

You slipped this bit in whilst I was typing! Yes, that's probably the sort of answer you'll get. However, it would certainly be theoretically possible (although not necessarily practicable) to have a double insulated charger unit in which the connections to the car's electrical system (hence body) were totally isolated from the earth of the AC supply.

Kind Regards, John

 

[securespark]

I have often thought about this in relation to 12V vehicles having a mains input, for example campervans.

Bearing in mind the bodywork is the 12V -ve terminal, what happens to the vehicle electrical circuits when a mains earth fault occurs?

 

[JohnW2]

I have often thought about this in relation to 12V vehicles having a mains input, for example campervans. Bearing in mind the bodywork is the 12V -ve terminal, what happens to the vehicle electrical circuits when a mains earth fault occurs?

I can't see why any harm should come to any of the vehicle's electrical circuits, since there would not be any high potential differences within the car - but the car body could, of course, rise to a dangerous level relative to earth (assuming that it was reasonably insulated from earth) until some protective device operated.

Kind Regards, John

 

[bernardgreen]

It is quite simple,

Under fault conditions the Live of the mains could come in contact with the metal body of the vehicle. Protection devices must in this case disconnect the supply.

If the vehicle's exposed metal work is floating ( not connected to anything related to the mains supply ) then it will become Live and remain so as no protective device will operate..

For any device to operate in that case then the exposed metal work of the car MUST be " earthed " when the mains connection is in place. The use of the PME supplied "earth" would be the easiest but would be in contravention of the regulation ( or is it only a recommendation ) about not earthing electrical equipment used in the garden and to use only double insulated tools.

A car is not double isolated. For the mains powered circuitry to be double insulted and transformer isolated from the car's electrical system is possible. But would it remain so for the life of the vehicle ?

 

[JohnW2]

It is quite simple, Under fault conditions the Live of the mains could come in contact with the metal body of the vehicle. Protection devices must in this case disconnect the supply. ... If the vehicle's exposed metal work is floating ( not connected to anything related to the mains supply ) then it will become Live and remain so as no protective device will operate.. For any device to operate in that case then the exposed metal work of the car MUST be " earthed " when the mains connection is in place.

Yes, I think (hope) that we all understand that. I'm a little surprised that you felt the need to write it!

A car is not double isolated. For the mains powered circuitry to be double insulted and transformer isolated from the car's electrical system is possible.

Exactly - and that is precisely the issue that has been discussed in this thread. Given the issues which appear otherwise to arise, particularly with TN-C-S earths (at least, as far as rules/regs are concerned), why do they not do that? As I've implied, is it perhaps down to practical/cost/weight issues relating to the isolation?

But would it remain so for the life of the vehicle ?

Who knows - but that's just a general statement about whether one can ever be sure that any Class II/isolating equipment will always remain 'intact'. Are you suggesting that 'double-insulated' items should be banned, on the grounds that one could not be certain that they would always remain double-insulated?

Kind Regards, John

 

[stillp]

For the mains powered circuitry to be double insulted and transformer isolated from the car's electrical system is possible. But would it remain so for the life of the vehicle ?

I could insult mine more than twice! Not sure if the next owner will though.


Sorry

 

[stillp]

But would it remain so for the life of the vehicle ?

Who knows - but that's just a general statement about whether one can ever be sure that any Class II/isolating equipment will always remain 'intact'. Are you suggesting that 'double-insulated' items should be banned, on the grounds that one could not be certain that they would always remain double-insulated?

Bernard has a fair point, given the poor quality of servicing, which usually gets worse as vehicles age and the owners spend less money. That's not likely to be such a problem with other forms of class II equipment.

 

[bernardgreen]

Yes, I think (hope) that we all understand that. I'm a little surprised that you felt the need to write it!

I am not sure all here do fully understand the different methods of ensuring protective devices will operate when a fault develops.

On the first page of this thread :-

Looking at page 3 first column If an EV cannot be charged inside the building, then the building's PME earth should not be used; So yes TN-S is fine but TN-C-S is not. How one can be certain the supply is TN-S and will never be changed to TN-C-S I don't know. One would need a letter from the DNO saying it was TN-S as the combining may be further back to where one can see.

This effective bans the use ( exporting ) of a PME earth to the vehicle if it outside the equipotential zone of the building.

It mentions that the type of "earth" may be unknown. In which case the only method that will fit all situations is the use of a ground rod to provide a path to ground for the exposed metal of the vehicle while a mains supply is connected to it via a proven double pole earth leakage protection device.

Someone mentioned fibre glass bodies. Provided no one opens the bonnet and touches the engine / motor while charging a shock is less likely though I suspect the metal work of the wheels is not insulated from the chassis / electrical "ground" of the vehicle.