Do these internally exposed meter tails require mechanical protection?

[drewzh]

Hi,

I was hoping someone with a little more insight might be able to shed some light on a potential issue I have, as I can't seem to find another example online where this specific question that has been answered.

What you can see in the attached photograph is meter tails (single insulated + sheathed), coming in to supply an EV distribution board. It seems from research that most installations are buried with additional conduits for protection, so I'm not sure what the specific rules are around clipped-direct meter tails.

The regs are a little hazy, but should these tails, being situated in a garage workshop, in close proximity to daily tool usage and storage, have further mechanical protection, in the form of metal conduit, or is this perfectly reasonable for a new install?

Many thanks in advance,
Drew

 

[nicebutdim]

Had you asked for the shed to be supplied from the EV board before he started?
It looks like NYY-J as it's got a slight wave to it, it's generally fine to use in domestic environments.

I generally use RCBO's on everything. They are not very expensive so unless there's an operational constraint (like selectivity is important) I can't see how not having it would be acceptable from a risk, cost, effort perspective.
It's true that armoured cables don't need rcd protection but potentially the cable hasn't been installed to requirements like the depth or with tape. An rcd would further limit risk.

Did you ask for no rcd for the EV too?

OP states that sub board circuits are all protected by rcbo. Assuming ads is met on distribution circuit, it would be reasonable enough to ask that it not be rcd protected.

I agree that the cable cleated below appears to be tuff sheath, but took it to be EV charge point supply. Perhaps the OP could clarify which it is.

I seem to have missed the latest image, despite responding to the post in which it was added. Lack of rcd protection on both circuits raises more questions.

 

[drewzh]

OP states that sub board circuits are all protected by rcbo. Assuming ads is met on distribution circuit, it would be reasonable enough to ask that it not be rcd protected.

I agree that the cable cleated below appears to be tuff sheath, but took it to be EV charge point supply. Perhaps the OP could clarify which it is.

I seem to have missed the latest image, despite responding to the post in which it was added. Lack of rcd protection on both circuits raises more questions.

From all of the advice, I had up to the point of installation, not having an RCD on the correctly installed SWA with a correctly bonded armouring was a more accepted approach. Hence why he insisted on adding it, it conflicted with everything I'd been told/read up to that point.

The singles are meter tails taking supply from henley blocks in the meter box. The reason it wasn't added in the meter box itself was due to a lack of space for an 8-way DB in there.

There's no RCD on either circuit - the EV charger is a Tesla Wall Connector and contains built-in Type A RCD with DC current leakage and the shed isn't on RCD for the above reasons. The SWA itself is protected by the armour being bonded and the endpoint is protected with RCBOs.

 

[mainline]

I’d like to see a pic of the other side of the wall along with pics of the inside of the cabinet and DB’s.

It may have been possible to have come in the back of the db, it also may have been possible to have followed the tail run that feeds the main Cu.

What comes to mind here is “too many cooks spoil the broth”.

 

[drewzh]

Had you asked for the shed to be supplied from the EV board before he started?
It looks like NYY-J as it's got a slight wave to it, it's generally fine to use in domestic environments.

I generally use RCBO's on everything. They are not very expensive so unless there's an operational constraint (like selectivity is important) I can't see how not having it would be acceptable from a risk, cost, effort perspective.
It's true that armoured cables don't need rcd protection but potentially the cable hasn't been installed to requirements like the depth or with tape. An rcd would further limit risk.

Did you ask for no rcd for the EV too?

Yes, I asked for the existing shed circuit to also be PEN fault/SPD protected... that's all. I wish I had been more specific about the fact they shouldn't drop my shed feed from 63A to 40A, as I can't find any higher current Garo modules to upgrade it now and need to find another solution.

We have RCBOs on the shed CU. They're not required at the source as the SWA is protected by earthing of the armour. The cable has been installed at the correct depths and with the correct tape also... I know because installed it.

The EV charger has an inbuilt Type-A RCD with DC current leakage, so no RCD is required there.

 

[drewzh]

Do we know for certain that this is SWA and, if so, how is it terminated at the other end? I would have guessed tuff sheath cable due to the compression gland and the likelihood of this cable run on the surface externally.



This may well be why the tails don't enter from the rear.



It's possible that RCD protection is required, although I suspect not. It's most certainly not the case that all buried SWA requires such protection.



Although we'd be splitting hairs, outgoing 63A + 40A circuits would exceed main switch rating. I've no idea whether or not he may have had good reason for reducing the shed supply. Depending on cable size, length of run, installation method, voltage drop... there may be valid reason for doing this, but equally there may not.


The rating will be 40A per pole and this is another possible reason why shed supply has beed reduced to 40A.

It's often difficult to ascertain remotely where problems between customer and installer lie, but I can certainly see why you have reservations about the work. Clear answers from the contractor may have put your mind at ease, but equally clear answers can start alarm bells ringing.

Yes definitely why - I guess in my naivety and lack of understanding of what's correct - I just expected that he'd use the cavity or install it in the skin of the building with conduit or something (I don't mind plastering).

RCD is definitely not required and I knew from research that it's more common than not to earth the armour and leave RCD protection off from the source.

Yes, you are right. I've since decided to bypass the PEN/SPD DB with the shed and feed the hot tub directly on the existing 40A instead of with a new 35m run of 6mm SWA. I always regretted not installing 16mm for the shed (rather than 10mm we were recommended to install) and this negates that issue also. I don't think there was any reason for dropping to 40A other than that's the DB he had with the 40A contactor for PEN fault - I really don't think he gave it that much thought.

Yes, exactly - playing devil's advocate on myself - I could have done more research and worked the circuit out myself, but the EV charger company that did the install were somewhat vague with the technicals until they were here doing the work and it's not always easy to understand the implications of things before-hand if you don't know what it is that could go wrong. In my defence though - I didn't expect them to alter the capabilities of my existing circuit without informing me. I only found out after they had left.

 

[nicebutdim]

Yes, I asked for the existing shed circuit to also be PEN fault/SPD protected... that's all. I wish I had been more specific about the fact they shouldn't drop my shed feed from 63A to 40A, as I can't find any higher current Garo modules to upgrade it now and need to find another solution.

We have RCBOs on the shed CU. They're not required at the source as the SWA is protected by earthing of the armour. The cable has been installed at the correct depths and with the correct tape also... I know because installed it.

The EV charger has an inbuilt Type-A RCD with DC current leakage, so no RCD is required there.

I'm unclear on a few points and uncertain about others.

Is the shed fed by the outgoing cable bellow existing board and has it been extended through to new board?

Is charge point fed by outgoing cable from new board and are you certain that it is swa?

I'm not familiar with tesla charge points, so perhaps someone could clarify if rcd protection can be omitted at source.

Edit: second point since clarified.

 

[drewzh]

I’d like to see a pic of the other side of the wall along with pics of the inside of the cabinet and DB’s.

It may have been possible to have come in the back of the db, it also may have been possible to have followed the tail run that feeds the main Cu.

What comes to mind here is “too many cooks spoil the broth”.

I do think with some extra finesse, he definitely could have hidden the cables.

 

[drewzh]

I'm unclear on a few points and uncertain about others.

Is the shed fed by the outgoing cable bellow existing board and has it been extended through to new board?

Correct

Is charge point fed by outgoing cable from new board and are you certain that it is swa?

Yes and yes, definitely SWA - I saw him hacksawing the armour. There's a concern I have about no metallic gland, so I'm assuming the armouring hasn't been earthed.

I'm not familiar with tesla charge points, so perhaps someone could clarify if rcd protection can be omitted at source.

To my knowledge, it can be omitted as the requirements for a EV charger to be Type B protected are covered by the Type A + DC current leakage protection.

Edit: second point since clarified.

 

[Aaron b]

Correct

Yes and yes, definitely SWA - I saw him hacksawing the armour. There's a concern I have about no metallic gland, so I'm assuming the armouring hasn't been earthed.

To my knowledge, it can be omitted as the requirements for a EV charger to be Type B protected are covered by the Type A + DC current leakage protection.

In most cases the rcd within the charger doesn't meet regs so a external one is also provided. Generally because of the rcd-dd only a type A double pole device can be used instead of the type B, that doesn't mean not required though. It sounds as if you took over the design responsibility on this.

 

[drewzh]

In most cases the rcd within the charger doesn't meet regs so a external one is also provided. Generally because of the rcd-dd only a type A double pole device can be used instead of the type B, that doesn't mean not required though. It sounds as if you took over the design responsibility on this.

This was specified not by myself, but by the EV charger installer (it just happened to conform to what I already knew). From research, it does seem that other installers are also following this approach with the Gen3 Tesla charger. I'm certainly not worried about it.

 

[mainline]

I do think with some extra finesse, he definitely could have hidden the cables.

View attachment 109179
View attachment 109178

The original tails are most defiantly buried and unless they are protected they won’t be compliant.

Did the meter tails originally goto an isolator ?.


The tails from the meter are very short.

I would have liked to have seen either an isolator or Sp+n fused unit there although not really allowed to use the cabinet for consumers gear.

 

[drewzh]

The original tails are most defiantly buried and unless they are protected they won’t be compliant.

Definitely buried and as every other cable in the house is run in a conduit of some kind, I can only assume they're compliant.

Did the meter tails originally goto an isolator ?.

Nope

The tails from the meter are very short.

I would have liked to have seen either an isolator or Sp+n fused unit there although not really allowed to use the cabinet for consumers gear.

I've never really liked the idea of having an isolator outside the house. We have UPS power supplies for our security system, but I still don't like the idea of someone having easy access to switch the power off

 

[mainline]

Definitely buried and as every other cable in the house is run in a conduit of some kind, I can only assume they're compliant.

Nope

I've never really liked the idea of having an isolator outside the house. We have UPS power supplies for our security system, but I still don't like the idea of someone having easy access to switch the power off

Thats no real excuse especially when you have exposed tails buried and clipped up walls.
You assume the tails are in conduit and I also assume that your assuming that the conduit is earthed.

Turning the power off in your case is made simpler by the fact you have no main fuse seals making it easy to pull the fuse.
I can’t believe the meter installer left the tails in blocks without even the thought of using an isolator, which would have been easier to fit and probably cheaper and left the seals intact.

 

[nicebutdim]

Getting back to the issue at hand, I'd rather protect surface clipped tails drilled straight through a wall, than have them buried. Bear in mind these are protected only buy a fuse rated between 60-100A, although I suspect original tails run a short distance up the cavity and aren't buried.

@Aaron b raises a point I'd tried to look into earlier, which is compliance of protective devices installed within tesla gen 3 wall connector. I didn't get to the bottom of whether or not it's compliant with BS7671 and it may well be - I simply can't find info on it.

 

[mainline]

Getting back to the issue at hand, I'd rather protect surface clipped tails drilled straight through a wall, than have them buried. Bear in mind these are protected only buy a fuse rated between 60-100A, although I suspect original tails run a short distance up the cavity and aren't buried.

Trunking or chased with metal plate.