SWA to T&E. Moving a plastic junction box. Gland and banjo question

[flameport]

what would you say if it were a 2-core cable which was 'mechanically protected' (but not by earthed metal)

Not going to happen.

411.3.1.1
A circuit protective conductor shall be run to and terminated at each point in wiring and at each accessory except a
lampholder having no exposed-conductive-parts and suspended from such a point.

A submain is not a lampholder.
CPC is required regardless of whether it is connected at the load or not.
If the SWA isn't connected to a suitable gland, the CPC cannot be properly terminated.

 

[JohnW2]

Not going to happen.
411.3.1.1
A circuit protective conductor shall be run to and terminated at each point in wiring and at each accessory except a
lampholder having no exposed-conductive-parts and suspended from such a point.

I was rather expecting that one, and nearly 'pre-empted' it, but gambled (incorrectly) that no-one would produce it

The relevant CPC which has to be run to every point/accessory in the (TTd) outhouse is surely the CPC which is connected to the local (TT) earth system? You obviously (hopefully!) aren't suggesting that the (not used in outhouse) TN-C-S earth has to be run to every point/accessory in the TTd environment?

Kind Regards, John

 

[SUNRAY]

Not going to happen.

411.3.1.1
A circuit protective conductor shall be run to and terminated at each point in wiring and at each accessory except a
lampholder having no exposed-conductive-parts and suspended from such a point.

A submain is not a lampholder.
CPC is required regardless of whether it is connected at the load or not.
If the SWA isn't connected to a suitable gland, the CPC cannot be properly terminated.

Are you not getting a bit confused here?
Surely the CPC mentioned in that has to be the relevant CPC for the circuit in question.

My understanding of that reg is the CPC that would end up at say a socket or other outlet point. is the point to test.

In this example of a TT system fed by 2 wires on overhead poles the circuit terminating at the 13A socket will I assume refer to the point 'Z' as the CPC.
Likewise at the CU the earth bar or point Y.

So on that basis why would you test to point 'X' when it is not relevant to the installation.

Or am I missing something fundamental?

 

[flameport]

A submain is a separate circuit, and requires a CPC and testing just like any other.
It would be tested using X as the CPC and recorded on the certificate as one circuit.

The other circuit(s) from the consumer unit would be tested using Y as the CPC, and they would be recorded on the certificate as separate circuit(s).

TT supplies on overhead poles are DNO items and not covered by BS7671, and they are not submains either.

 

[JohnW2]

Are you not getting a bit confused here? ... Surely the CPC mentioned in that has to be the relevant CPC for the circuit in question. ...

Tha's what I wrote a couple of hours ago

However, I suspect that flameport's argument might be that whatever it is that receives the SWA (the 'CU' in your diagrams) is as much a part of the distribution circuit feeding it as it is of the 'local installation' - and that, as such, it is a 'point or accessory' of the distribution circuit as well as being connected to the local installation, and therefore that the regs can be interpreted as requiring the (appropriate, TN-C-S) earth to be 'run to' that place.

However, I'm far from convinced by that argument and, in any event, would be more comfortable not having (non-connected) TN-C-S and TT earths in the same enclosure - let's face it, under fairly exceptional circumstances, that would represent a hazard (in fact, the very same hazard as would exist if one didn't main bond an extraneous-c-p in a TN-C-S installation) even if all the power were switched off and isolated.

In fact, a (very risk-averse!) friend of mine deliberately terminated SWA in a JB on the outside wall of an outhouse because he didn't want any of the SWA armour, or anything connected to the armour, to enter the building.

Kind Regards, John

 

[JohnW2]

A submain is a separate circuit, and requires a CPC and testing just like any other.
It would be tested using X as the CPC and recorded on the certificate as one circuit.

I can understand that argument but, as I've just written, for a person working within SUNRAY's CU (or any other enclosure into which the SWA was terminated), it would represent exactly the same hazard (risk to life, in very rare circumstances) as would exist if one failed to bond an extraneous-c-p in a TN-C-S installation.

Kind Regards, John

 

[SUNRAY]

TT supplies on overhead poles are DNO items and not covered by BS7671, and they are not submains either.

When they span from building to building on a farm, fed by a DB after the meter and feeding another DB/CU?
When were overhead circuits removed from regs?

 

[SUNRAY]

A lively thread killed by a sensible question?

 

[JohnW2]

A lively thread killed by a sensible question?

... or even, if I dare to suggest, also a (in my opinion) fairly sensible comment (which immediately preceded the sensible question!) ...

... but, as I've just written, for a person working within SUNRAY's CU (or any other enclosure into which the SWA was terminated), it would represent exactly the same hazard (risk to life, in very rare circumstances) as would exist if one failed to bond an extraneous-c-p in a TN-C-S installation.

Kind Regards, John

 

[a546345]

OP back again. The new SWAs are laid to the far end, but there's been diggers working in the area so I want to test the cables. They are terminated into boxes but not connected to anything. I have a multimeter.

The r1+r2 testing seems aimed at rings where both ends of the ring terminate in the same place. This SWA is not a ring. I havent found a test procedure for a radial.

I was thinking of joining all cores of each cable together in my box at the supply end including the armour.

Then from the far end, test resistance of armour to each core, looking for the same low value, to prove continuity within each core.
Then from the supply end, test resistance between armour to house earth. (to test whether the outer plastic shield has been broken and the armour is therefore in contact with the ground.

I suspect this isn't quite right, and I'd rather do a recognised test - Anyone got a link to a test description please?