EV Charger mounting post - earthing arrangement

Whilst I am not really qualified to give a technical answer, a starting point would be to email (so that their reply is in writing) the Tech Help at Pod Point -  support@pod-point.com and put the question to them.  Also on their web-site is: http://s3-eu-west-1.amazonaws.com/podpoint-website/Earthing-Systems-Information-Sheet-PP-D-200317-2.pdf and https://s3-eu-west-1.amazonaws.com/podpoint-website/PP-D-150179-2-Freestanding-Mount-Install-Guide.pdfwhich may be of some help etc.

Clive

My gut instinct is to bond it to the charger's PE contact DOWNSTREAM of the broken PEN device - i.e. so it's disconnected during a broken PEN event - but remains bonded to the car's metalwork (if plugged in) regardless.

Regs wise that's probably dodgy as extraneous-conductive-parts are meant to be main bonded and it's likely that neither the EV circuit's c.p.c. nor the PE contact are rated for use as a main bonding conductor. (In practice I doubt that the post will have a low enough resistance to Earth to sink much in the way of diverted N currents, so the physics suggest there will never be a problem, but BS 7671 doesn't seem to let us take account of that.)

My 2nd thought is to acknowledge that we rarely bond extraneous-conductive-parts outside buildings (the wording of the reg seems to date from an era when the regs were entitled ‘Regulations for the Electrical Equipment of Buildings’) and IIRC the latest DPC suggested that the wording be adjusted to suggest that main bonding need only apply within buildings. Unless you've got a buried grid or some insulating surface over the ground, bonding a few metallic parts outdoors isn't going to do anything useful in terms of creating an equipotential zone anyway - far from it. So just leave the post unbonded and so let it assume the same potential of it's environment (perhaps other than the EV itself).

That's all presuming it's just an extraneous-conductive-part and not also an exposed-conductive-part (as a metal cased charge point might be).

   - Andy.

Or just TT it.

   - Andy.

Clive and Andy, thanks for your replies, I have now sent an email to Pod Point technical support to ask for their advice.

I see no issue providing you have faith in the open pen device. It opens the earth connection to the car in the event of an open pen.. Metal post to body of car in normal operation could tingle, however. 
There must be millions of bits of class 1 kit  sitting outside buildings that are permanently connected to TN-C-S systems. At least your kit has an additional control measure in terms of the open pen device. 
As you are both designer and contractor , you do right to explore the risks as you would have a duty to consider them under CDM Regs.

I've had a quick skim through of the EV charging equipment COP, 4th edition (2020). It is out of date already. It is a real fudge, with little practical reference to what to do in the OP's situation.

The COP says TT it. But when written, they werent aware of the sudden (?) introduction of the PEN monitoring systems that are becoming prevalent. Well, reading again, it states “although such devices are currently under development, none are commercially available.”

It does have a section about possible future installation, and this part may be the section you need:

5.3.5.4:

“Protective conductors and exposed conductive parts downstream of the open PEN detection device shall not be earthed or bonded to any earthed metalwork or conductors forming part of the PME earthing system that are not protected by the same open PEN detection device….”

“Installers should be extremely careful to avoid accidental , or fortuitous, earthing. This may occur.. when fixing metal clad to earthed metal components .. such as a feeder pillar. …physical separation, or use of insulating materials may be required”

I'd read that as you will have to bond it (is it really required to bond it?) to the incoming supply, and make sure there is no fortuitous link to the outgoing EV supply, or the output after the PEN detector. Or, insulate it from the general mass of earth, and bond it after the PEN detector.

Either way, it isnt very clear what the correct answer is.

But back to the query, does it really need to be bonded? The EV charger is a Class 2, and a Class one device, according to their .pdf instructions. Class 2 presumably the incoming, and 1 the output, TICBW. What chance has the metal post of becoming a danger during normal use?

I'd say very little from the incoming supply, apart from when the unit has been severely damaged. During use, I'd say there was more chance of a damaged outgoing cable rubbing against the pole, and making it live. Again, very unlikely, as the device has it own overcurrent and fault protection, so even if the pole was fortuitously earthed to the ground via its mounting bolts, there would probably be enough current flow to trip the internal RCD.

I'd like to hear more about this situation from people who know more than me!

I'm struggling to imagine any situation when I'd want to bond the post to the supply CPC.

The same earth as the car body perhaps - i.e. the one that is downstream of the PEN fault detector or TT - there I can see an argument that you may make good contact with both at once.

I wonder how well the post is earthed, I think there are 2 cases, one where it is it's  own electrode, and a second where it is it sort of floating 

Are there others ? 

in neither case can  it introduce a dangerous voltage relative to someone standing beside it, nor that connecting it to a PEN would help very much.

I suppose a problem if some odd fault inside the charger that makes the mounting screws live, but there must be better ways of making that incredibly unlikely that do not expose the PEN voltage to touch.

Mike.

The EV charger is a Class 2, and a Class one device, according to their .pdf instructions.

That's a common confusion - it's in a plastic case with no exposed-conductive-parts so as far as that box is concerned it's very much like Class II (i.e. it's a good arrangement to have outside the equipotential zone) - however it still needs a PE connection - not for itself but to pass onto the car (and possibly for its own functional use, but not to provide shock protection for itself) - so it needs to be supplied as if it were Class I. Sort of Class I + II really.

   - Andy.

alanblaby: 
 

I've had a quick skim through of the EV charging equipment COP, 4th edition (2020). It is out of date already.

Chicken and egg. See below.

It is a real fudge, with little practical reference to what to do in the OP's situation.

The CoP is not intended as a set of instructions for every conceivable installation. Similar questions about extraneous-conductive-parts arise with other installations all the time.

The COP says TT it. 

Does it? I agree it says that's an option, but only an option.

 

But when written, they werent aware of the sudden (?) introduction of the PEN monitoring systems that are becoming prevalent. 

Really?

Well, reading again, it states “although such devices are currently under development, none are commercially available.”

That was true. However, as you point out, it's arguably not “out of date” because it contains appropriate advice for the use of open-PEN devices. It's still the case there there is no product standard for these devices. Chicken and egg situation is that if there's no guidance to use open-PEN devices, with there being no product standard, no-one would feel comfy using them … 

It does have a section about possible future installation, and this part may be the section you need:

5.3.5.4:

“Protective conductors and exposed conductive parts downstream of the open PEN detection device shall not be earthed or bonded to any earthed metalwork or conductors forming part of the PME earthing system that are not protected by the same open PEN detection device….”

“Installers should be extremely careful to avoid accidental , or fortuitous, earthing. This may occur.. when fixing metal clad to earthed metal components .. such as a feeder pillar. …physical separation, or use of insulating materials may be required”

That's the relevant guidance for this installation.

I'd read that as you will have to bond it (is it really required to bond it?) to the incoming supply, and make sure there is no fortuitous link to the outgoing EV supply, or the output after the PEN detector. Or, insulate it from the general mass of earth, and bond it after the PEN detector.

That only depends on whether you class the metal post as an extraneous-conductive-part.

Either way, it isnt very clear what the correct answer is.

That's because it hasn't been ascertained whether the post is an extraneous-conductive-part and requires main bonding.

But back to the query, does it really need to be bonded? The EV charger is a Class 2, and a Class one device, according to their .pdf instructions. Class 2 presumably the incoming, and 1 the output, TICBW. What chance has the metal post of becoming a danger during normal use?

I'd say very little from the incoming supply, apart from when the unit has been severely damaged. During use, I'd say there was more chance of a damaged outgoing cable rubbing against the pole, and making it live. Again, very unlikely, as the device has it own overcurrent and fault protection, so even if the pole was fortuitously earthed to the ground via its mounting bolts, there would probably be enough current flow to trip the internal RCD.

I'd like to hear more about this situation from people who know more than me!

I think you've talked yourself towards the likely answer, but it would be for the designer to determine whether this is an extraneous-conductive-part or not. As others have pointed out, similar situations exist all the time.