Hi Davey. Is  the SWA cable a three-core type? Should the earth be isolated from the chargers, or is it possible that Black core is being used as the circuit protective conductor and the armouring is being earthed at the distribution board end, considering it is classified as an exposed conductive part? Or is it because you are converting to a TT earthing system at the charger? 
- Andrew

I don't quite follow the 526.8 argument - aren't all the cores enclosed by the EV charger enclosure? 134.1.1 is, as ever, debatable and probably needs a reference to some recognised guidance to make it stick.

I think the stuffing gland approach was suggested by some official guidance some time back for isolating TN c.p.c.s. Personally I don't particularly like the approach as it doesn't make it simple to test the continuity/Zs at the load end of the armour - which you really should do if the armour is being relied upon for ADS for the cable itself (e.g. if the cable is buried or run through an environment where damage is a risk - and if it's not why bother with SWA?). The cable itself should be supported conventionally (e.g. by cleats/P-clips) as required and not rely on the termination of the armour for support. The stuffing gland approach does have the advantage of enuring there are no exposed-conductive-parts of the supply TN system (e.g. the brass gland) within reach of the EV's earthing system.

My preference would be for a brass gland into a plastic enclosure (perhaps the charge point itself, if the enclosure is insulating), covered with a PVC boot to prevent the gland being touched, with the secured in some way if needs be to make sure it can't slip or be accidentally moved to expose the gland. I wouldn't say that was the only option though.

Some might suggest that the boot doesn't have any guaranteed insulting qualities and so if a brass gland is used it should itself be enclosed inside an insulating enclosure to make sure it's not exposed within reach of the EV's earthing system.

Some propitiatory SWA glands have and insulting outer shell, which might be worth consideration for such cases. I have also seen pictures of metal SWA (ZEN?) glands with in-built isolation between armour and enclosure (but I can't say I've ever seen them offered for sale in wholesalers...). and the issue of metal parts of the two systems remaining within reach of each other might still persist even then.

   - Andy.

Davey said:

My colleague and I think this is poor practice and think an isolating gland should have been fitted or the armoured terminated into a plastic enclosure prior to entering the charger. the below regulations are what we believe are contravened. 

It's not unusual to see armoured cables enter through stuffing glands into an internal enclosure or similar, but you need to check the stuffing glands are OK for this.

However 'taping up' is not really insulation, and (with reference to Reg 411.3.1.1, 'Simultaneously accessible exposed-conductive-parts shall be connected to the same earthing system individually, in groups or collectively') what is there to protect electricians carrying out repair/testing from 'simultaneous contact' risk between the two earthing systems?

Cold shrink sleeving is best for this. If the armour (as cpc) is required to be accessible for testing, then something more than 'tape that can be removed' such as insulate the armour with cold-shrink sleeving and if something available for testing is needed, provision of an insulated tail to a suitable 4 mm shrouded test terminal (all insulated), and suitable labelling, would be a better approach ...

So, I would agree, this is a CDM risk that should have been evaluated and something more suitable put in place. This applies even for non-notifiable installations, and non-workplaces, as under CDM designers have a duty to ensure the installation is safe to maintain.

Stuffing glands chosen to grip the SWA adequately, will provide an IP seal where an SWA enters a box, with the outer sheath unbroken.

Done properly, that is perfectly fine, if that is what you wish to achieve.

Is the tape providing site applied insulation to armour on the outside of the box that would be exposed to touch it it were removed, or is it inside an enclosure  that prevents touch ?

The former I'd worry about, the latter less so.  PVC insulation tape is pretty poor as insulation despite the title, and there are better products, as Graham notes, the cold shrink rubber boots are very good, as are the glue lined heat shrinks. Self amalgamiting tape when applied as per the makers instructions cannot be removed by unpicking and as such is as permanent without the use of tools.

The norm for testing Zs is to comb a few strands into some sleeving, and put to a terminal, much as one might terminate split concentric, and then to over sleeve the whole cable in a way that ties in any ends that are cut short. The hazard  of exposure to an 'out of area' cpc potential is comparable to that from an exposed neutral bus bar and there are plenty of those accessible once CU covers are removed and very few dead bodies, it needs to be clear what it is, and that only those skilled in the art will have the lid off.

It may not be beautiful, but  it's not bad.

Mike.

Hi AMK, one of the cores is being used from a O-Pen device, the armouring is being isolated at the point of the charger so that O-pen Earth is kept seperate from the earth of the electrical installation.

My issue is the use of the stuffing gland and that SWA is made off correctly.

Hi AJ, 

I’d be interested to see the official guidance that you mentioned.  
my argument is similar to what you’ve posted, I think making it off into a insulated box would have been the best course of action, however I think in this case they didn’t like the aesthetic  of a box under the charger. 
thr cables are run in ducting then onto tray, so are fixed to the tray. It most probably will never be an issue, but pulling a cable out of a stuffing gland is much easier than a made off SWA. 
you can get these glands, problem is the price tag and availability.

Hil GKenyon, 

 I fully agree it should have been heatshrink used rather than tape and this is where the regulation referring to workmanship comes into play, we are taught that we should follow manufacturers instructions and the regulations, yet poor workmanship still occurs! 

gkenyon said:

However 'taping up' is not really insulation, and (with reference to Reg 411.3.1.1, 'Simultaneously accessible exposed-conductive-parts shall be connected to the same earthing system individually, in groups or collectively') what is there to protect electricians carrying out repair/testing from 'simultaneous contact' risk between the two earthing systems?

That is a very interesting point.

Although I don't think there's any specification as to what insulation should be used. The plastic sheath of an SWA itself isn't rated as electrical insulation but it seems reasonable that we all use it to protect the amour of a cable as it enters a location using a different earthing system. 

Personally I'd rather terminate using an IP rated gland of the plastic variety into a plastic enclosure containing a splice for each live conductor and nothing else. That way there's accessibility for testing and not a lot of opportunity for a fault to either earthing system. But of course I don't have a sheet of paper from the gland manufacturer telling me about it's insulation rating.

Heat shrink certainly offers far more integrity than tape, but whatever solution is still freelancing to some degree or other. In my mind before you can specify insulation you need to be clear what the two thing are which are being insulated from one another, and the particular hazard here isn't an L-E which would operate ADS, but an E[TN-C-S] to E[TT] fault which could rest undetected for a long time.

Keir Stitt said:

That is a very interesting point.

Although I don't think there's any specification as to what insulation should be used. The plastic sheath of an SWA itself isn't rated as electrical insulation but it seems reasonable that we all use it to protect the amour of a cable as it enters a location using a different earthing system. 

Agreed, barrier/enclosure would be OK too ... but importantly, whatever method is employed to protect the maintenance electrician, it needs to be clear what's going on, because it's not like it's a cpc of the installation the electrician is working in/near at the time (effectively).

I

Keir Stitt said:

Heat shrink certainly offers far more integrity than tape, but whatever solution is still freelancing to some degree or other. In my mind before you can specify insulation you need to be clear what the two thing are which are being insulated from one another, and the particular hazard here isn't an L-E which would operate ADS, but an E[TN-C-S] to E[TT] fault which could rest undetected for a long time.

But it is an L-PE shock we're protecting against ... just that the PE in question we're looking at won't have the same local potential rise as the one the electrician is working on.

'gapping' cables between installations is a VERY common occurrence, particularly in the ICT external cabling world.

The only time it gets more involved, is where you have a cable from an HV 'hot site' going somewhere else ... this is more than an LV shock, but you'd need to think about far more than simple insulation in those circumstances. Again, BS 7671 has provisions for the designer to think about this from an overvoltage perspective.

What worries me about the "gapping" situation, is that it seems "going TT" is happening more and more, without thought to the potential consequences.

gkenyon said:

What worries me about the "gapping" situation, is that it seems "going TT" is happening more and more, without thought to the potential consequences.

Yes I was talking through an issue with an Engineer down in Australia the other day. They were perplexed that we have lots of TT. And they were right to be perplexed because there's rarely a compelling argument to TT where supplementary electrodes for the TN[-C]-S won't suffice.

Especially now we've got plenty of options for PEN fault protection if it really is a concern. Generally I'm of the school that having everything at the same potential via main and supplementary bonding which I can be sure of the integrity often by visual inspection trumps separation where to validate safety someone's got to prove the absence of conductivity and hope nothing happens between inspections.