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Cable jointing (UK) #125079 02/25/07 07:47 AM
Joined: Aug 2001
Posts: 7,520
pauluk Offline OP
Two old cable joints, from TrimixLeccy:

[Linked Image]

[Linked Image]

[Linked Image]

[Linked Image]

[Linked Image]

[This message has been edited by pauluk (edited 02-25-2007).]

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Re: Cable jointing (UK) #125080 02/25/07 02:58 PM
Joined: Jan 2007
Posts: 38
TrimixLeccy Offline
The first 3 pics are of a cable 'joint' we had to cut out live from an old factory. The smaller wire on the left [pvc or asathene] fed the complete joint; a slight anomally in sizes I think you will agree. I have no idea why it was like this, especially as some of the cables are black and some are red. There is also more lead in the left cable lug than there is cable. This cable is V.I.R. which is Vulcanised insulated rubber coated in a cotton braid. The rubber deteriorates and cracks, then the damp causes the cotton covering to become live!!! This type of cable was usually installed within metal conduit [this was in a wooden box]. It was also used as Main outgoing meter cables [tails]...horrible stuff. The blue paper at the top is the size of a credit card to give you an idea of scale. Eventually, you will be pleased to know, it was all ripped out and replaced with pvc... [Linked Image]

The lower 2 pics are of an old Joint box made of 'white cast metal' body and a tinned brass lid. The cables are all lead covered with twin rubber covered cores inside. The earth is derived from the lead sheath and continuity is accomplished by the screw being forced into the lead sheath. The connectors inside [wire-nuts? see,I am learning the US terms!] are made of porcelain. These were made by the British Screwit company and came in 2 sizes. The ones shown were called 'normals' whilst the smaller ones were called 'midgets'. The joint was as good as the day it was installed and STILL passed a 1000v Insulation test and Earth continuity test when it was removed. The connectors are wrapped in 'Blakely tape', a cotton covered rubberised type of tape.

Re: Cable jointing (UK) #125081 02/25/07 05:15 PM
Joined: Dec 2005
Posts: 860
The cables from the old factory are also still in good nick, bolted with a good quality brass bolt.
Because of the other colours, blueish and red jointed together it may have been done to run a feed which used to be 3 phase and made off as a single phase feed to a distribution board.
It is also possible that it was a CT metered supply in the past, which was downgraded to a 63 Amps supply hence the relatively thin 16 mm² feed, feeding the bigger cables.

The photo's from the joint box shows the immaculate condition of those old rubber insulated wires.
It is great to see that it passed the 1 kV insulation test so well.
Those cables tend to become brittle behind light switches where perhaps a continuous flow of draught air dries up the rubber insulation.
We still have quite a few of those around in the older houses in New Zealand.

The product of rotation, excitation and flux produces electricty.
Re: Cable jointing (UK) #125082 02/25/07 08:46 PM
Joined: Aug 2001
Posts: 7,520
pauluk Offline OP
Because of the other colours, blueish and red jointed together it may have been done to run a feed which used to be 3 phase and made off as a single phase feed to a distribution board.

Sure looks like red, white, and blue on the bundle of three at the top (white being our B-phase color before it was changed to yellow in the mid 1960s).

Re: Cable jointing (UK) #125083 02/26/07 09:45 AM
Joined: Jan 2007
Posts: 1
SPARKYPRO_1911 Offline
Junior Member

Re: Cable jointing (UK) #125084 02/26/07 01:20 PM
Joined: Jan 2007
Posts: 38
TrimixLeccy Offline
Yep, still in use until the second I cut through it [and after!] I cannot remeber where it came from though. You would think I would remember something like that, but I come across so many jobs done by 'Factory Maintenance Engineers' motto...."if it is not broken then keep repairing it until it is". Double nutted though , so at least they tried.
Just checked the colours again....they are ALL either red or black. The reds are cotton covered rubber VIR. and the blacks are double covered rubber, probably what we used to call TRS [Tough rubber sheathed] The small cable on the left is PVC or Asathene approx 7/.064 which is about 6mm^2 ish. The others are about 16mm^2 or 25mm^2 equiv. could even be 35mm^2!!

More interesting pics to follow when I get time.

Re: Cable jointing (UK) #125085 03/01/07 01:47 PM
Joined: Mar 2002
Posts: 360
Trainwire Offline
I run into similar joints when I am working on old railroad cars.

The heavy old wire was originally for a 32 volt dc system, low voltage, high current, big wire.

At some point along the line, somebody converted the whole shebang to 110, or 240 volt ac. Higher voltage, lower current, don't need such big wires. Big wires can carry low current, they just don't get as hot the rubber insulation lasts longer. [Linked Image]

I'd bet a fried chicken tv dinner that's what happened here.


Re: Cable jointing (UK) #125086 03/02/07 07:23 AM
Joined: Dec 2001
Posts: 2,492
Texas_Ranger Offline
I've seen such screw and nut connections on 1mm2 copper wire, cloth covered, in residential wiring! Prior to the invention of "choc blocks" that's how wires were spliced in Austria! Even in a 1965 house (admittedly very conservative construction) all original splices are like that. To be honest where I didn't have to touch them I just retightened the screws and wrapped it with new cloth tape.


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