How to, Underground cable joint

Haven't done one of these for a while so i thought i would take a few piccies for you all. I cant believe how small they make the torpedoes nowadays. I would use the next size up in future. Note how i did not bother to mark the cables, one being R, Y, B, BK & the other B,BK, G & BL. Since its all embedded in resin now it will never be seen again

Here's the kit


Here's the instructions


Here's the cables to be jointed. This is feeding a shed, yes its a 16mm 4 core running 3 phase. Builder cut it when the swimming pool was removed. The sheds another story. Note this years fashion in boots


The cables cut back to size


The cable couplers. Supplied with the Alan key, no torque settings but head shears when tight


The spacer thats meant to go between the cores, i did manage to get it almost in-place


The finished connections


This is the earth connector kit known as a constant pressure spring


Couple of close ups of the earth connection. Instructions say to double back under spring after 1 complete loop



Casing put on and ends taped to hold back any seepage


The two part resin, you pull a separator apart on the foil packet and need the goo together for two minutes


The finished job. You wear the supplied gloves whilst handling the resin

Why are they never 'big enough'??? I have done thousands of them over the years and always went up to at least the next size of shell. Try doing a 'breach' on a 50mm 4 core,.........you need to be an enthusistic amateur Gynaecologist to be in with even half a chance! I used to struggle with the joints 'in fresh air'...much easier in the ground so they were supported. So, brainwave time. After seeing a Plumber do a straight lead joint using a bar clamp, I got one. Prob not even made now. It is like a metal bar with 2 sort of 'school chemi lab retort clamp affairs at each end'...it is the "dog's back wheels" should you ever need one.....................I'd post a pic if I could find it!........ :coat

Thanks for that Slips

...

That looks good. I would have thought you could improvise 'Kerching's' idea using a wooden baton and a couple of spring clamps.

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I think resin joints are liker buses you may do one then not one for ages then probably do a few together. This brass doesn't seem to be like it used to. Had some brassie looking earth clamps for earth rods a few weeks back they would split as soon as you put any pressure on them couldn't get cable tight at all. The copper looking ones are certainly a lot stronger.

Pratley 2 Way SWA Thru Box - Under Ground IP68 C/w Glands & Shrouds - BOX SIZE 0 - QVS Electrical Supplies | Electrical Wholesaler

so much quicker....

matt,

Have seen these, but I do admit I have never used them, just not sure, have always used resin poured joints as once encapsulated, IF made correctly they are extremely reliable, and I mean decades.

Not knocking your suggestions, just saying, no experience of this new fangled stuff!!!

There are others too, I think Canoey used Raychem ones?

Looked up this thread for something else, 15 months on the sheds finished so i will upload some pics.

You didnt insulate the brass connectors with PVC tape or the spring clips on the SWA, and did you abraid the outer PVC sheathing of the cable just as it enters the joint shell so the resin will adhere to it.

streetlighter said:

You didnt insulate the brass connectors with PVC tape or the spring clips on the SWA, and did you abraid the outer PVC sheathing of the cable just as it enters the joint shell so the resin will adhere to it.

Click to expand...

Ah....the voice of experience!.....how many times have you stood there and watched the resin gently dribble out of the plastic shell ( obviously never packing the leaking ends with mud, clay, tea towels, wooly hat, gloves, gaffer tape etc)?

We always used to insulate the connectors with 'patch'....probably not even made any more. It was a sort of self amalgamating tape but in a roll the size of flashband. Might have been handy if you ever had to insulate a tool or similar in an emergency, not that I ever felt the need....obviously!

I did prime and tape up the ends before fitting the cover . I also scored the pvc as can be seen in the pics. I have never wrapped the connectors and it did not say to do so in the instructions. The plastic seperators hold the cores apart. Why do you think tape should also be used ?

Canoeboy said:

http://www.jointingtech.co.uk/category.asp?categoryID=49

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That's the stuff!

Didn't think they still made it to be honest

Why oh why doesn't somebody invent some form of program that you can use on the tinterwebnet to search for things?...... Some sort of machine, an engine maybe?.....I'll Goog..................oh hang on

Just saying

Its good practise to insulate the brass connectors and its how i was taught to do it plus it was a requirement for one of our clients. Ive done loads of resin filled joints over ten years on highway lighting

Hi there and thanks for an informative thread !!

I too have had the misfortune to have to carry out a number of underground cable joints and yes why on earth are the cases so b****y small !!!

One thing I don't like about the kits you are using in the photos is that the constant pressure spring is being applied directly to the cable armour, which is in turn pressing straight onto the soft PVC bedding underneath. To be frank this is not a good practice as there should be a metal ferrule underneath the armour to provide support and mechanical compression strength for the earth connection. I suppose its OK if the cable is RCD protected and there is only ever likely to be a few milliamps flowing through the earth/CPC/armour in the event of a fault, but for a non-RCD protected cable where the full fault level will be passed through the joint it's integrity could easily be in question. The connection as shown would only have a fraction of the fault carrying capacity of the same joint using ferrules under the cable armour.

I'm surprised that CTL Clearcast (a big player in this sphere for a number of years) have omitted this.

Steve C.

All the ones I have fitted do have a ring that goes under the SWA.

Thanks 2 Steves. I have only done one more torpedo joint since this & that did not have or mention a 'collar' as you suggest, I see where your coming from. Hopefully they have done tests on this kit, it amazes me the current that Wago connectors can carry when you can easily twist the cable around and there must be only a very small connection point between the spring and the cable.

PS, the job pictured did have an additional Cpc run along side the SWA .

Just thinking.......   I was never taught nor does the instructions tell you to wrap & insulate  the connections  or earth as a few people have suggested. If you were to then you have not followed the manufacturers guide and so have broken BS7671 ?    ;

taping the brass connectors is a bit pointless when you can get over 2 MegOhm IR is less than 10 mins, ie still wet!. Tape has no insulation value (it obviously works a bit). Spacer is there to keep joins apart sufficiently to allow resin to insulate between connections.

collars - that spring doesn't exactly crush armour into inner PVC. The way it works spreads load in a very even way without exerting huge forces inwards.

Taping or patch is useful if you have to do one live! Also don't need a collar as the resin will go hard and prevent the armours from digging in

This thread keeps getting dug up ( not like that joint which is still holding strong) Anyhow thats a good point Dan that the resin sets hard. There is no way i would do this type of joint live, its  a bit different than the kit the DNO uses.

Youd be quite surprised. Minus the armour bond it is pretty much the same for a service cable joint. On another note, that constant force spring is the same method how the earth screen is connected to on 11kv and 33kv cables.