Extranous conductive parts or exposed

[newfutile]

During an EICR I have found an isolator with no cpc present bolted to a large metal post and all the motorized metal car park gate, the fact that the isolator has been moved but the cpcs are not present.

I get a zs from the metalwork of 36 ohms, as the wires pass though I class this as exposed conductive parts.

No rcd is present on the gate circuit.
Would all the rest of the metalwork fixed in the ground count as extranous?

 

[timhoward]

Is is fed by an SWA cable? Just wondering if isolator has been moved whether it once used the armour as a cpc....

 

[buzzlightyear]

No rcd is present on the gate circuit.
Would all the rest of the metalwork fixed in the ground count as extranous?

Where is the feed from.

 

[Lucien Nunes]

Extraneous conductive parts are those liable to introduce a potential usually into a defined equipotential zone. E.g. if the equipotential is created within a building by bonding and earthing to the MET, then an incoming pipe could introduce a different potential if not bonded. But if the conductive part / metal structure is entirely outside, it's not really introducing a potential to anywhere, as it will be at the surrounding equipotential of true earth.

 

[timhoward]

Even though the thread subject said "extraneous", the post said "exposed" which is probably closer to the mark, depending on the details. If there are single insulated conductors inside the metal post, at that point be concerned about the post being an exposed conductive part, and the lack of earthing.
Do you have any pictures?
Obviously the general 'lack of CPC' situation is a separate topic in it's own right.

 

[newfutile]

I am visiting the property again today where I will have more time to investigate and take pictures , it is fed by armoured which then goes inside a metal hollow square post,the isolator is bolted to this.

 

[newfutile]

I'm here again, it's fed from swa to a fcu then more swa into the metal column, inside the metalwork are single insulated wires, no idea what happened to the cpc.

If I connect up a cpc should it just be a cpc, or do I treat it as extranous and run a 10mm bonding conductor to all the metal work?

 

[timhoward]

That's quite an interesting one.

It's your EICR, but in this instance I'd focus on accurately saying what I think is wrong rather than trying to fix it to avoid coding it.
My thoughts -
1 - look at the load that is downstream from the isolator - is there any sign of a CPC, and what does it measure back to the FCU and the MET. If there isn't an adequate CPC from origin to load then that's a C2.
2 - I'd treat the post as steel trunking, it's become part of the electrical installation and has single insulated conductors inside it. I'd argue that is therefore an exposed conductive part and it should be earthed. At the moment the post would become live (save a 37 ohm path to real earth) if something happened to the singles inside it. That's a C2.
3 - I'd be concerned what is going on out of sight inside the post, whether there are any SWA glands (looks unlikely), lack of grommets by the look of it, if there is a CPC connection using the steel armour and how it is made. Unless you have an inspection camera with you that might have to be an FI, though I think I spy a C2 for lack of grommets from the photo, especially as it's not earthed.

For remedial work I'd be more inclined to work out how I could a better job with proper SWA terminations than start fiddling with it. e.g. possibly bring the SWA out nearer the bottom, gland it into a galv conduit box , surface mount galv up the isolator, and go from there.

 

[newfutile]

I work as an electrical inspector for a housing association, i cant give an unsatisfactory EICR except in rare circumstances, therefore it’s usually down to me to fix it and report the work as remedial .

The load appears to be a motor inside the caged area, I suppose I could test to the casing .
The outer of the armour appears to be earthed , I think it can’t be glanded inside the metal post.

I will ensure cpc continuity to the post and circuit end points .

Does the metalwork also count as extraneous ? , im thinking of diverted neutral currents .
however it seems to be TN-S supply as the supply has a SNE SYSTEM label.

Also once a cpc is connected the adjacent gate metalwork could be at a different potential !

 

[Gnasher]

That's quite an interesting one.

It's your EICR, but in this instance I'd focus on accurately saying what I think is wrong rather than trying to fix it to avoid coding it.
My thoughts -
1 - look at the load that is downstream from the isolator - is there any sign of a CPC, and what does it measure back to the FCU and the MET. If there isn't an adequate CPC from origin to load then that's a C2.
2 - I'd treat the post as steel trunking, it's become part of the electrical installation and has single insulated conductors inside it. I'd argue that is therefore an exposed conductive part and it should be earthed. At the moment the post would become live (save a 37 ohm path to real earth) if something happened to the singles inside it. That's a C2.
3 - I'd be concerned what is going on out of sight inside the post, whether there are any SWA glands (looks unlikely), lack of grommets by the look of it, if there is a CPC connection using the steel armour and how it is made. Unless you have an inspection camera with you that might have to be an FI, though I think I spy a C2 for lack of grommets from the photo, especially as it's not earthed.

For remedial work I'd be more inclined to work out how I could a better job with proper SWA terminations than start fiddling with it. e.g. possibly bring the SWA out nearer the bottom, gland it into a galv conduit box , surface mount galv up the isolator, and go from there.

Agree with this.
In addition I would also be checking for negligible resistance between simultaneously accessible parts.

 

[newfutile]

This area is under the flats , the gates secure the car parking area, this also has electrics in it for lighting ,cctv, separator units and so on.
I can’t see that if I reinstate the cpc it’s unlikely that the metalworks will be at negligible resistance on the metalworks , therefore I will have to bond them together .
would this then require a 10mm bonding conductor to the MET?

 

[timhoward]

This area is under the flats , the gates secure the car parking area, this also has electrics in it for lighting ,cctv, separator units and so on.
I can’t see that if I reinstate the cpc it’s unlikely that the metalworks will be at negligible resistance on the metalworks , therefore I will have to bond them together .
would this then require a 10mm bonding conductor to the MET?

I suspect you may be over thinking this one.
Exposed conductive parts need earthing.
Extraneous conductive parts need bonding. To be extraneous they need to be able to introduce a potential from outside the immediate area, and not be part of the electrical system.

Obviously I've not been there. It sounds as though the CPC situation needs sorting, and the terminations in the post need checking/sorting. If there are single insulated conductors in the post, it needs earthing.
Beyond that I'm struggling to see anything that's potentially dangerous.

Once the post is earthed and anything class 1 in terms of lighting, cctv is earthed then any faults should cause ADS before a person can touch any of it. Have you come up with another dangerous scenario that I'm missing?

 

[Gnasher]

This area is under the flats , the gates secure the car parking area, this also has electrics in it for lighting ,cctv, separator units and so on.
I can’t see that if I reinstate the cpc it’s unlikely that the metalworks will be at negligible resistance on the metalworks , therefore I will have to bond them together .
would this then require a 10mm bonding conductor to the MET?

Hi
Remember we are not talking main protective bonding conductors.

Take a look at Table 4.6 in the on site guide.

 

[newfutile]

Part of the gate has a motor , the other parts including a pedestrian gate (selv magnet) is metalwork in concrete , the same with the other metal fencing for lack of a better term,these will be simultaneous touchable with the exposed metalwork which is also partially buried in concrete . Gn8 states that its extraneous if the IR is less than 23 k for 10ma ,currently there is no (RCD) Residual Current Device

 

[Gnasher]

Part of the gate has a motor , the other parts including a pedestrian gate (selv magnet) is metalwork in concrete , the same with the other metal fencing for lack of a better term,these will be simultaneous touchable with the exposed metalwork which is also partially buried in concrete . Gn8 states that its extraneous if the IR is less than 23 k for 10ma ,currently there is no (RCD) Residual Current Device

Take a look at this.

https://www.bing.com/ck/a?!&&p=10fc595ee231e5e7JmltdHM9MTY4MTc3NjAwMCZpZ3VpZD0yM2U0NzFkNy1mZjZmLTYxMWMtM2RiMy02MzIwZmU4ZjYwODYmaW5zaWQ9NTIxMg&ptn=3&hsh=3&fclid=23e471d7-ff6f-611c-3db3-6320fe8f6086&psq=is+it+an+extrainious+conductive+part&u=a1aHR0cHM6Ly9lbGVjdHJpY2FsYXBwcmVudGljZS5jby51ay9ob3ctZG8taS1kZXRlcm1pbmUtYW4tZXh0cmFuZW91cy1jb25kdWN0aXZlLXBhcnQv&ntb=1

What page in Gn8 are looking at?

 

[timhoward]

Part of the gate has a motor , the other parts including a pedestrian gate (selv magnet) is metalwork in concrete , the same with the other metal fencing for lack of a better term,these will be simultaneous touchable with the exposed metalwork which is also partially buried in concrete . Gn8 states that its extraneous if the IR is less than 23 k for 10ma ,currently there is no (RCD) Residual Current Device

Please have a quick look at 411.3.1.2 and note the words "within a building".
If you're standing on concrete on earth, and you touch a post that is sunk into the same concrete/earth, the post isn't extraneous.
I really don't think extraneous conductive parts should be part of your thinking at all here.

The closest clue to this in the regs is maybe in section 714 which explicitly states that metal structures (inc. fences) near an outside lighting installation don't need bonding.

What you might have is simultaneously accessible exposed conductive parts which in certain very specific circumstances (like a bathroom) may require supplementary bonding. But AFAIK only if any of this stuff forms part of a special location and the relevant section 7xx requires that additional protection is in place. (In which case 415.2 would apply, and you then indeed need to satisfy the formula in 415.2.2)
At least, that's my take on it from what you've said.

 

[newfutile]

Perhaps we need to define “in a building“ this is a ground floor car park with all the flats built on top. I will visit this afternoon and take photos.
my main concern at the moment is whether to bond all the metalwork together after i reinstate the cpc to the exposed-conductive-metal post .

 

[Gnasher]

Please have a quick look at 411.3.1.2 and note the words "within a building".
If you're standing on concrete on earth, and you touch a post that is sunk into the same concrete/earth, the post isn't extraneous.
I really don't think extraneous conductive parts should be part of your thinking at all here.

The closest clue to this in the regs is maybe in section 714 which explicitly states that metal structures (inc. fences) near an outside lighting installation don't need bonding.

What you might have is simultaneously accessible exposed conductive parts which in certain very specific circumstances (like a bathroom) may require supplementary bonding. But AFAIK only if any of this stuff forms part of a special location and the relevant section 7xx requires that additional protection is in place. (In which case 415.2 would apply, and you then indeed need to satisfy the formula in 415.2.2)
At least, that's my take on it from what you've said.

Hello timhoward

Hummmmmmm this is getting quite deep now, and interesting, we may never get to the bottom of it but lets give it a go

Had trawl through the book and came up with this.


411.3.1.2 does reference '' Within a Building'' it however doesn't reference outside of the building. 411.3.1.1 Protective earthing, references Simultaneously accessible exposed conductive parts shall be connected to the same earthing system individually, in groups or collectively.

Simultaneously accessible parts. Conductors or conductive parts which can be touched simultaneously by a person
or, in locations specifically intended for them, by livestock.
NOTE: Simultaneously accessible parts may be: live parts, exposed-conductive-parts, extraneous-conductive-parts, protective
conductors or earth electrodes.

415.2.1 Supplementary protective equipotential bonding shall include all simultaneously accessible
exposed conductive parts of fixed equipment and extraneous conductive parts including where practicable the main metallic reinforcement of constructional reinforced concrete. The supplementary protective equipotential bonding system shall be connected to the protective conductors of all equipment including those of socket-outlets.

417.3.1 Simultaneously accessible parts at different potentials shall not be within arm’s reach. A bare live part other than an overhead line shall not be within arm’s reach or within 2.50 m of the following:
An exposed-conductive-part
An extraneous-conductive-part
A bare live part of any other circuit.

418.2.2
Protective bonding conductors shall interconnect every simultaneously accessible exposed conductive-part and extraneous-conductive-part.


714 is a special location covering, Outdoor lighting installations, highway power supplies and street furniture?. Could the reasoning for metal structures (inc. fences) near an outside lighting installation don't need bonding be due to 7614.411.3.4 sating that lighting that is accessible to the public shall have additional protection by an RCD having the characteristics specified in 415.1.1.

 

[LastManOnline]

would this then require a 10mm bonding conductor to the MET?

No it would not. Why ? For the same reason that we don,t run a 10mm bonding conductor to an electric gate or any other metallic accesories that are usually in contact with "true earth".They are not extraneous because they do not introduce a potential into the home that they are supplied from.
However ,running a supplementary bond between the metal post and simultaneousely accessible metalwork makes completes sense.

 

[newfutile]

Would this count as inside the equipotential zone?