People's opinion....

M

Mr s

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Afternoon to all.....


i have a question to ask all of you and wondered if any of you could help..

I was carrying out some work on one of the other sparks jobs today and questioned why he had three earths at a socket. It is a ring main. Now before you say it it is not a fly lead as it's in plastic dado trunking. Now his reply was that we have been told from now on when using swa to dado trunking to take a tembi clip from the wire sheaf to the socket outlet. I have never heard of this before but I am curious as to what you think. My thoughts where that the sheaf will be earthed via the trunking at the board end with a bolted down banjo and we are using three core so has a core for its cpc.

any feed back would be appreciated..........
 
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It may be if the sockets are for computers and they want to increase the CSA of the earthing put if its only to one socket then I can't see any reason for it, as you have said the swa is terminated at the board end so no reason to do it, By the way whats a Tembi clip,
 
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Mr s said:
Afternoon to all.....


i have a question to ask all of you and wondered if any of you could help..

I was carrying out some work on one of the other sparks jobs today and questioned why he had three earths at a socket. It is a ring main. Now before you say it it is not a fly lead as it's in plastic dado trunking. Now his reply was that we have been told from now on when using swa to dado trunking to take a tembi clip from the wire sheaf to the socket outlet. I have never heard of this before but I am curious as to what you think. My thoughts where that the sheaf will be earthed via the trunking at the board end with a bolted down banjo and we are using three core so has a core for its cpc.

any feed back would be appreciated..........
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What size is the SWA? how long is the run? people opinions differ on this subject but IMO it's not ideal to run one cable to feed a Ring FC assuming that's what he has done, as I said that's my opinion
 
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It's about ten meters from the board. Tenby clamps perhaps I should say, what you use to earth copper pipe work etc.... He has run two cables fro the ring main, as I said a three core so be a bit difficult to complete a ring. It's a print copy area so will have printers etc etc. zs readings where 0.11 so not a high zs. And yeah he has said on every job. This guy thinks he is the nuts, he is the firms nic man so what ever he said's the director wants but when I see this I could not see any point to it and would rather not squeeze three earths in one terminal if there is no reason to do so.... It's commercial in London and we use swa in most power situations now days....... It's on an rcbo so so just can't see a reason for this....
 
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Not a good idea to clamp earth straps to swa sheaths

if its suitiably earthed the other end its not really required, however.......

still a bit of a rough way to do things, why not terminate the swa into a suitiable box then feed the dado from there


im sure if his nic area engineer saw his install methods he would put him straight
 
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You should not use one of these clips as it can damage the inner cores of the cable by putting to much pressure on them if your going to terminate the swa it needs to be done with the correct gland
 
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As above whatever the reason about the earthing link its clear that the use of a tenby clip is poor workmanship and I would challenge the competence of anyone seen doing this, why hasn't a correct gland and banjo earth ring been used or other recognised earth method?
 
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Thank you very much for your feed back and from what you have said it is as daft as I thought. Thing is I didn't want to challenge him because he is the man who knows it all APPARANTLY.

thanks again people
 
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If it a PVC SWA to BS5467 and you are use one of the core/conductor as a circuit protective conductor then armouring must only be terminated at the supply, (to provide protection against mechanical damage or piercing of the amoured) at the load end it must be terminated into a not conductive box or trunking. This is a requirement of BS 5467 and not the regulation. As it be described, under fault condition most the the fault current will flow through the cable and only a fraction through the armouring, this will produce circulating current, that may cause damage to cable. Read Paul cook commentary on IET regulations.
 
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Further section 5 or BS5467 requires that all armoured are terminated by manufacturer glands and if armoured is required to carry large fault current then a flying lead must be terminated from MET to the armoured gland via earth cable and earthing ring (commonly refereed to as Bango) at the supply end and same arrangement at the load end, no reference is made in the document of using a BS951 earthing clamp as previously described. last final point the earth ring can be placed inside and there is no need to drill and bolt it to the metal casing of the steel trunking, box, distribution board, all you need to do is nut and blot the fly lead to the earthing ring, (I would advice minimum of 10 mm CSA for fly lead)
 
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Cyril Molony said:
If it a PVC SWA to BS5467 and you are use one of the core/conductor as a circuit protective conductor then armouring must only be terminated at the supply, (to provide protection against mechanical damage or piercing of the amoured) at the load end it must be terminated into a not conductive box or trunking. This is a requirement of BS 5467 and not the regulation. As it be described, under fault condition most the the fault current will flow through the cable and only a fraction through the armouring, this will produce circulating current, that may cause damage to cable. Read Paul cook commentary on IET regulations.
Click to expand...


Really! Never heard that one before, millions of non-compliant swa runs out there then

is that why most wholesalers stock xple?
 
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Mr s said:
It's about ten meters from the board. Tenby clamps perhaps I should say, what you use to earth copper pipe work etc.... He has run two cables fro the ring main, as I said a three core so be a bit difficult to complete a ring. It's a print copy area so will have printers etc etc. zs readings where 0.11 so not a high zs. And yeah he has said on every job. This guy thinks he is the nuts, he is the firms nic man so what ever he said's the director wants but when I see this I could not see any point to it and would rather not squeeze three earths in one terminal if there is no reason to do so.... It's commercial in London and we use swa in most power situations now days....... It's on an rcbo so so just can't see a reason for this....
Click to expand...

Any and all SWA terminations should always be via a correctly sized SWA gland (or a made for purpose SWA clamp that you often find in street lighting columns). Anything else does not comply with manufacturer's instructions, or anything else come to that. The Tenby clamp method is just about the worst thing you can do to a SWA, it will crush and over time damage the insulation of the cores!!

Connecting 3 X 1.5/2.5mm CPC's into an earth terminal is the least of your worries, (they won't be exactly ''squeezed in'' either) besides most socket outlets have 2 CPC connection points, only cheap and nasty examples provide only one CPC point these days...

Personally i always earth both ends of SWA cable whether you need to or not , can't really see a reason not too, unless your intention is to isolate the the supply earthing system for one reason or another....
 
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quote_icon.png
Originally Posted by Cyril Molony
If it a PVC SWA to BS5467 and you are use one of the core/conductor as a circuit protective conductor then armouring must only be terminated at the supply, (to provide protection against mechanical damage or piercing of the amoured) at the load end it must be terminated into a not conductive box or trunking. This is a requirement of BS 5467 and not the regulation. As it be described, under fault condition most the the fault current will flow through the cable and only a fraction through the armouring, this will produce circulating current, that may cause damage to cable. Read Paul cook commentary on IET regulations.
Click to expand...

What a load of old hogwash!! So what happened in years gone by when there wasn't any banjo type earth connections and the metal glands were connected directly to metal switch boards, DB's back boxes and just about everything else that was metal?? Even today, most SWA cables are being connected between metal enclosure, be they 3 core, 5 core or whatever (using 1 core as the CPC), how are you going to isolate the load end of that SWA from the metal enclosure??


Circulating currents, ...my arse!! Show us this requirement in BS5467, because i'm pretty sure it would have been included if not in BS7671 itself, but certainly in it's OSG or other G' Notes!!! Not in some obscure commentary on the IET Regulations that few would actually own....
 
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Welchyboy1 said:
Really! Never heard that one before, millions of non-compliant swa runs out there then

is that why most wholesalers stock xple?
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The IET hold licienced copies of most british standards relevant to the regs, if you get the chance visit and look for section/part 5 of Bs 5467.
 
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it most case the earth bar is the met, especially for domestic installations, I agree in commercial/industrial you may have and external MET, but it may also be incorparated into the consumer unit/distribution board.
 
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Geordie Spark said:
As a Time Served Precision Engineer I have to say that thing is total cack!!!
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I have used them quite a few times and i thought they were decent? They have small serated teeth on the bottom to dig into any metal work they are tightened down on to, they have one grub screw for tightening a crimp into and also an allen grub screw so they don't come loose over time! I much prefer them to drilling out banjo holes!

Wiska also do some earthing connections like these.. although i didn't like the look of them too much!
 
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Cyril Molony said:
If it a PVC SWA to BS5467 and you are use one of the core/conductor as a circuit protective conductor then armouring must only be terminated at the supply, (to provide protection against mechanical damage or piercing of the amoured) at the load end it must be terminated into a not conductive box or trunking. This is a requirement of BS 5467 and not the regulation. As it be described, under fault condition most the the fault current will flow through the cable and only a fraction through the armouring, this will produce circulating current, that may cause damage to cable. Read Paul cook commentary on IET regulations.
Click to expand...

Why would a BS covering the construction of a particular cable dictate the method of it's installation ? And why would BS7671 which dictates the requirements for cable installation not mention this ?
 
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Tidy Max said:
I have used them quite a few times and i thought they were decent? They have small serated teeth on the bottom to dig into any metal work they are tightened down on to, they have one grub screw for tightening a crimp into and also an allen grub screw so they don't come loose over time! I much prefer them to drilling out banjo holes!

Wiska also do some earthing connections like these.. although i didn't like the look of them too much!
Click to expand...

I'm confused. Are we now saying that piranha nuts are rubbish? I thought the general consensus was that they were the way forward, especially when glanding off into powder coated metal enclosures, as far too few sparks realise that the powder coating is non-conductive and therefore the paint underneath the banjo should be scraped off. The piranha nut does this for you when tightening down onto the enclosure.
 
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southsea1201 said:
Pirahna nuts are great. I've used them many times and those metal teeth really grind in. If you have loads of joints on a job they are deffo worth buying as they represent a real time saver.
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I've used a shed load of them on a recent job, glanding off into plastic adaptable boxes for continuity of the SWA. Neat job and a lot less fiddly than bolting cables onto banjos.

Good price if you buy the SWA (brand) packs that include the gland, nut, and variety of sized lugs.
 
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Mr s

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