AJJewsbury said:

I’d be interested to see the official guidance that you mentioned.

My memory isn't what it used to be, but I'll try to dig it out...

I'm still digging - I've found one reference in an old GN 8 that refers to "an insulated cable gland" (when supplying a TT'd outbuilding) but that wasn't exactly what I recalled and is open to interpretation anyway (it might mean a cable gland constructed of insulating material, or a brass gland that has insulation applied to/around it, or even a ZEN type gland). I'll post again if I can find what my ageing brain thinks it remembers.

   - Andy.

AJJewsbury said:

I'm still digging - I've found one reference in an old GN 8 that refers to "an insulated cable gland" (when supplying a TT'd outbuilding) but that wasn't exactly what I recalled and is open to interpretation anyway (it might mean a cable gland constructed of insulating material, or a brass gland that has insulation applied to/around it, or even a ZEN type gland). I'll post again if I can find what my ageing brain thinks it remembers.

Yes, GN8 (page 75) does refer to an 'insulated cable gland' (whatever that might be ... I'm sure I've never come across one.

In the railway and infrastructure industries, for this type of interface, it was common to see insulated gland adaptor ("extender" or "gapping") tubes, and appropriate shrink-sleeving insulation, in the following fashion, to prevent simultaneous contact:

I know you have commented on this in the past, "How do I test" later ... the only way would be to put an intermediate tail connector under the sleeving, and bring it out somehow into a suitable insulated terminal.

only way would be to put an intermediate tail connector under the sleeving,

Or to verify in the field where the tail  like that has not actually been done, perhaps a "vampire contact" * with a very sharp probe through/ under the end of the insulation, and if you are lucky a dob of mastic or something similar to fill in the pinprick and conceal the damage.

Plastic stuffing glands do have a lot to recommend them !

Mike

PS * in terms of 'vampires' I've seen the overhead chaps use the tip of a knife blade in a similar way to make a test contact to a single for polarity verification, though to be fair it was a good few years ago, and part of a very temporary hook-up where the underground cable had failed. Rather like the tales of the temporary supply cable coming in through a window or a letterbox, it is more about the duration of the risk being short, vs the risks being acceptable over many years, nor indeed an example of best practice..

Guessing why another electrician has done something will leaving you in whirlwind of three things: was it done with some logic, was it pure laziness, or ignorance to what should have been done, if we give the original installer the benefit of the doubt, their logic could have been, they did not want to use an insulating gland as this would make the gland its self an exposed conductive at the EV charger with the SWA connected to the buildings main earthing system. a problem if the supply earth is PME I am assuming it is based on the use of a OPEN device. 

Meaning in the event of a OPEN fault the charger would be isolated but the gland could still be an accessible earth path from the MET and true earth posing a significant shock risk to anyone that came in Contact with the gland for example any one investigating why the charge point is not working in a PEN fault.

If this was their logic the use of the dome top gland isn't a bad idea but it isn't the right idea.

My opinion would be to use a CW gland at the EV charge point and the insulating gland at the OPEN device this way in normal working circumstances every thing is earthed via the main incoming earth, then in the event a OPEN fault the supply to the EV charger is isolated including the SWA and CW gland as this is now connected to the load side of the OPEN device.

George Hancock said:

My opinion would be to use a CW gland at the EV charge point and the insulating gland at the OPEN device this way in normal working circumstances every thing is earthed via the main incoming earth, then in the event a OPEN fault the supply to the EV charger is isolated including the SWA and CW gland as this is now connected to the load side of the OPEN device.

But in many cases the O-PEN device (or RCD if it's being TTd) is integral to the charge point....

   - Andy.

Hi Andy 

This is true, then other design considerations would need to be made, as this would be outside of the scope of the original question where the charge points are connected to a separate OPEN device in a TN System.