People's opinion....

[Mr s]

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..........

 

[Pete999]

Yes see pictures on link to see how its done

What link

 

[Mr s]

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

 

[Geordie Spark]

Yes see pictures on link to see how its done

As a Time Served Precision Engineer I have to say that thing is total cack!!!

 

[Pete999]

As a Time Served Precision Engineer I have to say that thing is total cack!!!

Same as him

 

[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.

 

[stevethesparks]

As a Time Served Precision Engineer I have to say that thing is total cack!!!

Not used them myself but so-far have only seen good reviews about them. So what's wrong with them?

 

[Cyril Molony]

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)

 

[Welchyboy1]

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.

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

is that why most wholesalers stock xple?

 

[Engineer54]

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....

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....

 

[Engineer54]

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.

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....

 

[LeeH]

a flying lead must be terminated from MET to the armoured gland via earth cable

That's bollox. Just think about the practicability of doing that to every SWA in a installation bigger than a house.

 

[stevethesparks]

Nice one Cyril

 

[Cyril Molony]

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

is that why most wholesalers stock xple?

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.

 

[Pete999]

That's bollox. Just think about the practicability of doing that to every SWA in a installation bigger than a house.

Got a feeling Cyril is confusing the MET with the earth bar in the DB, on the other hand???????

 

[Cyril Molony]

That's bollox. Just think about the practicability of doing that to every SWA in a installation bigger than a house.

LeeH really read section 5 of BS5467