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]

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?

 

[timhoward]

Would this count as inside the equipotential zone?

That term isn't used in the regs but I take it to mean a location where a different potential could be introduced via an extraneous conductive part.
From your photo's I'd say you aren't in a position where a potential can be introduced from something sunk into the ground when you are stood on that same ground.

I'd work on the basis you have simultaneously available exposed conductive parts.

Reg 410.3.2 suggests that additional protection wouldn't be required notwithstanding special locations or external influences, so doing nothing at all seems to be a valid option.

The next step would be to apply section 415 anyway, and without RCD protection you end up providing supplementary bonding between all of the exposed conductive parts, sized according to 544.2.1

I'm not immediately seeing any mandate in the regs to go a further step and add all accessible metalwork to the bonding. I'll happily be corrected though.

I also can't help wondering if it wouldn't be a lot simpler to sort out the RCD protection for everything in the area. I'd also try and avoid the post staying as an exposed conductive part if at all possible.

 

[LastManOnline]

Would this count as inside the equipotential zone

No it would,nt.And you also can,t turn it in to one.The standard bonding used in a home to achieve an equipotential zone won,t work outside.
Even within the home its only truly achieveable where wooden floors and dry walls are present.Neither of these occur outside.

The best you can achieve, as already mentioned is to bond simultaneousely accessible metalwork.And as Tim mentioned ,providing an rcd would be a huge addition to the level of protection.

Lastly ,as installations go, you could also take great comfort from your TN-S supply.It means you need not worry about the effects of an open PEN and metalwork staying live.If it was TT there could potentially be a significant voltage on the metal under fault conditions ,but this is also a non-issue for you.I would imagine that a fault in a TN-S supply system is the best possible scenario should a fault occur due to the excellent fault return path which should greatly reduce the touch voltage under fault conditions(I may be corrected here by fellow posters as I,m not familiar with the TN-S supply).

 

[newfutile]

I have connected the cpc and bonded all metalwork to each other only , I am waiting for the rcbo .