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Topic Title: Earthing Conductor connections to DNO lead sheath/swa cable
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Created On: 05 December 2012 08:39 PM
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 05 December 2012 08:39 PM
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Avatar for UKPN.
UKPN

Posts: 509
Joined: 17 January 2012

---I am writing this topic because there is confusion regarding
clipping to various types of DNO service cable in current use.

Micc services have a clamp over the pot similair to contracting
jobs which is screwed to a metalclad housing.

swa cable has a termination gland whereby the 951 clips onto
the gland not the cable.

swa also can be seen where the wires are plumbed solid so
the 951 fits securely without damaging the inner cores.

the lead type of cable was normally with a plumbed earth lead
but if a 951 was/is fitted it should be on a lead "built up" neck
of the cable just below the cut-out/neutral.

Regards.

consultants? one day they dont want you to bond a plastic origin copper main inside, next day they advise bonding pipes outside.
 05 December 2012 08:58 PM
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Avatar for OMS.
OMS

Posts: 19656
Joined: 23 March 2004

Originally posted by: UKPN

---I am writing this topic because there is confusion regarding

clipping to various types of DNO service cable in current use.

Micc services have a clamp over the pot similair to contracting

jobs which is screwed to a metalclad housing.

It will be a gland or a glandless earth tail pot then


swa cable has a termination gland whereby the 951 clips onto

the gland not the cable.

Or if done properly, it will make use of a banjo or a gland with a cable termination entry - you must know that putting a 951 on a SWA gland is as rough as a badgers - although probably good enough for a DNO I guess


swa also can be seen where the wires are plumbed solid so

the 951 fits securely without damaging the inner cores.

Nonsense - if done properly, the armouring will fit via two conical sections into a cast iron spreader enclosure


the lead type of cable was normally with a plumbed earth lead

but if a 951 was/is fitted it should be on a lead "built up" neck

of the cable just below the cut-out/neutral.

LoL - and when was the last time you wiped a tail onto a PILCSTA then ?

In most cases, there is no "built up" wipe - the BS951 is usually straight on the lead after the steel tape and before the flared wipe that closed the lead coating and expressed the paper winding of the conductors.

Shall I bring my tallow impregnated chamois along with a wide back boot knife and wooden core splitting wedges and show you how it's don - we could have a brew up on the gas ring inbetween boiling the moisture out of the paper tapes and preparted the solder pot and ladles

I may be consultant now, but rest assured I've stood in a few joint holes making good PILCSTA service connections - live. You learn quickly to keep your a**e off the trench wall and not to drop solder into the water - but you'll know all about that won't you ?



Regards.

consultants? one day they dont want you to bond a plastic origin copper main inside, next day they advise bonding pipes outside.

Go back and read it old son - where did I suggest bonding outside the zone of protection - my comments were limited to running in the bond, if and only if ,the gas service in the external cavity meter box was brought back into use by fitting a meter - the connection then being on the consumers side of said meter which, by definition is clearly inside the protected zone.

Do try and get it right, just once in a while -



Best Regards

OMS

-------------------------
Failure is always an option
 05 December 2012 10:13 PM
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johno12345

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 06 December 2012 10:04 AM
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Avatar for OMS.
OMS

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Joined: 23 March 2004

Originally posted by: johno12345

like this for example?

http://s764.photobucket.com/al...w¤t=DSC_0034.jpg


Exactly - if done "Old Skool", then the jointer would wipe a bulb of leaded solder over a stranded cable that was spilt into 3 and 3 strands with the 7th strand acting as a binder. The triplex strands would wrap the lead covering and the jointer would then solder the whole lot into place working the solder/lead up into a "bulb" that covered the joint completely. You had to control the temperature critically - too cold and you'd get a "dry" joint and you couldn't wipe it - too hot and the lot would end up on your boots - if you get it right, it's just like working with soft putty - easy peasy with plenty of practice

The modern equivalent is a constant pressure spring (Hepworth or similar)

A BS 951 clamp was never the best method - lead suffers from significant creep even at low temperatures - a little over tightning of the BS 951 puts a hell of a pressure on the lead and the underlying paper insulation - so either it goes bang, or loosens to the point of being totally ineffective in any fault condition - I've seen a few where the high(ish) resistance joint of a loose BS 951 has conspired to blow a bloody great hole through the lead when hit with a fairly close up earth fault.

I don't care what our resident DNO expert says - BS 951's on PILCSTA is bloody dog rough - and the primary candidates for doing it are the DNO's themselves - usually semi skilled guys or electricians who didn't have the skills to do the lead wiping.

If you come across it in your day jobs, then be wary of just giving the clamp a bit of a tighten - you may not be the first guy to have done that - and every time it's done the lead flows away getting thinner and thinner - don't be the guy who gives it the final tweak and it erupts in your face - there are usually big fuses backing up the service on the distributor main - very often, the system will have been designed to "burn back" into a fully developed SC rather than an earth fault - the energy let through will be huge - really fearsome

Regards

OMS

-------------------------
Failure is always an option

Edited: 06 December 2012 at 11:32 AM by OMS
 06 December 2012 11:25 AM
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johno12345

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the thing that puzzles me is that that installation was put in in 1958 and when i came along, it still had the original fusebox, cutout etc which makes me think that the BS951 clamp is also 1958, but i suppose there is nothing new about bodging!

that is the same clamp i mentioned in another thread where the DNO tightened it up when they changed the cutout - the original having a fused neutral
 06 December 2012 11:41 AM
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OMS

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That cut out is more recent than 1958 - Henly or Lucy units in grey grp would be late 70's I suggest

I would be suprised if a 1958 service had an original BS 951 clamp - if you could see under the terminal shiled you may find evidence of the "wipe" in there - or it's been removed when the cut out was swapped out - plenty of guys could strip back the lead and create a little "flare" and then terminate the cores - not quite so many could deal with the earth connection to the sheath by wiping - and of course it also means hot works inside the consumers premises

Regards

OMS

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Failure is always an option
 06 December 2012 12:05 PM
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johno12345

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sorry, i missed that vital part, i had it replaced a few years ago

it used to be this http://i764.photobucket.com/al...ohno12345/Kitchen6.jpg

when it was replaced, they trimmed the pitch to make it fit in the new cutout, but other than that, the cable wasnt altered
 06 December 2012 12:12 PM
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OMS

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OK - I'd still say that the BS 951 clamp is later than the original service cable - there was probably a bare stranded conductor originally and either the EB/DNO put the clamp on or more likley an electrician when the green and yellow was installed.

It may even have been an underground TT service originally - depending on how rural you are

Regards

OMS

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Failure is always an option
 06 December 2012 12:17 PM
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johno12345

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its not very rural, the transformer is across the road, on a concrete pad. there was no earth rod. when i moved in, there was no earth connected anywhere, not to the water or gas and that earth clamp was there but nothing connected to it. the fusebox was a 4 way wylex and it was done with 15a radials but of course had 30a fusewire in them so it definitely hadnt been rewired until i came along.

when i asked the dno, they said the supply was tn-s and the earth on that clamp tested out ok and thats the point at which all the new stuff was fitted. I cant work out when the clamp was fitted, but because of the way things were in the kitchen, i think its been there for at least 30-40 years
 06 December 2012 12:31 PM
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OMS

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OK - you have a better grip on the history of that service than I do - although I'd be pretty certain that the BS 951 clamp is later than the service itself.

Did you ever find a stranded uninsulated cable connection to a lead water main ?

Regards

OMS

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Failure is always an option
 06 December 2012 12:39 PM
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johno12345

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no, the water main is copper, i have stripped the house completely and found no uninsulated earth cables anywhere, did surprise me somewhat, no sign of clamps on the water main either. its all plastic now apart from a few inches under the floor.

gas was installed in the 70s which wasnt bonded either, but being newer than the electrics doesnt surprise me.

at one point i thought i had found an earth rod, but it was a piece of twine trapped under a paving stone!

I do agree that the clamp looks out of place, but i cant imagine when it might have been added, i dont think the previous owner will have done it, dont think he understood electics enough to do anything like that, some of the sockets he had added were done in 1mm 3 core t&e spurred off the original radials

interestingly, you could control all the lights in the house from a lightswitch in the hall, the bedrooms had pullcords but no lightswitches, apparently it was fashionable in the 50s to do that
 06 December 2012 10:52 PM
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alancapon

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Originally posted by: OMS
. . . BS 951's on PILCSTA is bloody dog rough - and the primary candidates for doing it are the DNO's themselves - usually semi skilled guys or electricians who didn't have the skills to do the lead wiping.

If you come across it in your day jobs, then be wary of just giving the clamp a bit of a tighten - you may not be the first guy to have done that - and every time it's done the lead flows away getting thinner and thinner - don't be the guy who gives it the final tweak and it erupts in your face - there are usually big fuses backing up the service on the distributor main - very often, the system will have been designed to "burn back" into a fully developed SC rather than an earth fault - the energy let through will be huge - really fearsome

I agree. One particular area here used BS951s on PILC cables. As we find them, we carry out an "earth upgrade" free of charge to the customer. This consists of removing the BS951 and joining the copper earth cable to the lead sheath using a proper "wipe" likel it should have been in the first place.

I have seen versions of these clips used on mains, and have actually managed to blow a hole in the lead with an arc through to the conductors while fault-finding. The resulting fireball was awesome (fortunately outside) and resulted in me sprinting to and tripping the HV/LV transformer at the local substation - I got there before any fuses cleared the fault.

Regards,

Alan.
 06 December 2012 10:58 PM
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peteTLM

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Originally posted by: alancapon

we carry out an "earth upgrade" free of charge to the customer.

Regards,


Alan.


Cough!! we should be so lucky here on the main land.
Over here we live in a PME obsessed, charge for maintaining their own equipment state.

-------------------------
----------------------------------------
Lack of planning on your part doesn't make it an emergency on mine....

Every man has to know his limitations- Dirty Harry
 06 December 2012 11:11 PM
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OMS

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For sure Alan - it takes some going to clear 630A+ plus distributor fuses in the fuse rack - tripping the TX manually is probably quicker - in either case, if you were the poor unfortunate who was standing at the service end it'll probably be too late and it's good night Vienna for your eyballs at least, if not the rest of your face.

Funny thing - it was gods representative of UKPN on earth who mocked me for suggesting looking away when withdrawing a service fuse - I'll accept none of use should be doing it without at least a face mask and gloves - but back in the day, it wasn't a bad shout if things did get a bit iffy - I'd rather be looking away from a arc blast to the lead than straight into it for sure.

I guess you guys out there are still giving proper training to apprentice fitter jointers and the like in the art of paper lead then ?

Regards

OMS

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Failure is always an option
 06 December 2012 11:23 PM
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alancapon

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Yes. I think we are the last in the British Isles to still cover hot lead work. We no longer use hot lead work for the conductors - shear bolted connectors is the order of the day, but the earth is still "plumbed" where it is a PILC cable. We still installed lead for mains until recently - we were stopped by not being able to by the cable, rather than any other reason. We have been using XLPE concentric and split-concentric service cables for a while now. Where a customer has a PILC service though, we would still rather plumb the lead, rather than using a clip.

Regards,

Alan.
 06 December 2012 11:53 PM
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OMS

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I'll know where to come if I need a gang of jointers for some existing PILC/SWA modifications to a big client site then Alan -

Have you seen UKPN's new avatar - fantastisch -

Regards

OMS

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Failure is always an option
 07 December 2012 12:27 AM
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johno12345

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i cant work out what cable its been put on, is it pilc?

One thing I have learnt over the years is that every type of cable has a correct method of terminating it, but there is always a way to do it wrong and bodge it. I remember when we started using SY flex and some of the terminations were a right bodge, ask the supplier, and low and behold, a proper gland for it.

oddly enough, none of the termination methods we use involve a BS951 clamp

if an electrician did work for me that involved putting one on a SWA, gland or otherwise, I wouldn't be best pleased
 07 December 2012 01:03 AM
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OMS

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I suspect it is yes - there's a vague outline of steel tape below the clamp - but difficult to say from a photo that size

OMS

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Failure is always an option
 07 December 2012 07:44 PM
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UKPN

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---its PILCSWA, 100amp. house built in 1975 the owner tells
us, so our favourite forum consultant will tell us the "imperial"
size. the tape is covering the strands low level, and a rubber shroud is
placed on the two cores above, below the separate cut-out and neutral block.
the owner tells us the earth clamp was there from new, put on by the
old eastern electricity board.
earth size is 6sqmm (equiv)

why were we there? to check the earth loop, which was good. 0.5
point is this type of clip correctly installed gives good service almost 40 years in this case, surprising.

Regards.

Crack on???
 07 December 2012 07:49 PM
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UKPN

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---and another thing, note the small round disk (blue phase)
attached to the rubber shroud, handy if identifying a lost phase.

Regards.
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