Catenary wire

[the pict]

Any one heard of earthing cat wire,
Pict

 

[44ALLAN]

Any one heard of earthing cat wire,
Pict

Only if it's on tray plate

 

[the pict]

I,v heard of earthing the tray(s) but cat wire over head for 25mm armour never, but a guy reckons it,s a must but no metion in the book only a referance to table 42a item 35
P

 

[Geordie Spark]

I,v heard of earthing the tray(s) but cat wire over head for 25mm armour never, but a guy reckons it,s a must but no metion in the book only a referance to table 42a item 35
P

Ask him for the reg. number?

 

[Adam W]

Any one heard of earthing cat wire,
Pict

Nope, that's a new one on me.

 

[the pict]

He is a very clever chap I think I will try to find out his thinking on this, he is ex power station type so could be somthing unique to that
Pict

 

[Geordie Spark]

He is a very clever chap I think I will try to find out his thinking on this, he is ex power station type so could be somthing unique to that
Pict

Yes, I think I would tread a bit carefully here too. Blokes like this could teach you a lot - a bit like our own Engineer54, Tony & Blindnetpaul.

 

[chrish_1977]

Just politely ask him why, then he should tell you his reasons why, can't be fairer than that

 

[44ALLAN]

I,v heard of earthing the tray(s) but cat wire over head for 25mm armour never, but a guy reckons it,s a must but no metion in the book only a referance to table 42a item 35
P

Soz mate I was joking

 

[Engineer54]

I don't think there is any regulatory requirement for earthing catenary wires, but i know it was done for the few we had at the factories i served my time at!!
Again these were metal poles not wood poles. Don't think i've ever had the occasion to run a catenary supported overhead cable, since either!! lol!!

 

[Deleted member 9648]

Years ago I used to earth them for short overheads to garages etc....but in those days it was common practice to strap a bare T/E to the cat. These days it would always be SWA or plastic conduit so there would be no point in earthing the cat wire.

 

[driverman]

At the Electric Boards years ago, we always earthed bare catenary wires. Later though started to use insulated catenary wires.

 

[Engineer54]

I remember one of the medium sized warehouses lighting, being completely wired in a made for purpose high tensile steel wire catenary system, with proper system take-off boxes, the whole nine yards so-to-speak. No idea if such systems are still available or still used. Can't remember ever having any problems with the system during the time i was there!!

Pretty sure that the catenery system was fully earthed too.

 

[cobrauk]

If it can become live because of what you are installing on it, then the answer would have to be yes it needs earthing

 

[somersetsparks]

We always used to earth the catenary with 4mm when it was attached to metal poles, You won't find a specific requirement to do it though.

 

[Knobhead]

I remember one of the medium sized warehouses lighting, being completely wired in a made for purpose high tensile steel wire catenary system, with proper system take-off boxes, the whole nine yards so-to-speak. No idea if such systems are still available or still used. Can't remember ever having any problems with the system during the time i was there!!

Pretty sure that the catenery system was fully earthed too.

Not seen them for years, we had a few set ups like you mention. they were all removed after the catenary broke at another works. They were on steel hangers in steel framed buildings so be default they were earthed.

 

[Outspoken]

Whilst there is an argument that a cat wire need not be bonded to earth, I think that within the Regs there are also arguments that it should be because it is an extraneous conductive part of the wiring systems, no different in essence to trunking, ladder rack, basket or conduit, and unless they were made from non-conductive materials we never balk at bonding these, so within s411 (If memory serves) it should be bonded and as part of s522 concerning the Selection and Erection of Wiring Systems (again if I have remembered the section correctly)

I would also proffer the argument that if this is between buildings and could be subject to the effects lightning (Directly or indirect by induction) then is should be bonded to earth as per BS EN 62305..

 

[somersetsparks]

Whilst there is an argument that a cat wire need not be bonded to earth, I think that within the Regs there are also arguments that it should be because it is an extraneous conductive part of the wiring systems, no different in essence to trunking, ladder rack, basket or conduit, and unless they were made from non-conductive materials we never balk at bonding these, so within s411 (If memory serves) it should be bonded and as part of s522 concerning the Selection and Erection of Wiring Systems (again if I have remembered the section correctly)

I would also proffer the argument that if this is between buildings and could be subject to the effects lightning (Directly or indirect by induction) then is should be bonded to earth as per BS EN 62305..

I don't think there is a requirement to bond it, same as a piece of steel conduit used to carry t+e,
however I would probably and usually bond it.

 

[Engineer54]

Whilst there is an argument that a cat wire need not be bonded to earth, I think that within the Regs there are also arguments that it should be because it is an extraneous conductive part of the wiring systems, no different in essence to trunking, ladder rack, basket or conduit, and unless they were made from non-conductive materials we never balk at bonding these, so within s411 (If memory serves) it should be bonded and as part of s522 concerning the Selection and Erection of Wiring Systems (again if I have remembered the section correctly)

I would also proffer the argument that if this is between buildings and could be subject to the effects lightning (Directly or indirect by induction) then is should be bonded to earth as per BS EN 62305..

The systems you are describing are ''Exposed'' Conductive Parts not Extraneous. Like wise you would ''Earth a catenary wire, not bond it, as they too, would be unlikely to bring an extraneous earth potential into a building. The catenary wire would be a wholly external installation fixed to outside structures, or wholly internal installation...

 

[Deleted member 9648]

Whilst there is an argument that a cat wire need not be bonded to earth, I think that within the Regs there are also arguments that it should be because it is an extraneous conductive part of the wiring systems, no different in essence to trunking, ladder rack, basket or conduit, and unless they were made from non-conductive materials we never balk at bonding these, so within s411 (If memory serves) it should be bonded and as part of s522 concerning the Selection and Erection of Wiring Systems (again if I have remembered the section correctly)

I would also proffer the argument that if this is between buildings and could be subject to the effects lightning (Directly or indirect by induction) then is should be bonded to earth as per BS EN 62305..

I'd stongly suggest a read of part2 (definitions) of 7671. Extraneous conductive parts and conductive parts.

 

[Outspoken]

The systems you are describing are ''Exposed'' Conductive Parts not Extraneous. Like wise you would ''Earth a catenary wire, not bond it, as they too, would be unlikely to bring an extraneous earth potential into a building. The catenary wire would be a wholly external installation fixed to outside structures, or wholly internal installation...

I would suggest you use the Index of 7671 and look under Extraneous Conductive Parts > Bonding and that is the section it points you too, just double checked in case my memory was off..as I admitted it could be in my post.

I'd stongly suggest a read of part2 (definitions) of 7671. Extraneous conductive parts and conductive parts.

I strongly suggest that i do know the difference, and if you check my posts I did not state whether the cat wire should or should not be bonded because I do not have an opinion on the matter, I have only offered up a couple of points in the regs that could be used to justify a demand for bonding.

 

[somersetsparks]

if it were extraneous it would require main bonding of the appropriate size. I could see this being the case if it was attached to a metal pole in the ground. however the wire itself and any brackets wouldn't meet the definition of an extraneous conductive part or an exposed conductive part, even if used to carry t+e and just attached to masonary etc. between two buildings.

 

[Engineer54]

If someone can please explain to me how a catenary wire is ever going to bring an extraneous earth into a building?? Or come to that, why you would ''bond'' rather than earth, a catenary wire??

 

[Engineer54]

I would suggest you use the Index of 7671 and look under Extraneous Conductive Parts > Bonding and that is the section it points you too, just double checked in case my memory was off..as I admitted it could be in my post.



I strongly suggest that i do know the difference, and if you check my posts I did not state whether the cat wire should or should not be bonded because I do not have an opinion on the matter, I have only offered up a couple of points in the regs that could be used to justify a demand for bonding.

I don't need to check, i know full well, that the items you suggest are ''Extraneous Conductive Parts'' are NOT!! They are part of an electrical installation that need to be ''Earthed'' not main ''Bonded''!!


Likewise Wirepuller didn't say anything about cat wires, he just rightly pointed you to the definitions of extraneous conductive parts and conductive parts in BS7671.

 

[Deleted member 9648]

I strongly suggest that i do know the difference, and if you check my posts I did not state whether the cat wire should or should not be bonded because I do not have an opinion on the matter, I have only offered up a couple of points in the regs that could be used to justify a demand for bonding.

You clearly dont.
That is evident from your posts.
Sorry to be persistant on this but one of the constant frustrations of this forum for me is the number of electricians who lack basic understanding of the difference between earthing and bonding,when both are appropriate or not,and the use of incorrect terminolgy which only serves to feed the confusion.
You cant have 'An extraneous conductive part of the wiring systems' ,it's not possible.

 

[garyson02]

Any one heard of earthing cat wire,
Pict

Nope, that's a new one for me.

 

[D Skelton]

I don't need to check, i know full well, that the items you suggest are ''Extraneous Conductive Parts'' are NOT!! They are part of an electrical installation that need to be ''Earthed'' not main ''Bonded''!!

You clearly dont.
That is evident from your posts.
Sorry to be persistant on this but one of the constant frustrations of this forum for me is the number of electricians who lack basic understanding of the difference between earthing and bonding,when both are appropriate or not,and the use of incorrect terminolgy which only serves to feed the confusion.
You cant have 'An extraneous conductive part of the wiring systems' ,it's not possible.

Sorry bud, but these two have pretty much nailed it on the head.

 

[telectrix]

Sorry bud, but these two have pretty much nailed it on the head.

but should the nail be earthed or bonded?

 

[D Skelton]

Ah, good question! I think as this particular nail is reinforced plastic, then neither! Now stop advocating the earthing/bonding of plastic Tel! You'll confuse the 5WWs

 

[Outspoken]

Sorry bud, but these two have pretty much nailed it on the head.

I have to disagree, but as I only stated that there is an argument for both sides of the coin, and really don't care either way as I have never and never would earth centenary wire unless there was an exceptional reason to, for me it is a moot point and I refer the previous two back to the definitions in the regs because they classify centenary as an EXTRANEOUS and not an EXPOSED conductive part...but hey ho.

 

[D Skelton]

Where? If the regs classify catenery wire as extraneous then they're wrong! You're right in the catenery wire is neither exposed or extraneous in 99% of circumstances however if there is a risk that it could become live due to a faliure in basic insulation then it would be an exposed, not an extraneous conductive part, therefore it would require earthing, not bonding.

 

[Silly Sausage]

I'd take what OS says sometimes, with a pinch of salt.
I vaguely remember, from his introductory speech, he likes to be 'controversial', hence his name (his words)!!!!


Or he's making some really basic mistakes!?!?!

 

[D Skelton]

I don't mind controversy at all, if anything I relish it! But it has to be reasoned!

 

[Outspoken]

I'd take what OS says sometimes, with a pinch of salt.
I vaguely remember, from his introductory speech, he likes to be 'controversial', hence his name (his words)!!!!


Or he's making some really basic mistakes!?!?!

Actually I know the definitions..

Let me quote if I may, and you can take with a pinch, shovel or bucket of salt all you like.

Exposed-Conductive-Part. Conductive part of equipment which can be touched and which is not normally live, but which may become live under fault conditions.

Extraneous-Conductive-Part. A conductive part liable to introduce a potential, generally Earth potential, and not forming part of the Electrical Installation

You will find the above on page 27 and page 28 respectively.

Now catenary wire is not part of the equipment, it is a conductive part that is likely to introduce a potential, namely an Earth potential, but which, under fault conditions may be at a different potential to the general mass of Earth, thus introducing a potential shock hazard.

Now I would wholly agree that neither definition is exact in covering catenary wire, but then we have to fall back on good understanding and experience, the catenary wire is never an exposed conductive part as it is not part of the electrical installation, no more so than the the steel sections of a dry lined wall are or the radiators in a wet central heating system, and as such the definition of Extraneous Conductive Part is correct.

Now perhaps you wish to write a more accurate definition, be my guest, it is needed to be honest, but I really can't see the IET and the BSI rewriting anything for the 1/1 billion chance that the catenary will become live in the literal sense.