cable junction underground

[canopy]

I have a cable of a type suitable for burial that is 4mm2, 3 core, not in conduit, buried 50cm underground. I would like to splice into this cable so it can go to an additional location. How can an underground T connection be made safely? Concerned about water intrusion.

[manfredtillmann]

in my humble opinion: if you feel you need to get instructions on how to go about this from an internet forum - you should not go about it at all.

don't you have an electritian in town?

[Crossy]

@Manfred. Do you really think a Thai domestic sparks would do anything other than bang a bit of tape round it? Even the MEA / PEA don't use underground cables in any great numbers so the experience and (probably) the equipment just isn't here.

@Canopy. Is there any way to keep the splice above ground? It's far easier to keep water out of a box a few inches above the surface.

Failing that the (not really preferable) method would be crimped butt splices overlaid with adhesive-loaded heatshrink tube on each core. Followed by an overall cover of bigger adhesive-loaded heatshrink and possibly an overlay of self-amalgamating jointer's tape.

[Daffy D]

Back in the day when I was working in the field our electrician used a special kit to make a water proof joint for an underground cable.

As far as I recall the kit consisted of a mold that held the part of cable with the joint and this was filled with some sort of resin to encapsulate the joint and seal it from the elements.

Don't expect a professional kit like that would be readily available but I was thinking that a fiberglass kit might work just as well.

Wrap the joint in several layers of fiberglass matting then coat it liberally with resin.

Could even lay the joint section in a plastic container filled with resin to give it extra protection.

[BobTH]

Back in the day when I was working in the field our electrician used a special kit to make a water proof joint for an underground cable.

As far as I recall the kit consisted of a mold that held the part of cable with the joint and this was filled with some sort of resin to encapsulate the joint and seal it from the elements.

Don't expect a professional kit like that would be readily available but I was thinking that a fiberglass kit might work just as well.

Wrap the joint in several layers of fiberglass matting then coat it liberally with resin.

Could even lay the joint section in a plastic container filled with resin to give it extra protection.

Agree with Daffy D, I used to do underground electrical splices also. 3M makes them and I would think such a large company would also have them available here in Thailand or at least a reasonable copy of, at an electrical supply shop. The kit I used was called 90-B1 3M Electrical Splice Kits. It has a plastic mold that fits over your connection and comes with a two part epoxy resin that you mix in a two part bag by pulling the seam which allows the two parts to co-mingle. The plastic mold has a small capped hole in it and a small funnel to insert the mixed epoxy. There are a few different configurations they sell depending on your needs.

Additionally for your initial cable connection prior to the epoxy mold, you should look for a split bolt, brass would be ideal but I think other metals would work fine because it will end up sealed by the splice kit and no moisture can contact it.

[phoneguy702]

medium voltage and high voltage splicing is a craft, Scotchkote is one manufacturer. but I would not suggest that an untrained person undertake this kind of splice.

[Thorgal]

Waterproof T-connectors are available on most online shops like Ebay, etc... Costs around 6GBP.

Will be hard to find a IP68 in a local Thai shop.

[manfredtillmann]

i stand by my original post and disagree with all suggestions made here so far.

for starters one NEVER places a cable underground without the minimum protection of a high density pvc conduit.

there is no permanently waterproof joining method for high voltage electrical cable, sooner or later all these joints will suffer water ingress and failure.

the only acceptable method is placing a pit similar to the one in the photo, preferably with its own drainage plumbing, and elevating the as 'waterproof as possible' cable joint inside above possible flood levels.

and if i could not find an electrician do do at least the cable joint for me in a professional manner - than the job would remain undone.

the second photo is a pix of the back of my truck - just to give some credit to my exploits.

[Crossy]

i stand by my original post and disagree with all suggestions made here so far.

Even the Post #3 suggestion of moving the splice above ground?

I too wouldn't bury a soft cable with zero protection, but there are plenty of cables rated for direct burial with no conduit and if it's deep enough to be safe from normal gardening activities then the risk is small.

I agree that almost any underground splice will eventually leak. But this is almost certainly a domestic situation (4mm² cable) with RCD protection for the cable, so if / when the joint does fail the RCD will trip and our OP will be ruing the day he buried a joint.

[billphillips]

I assume that as the cable is not in a conduit that it must be a temporary arrangement. Consider the possibility of running two separate supplies in conduit to the areas that you need to supply from the distribution board and protected with rccb's. If temporary, waterproof splices can be made using amalgamating tape. The problem is more to do with bugs, rodents and soil disturbance causing a problem with the unprotected cable and join.

[manfredtillmann]

i stand by my original post and disagree with all suggestions made here so far.

Even the Post #3 suggestion of moving the splice above ground?

I too wouldn't bury a soft cable with zero protection, but there are plenty of cables rated for direct burial with no conduit and if it's deep enough to be safe from normal gardening activities then the risk is small.

I agree that almost any underground splice will eventually leak. But this is almost certainly a domestic situation (4mm² cable) with RCD protection for the cable, so if / when the joint does fail the RCD will trip and our OP will be ruing the day he buried a joint.

the place i live in has neither earth cabling nor - obviously - rcd's. perhaps my miss - assumption was that these things do not exist in thailand.

irrespective, to place your life in the 'hands' of an rcd is like playing russian roulet.

i have never heard of a cable rated for 'direct burial with no conduit', there is above ground cable and under ground cable but - to my limited knowledge - ALL cabling in ALL situations is to be shielded by conduit, to make things safe.

yes, i know, my place does not comply with that, either.

let's take it this way: my advice was based on what i believe is the right thing to do, not what you can get away with.

i would hate to one day get a letter from a lawyer claiming i caused the death of someone due to a 'she'll be right' post i made on this forum.

over and out.

[Crossy]

i have never heard of a cable rated for 'direct burial with no conduit', there is above ground cable and under ground cable but - to my limited knowledge - ALL cabling in ALL situations is to be shielded by conduit, to make things safe.

yes, i know, my place does not comply with that, either.

Here you go http://www.bangkokcable.com/product/backoffice/file_upload/131007_34-450!750V%2070C%20NYY-2C.pdf

Or any of these http://www.bangkokcable.com/product/category1

Put it in with a mole-plough and you don't even need to dig a trench http://www.hmcplantservices.co.uk/ploughing.html

Our OP probably has NYY (which is available in smaller sizes than Bangkok Cable do) as that's by far the most common BUT placing a joint of any type directly in the ground is definitely in the "not recommended" category.

[manfredtillmann]

i have never heard of a cable rated for 'direct burial with no conduit', there is above ground cable and under ground cable but - to my limited knowledge - ALL cabling in ALL situations is to be shielded by conduit, to make things safe.

yes, i know, my place does not comply with that, either.

Here you go http://www.bangkokcable.com/product/backoffice/file_upload/131007_34-450!750V%2070C%20NYY-2C.pdf

Or any of these http://www.bangkokcable.com/product/category1

Put it in with a mole-plough and you don't even need to dig a trench http://www.hmcplantservices.co.uk/ploughing.html

Our OP probably has NYY (which is available in smaller sizes than Bangkok Cable do) as that's by far the most common BUT placing a joint of any type directly in the ground is definitely in the "not recommended" category.

http://www.hmcplantservices.co.uk/ploughing.html

these machines are the very tools that let you dig through any service without the slightest indication that it is going to happen. good for virgin, open country, but poison for developed areas.

as for the cable links....

there are obviously different standards for thailand than there are for countries that value their citizens lifes.

lets just finish on this, ok?

[Crossy]

lets just finish on this, ok?

OK.

But do note that both NYY and SWA are available in the UK and permitted for direct burial, so we're not looking at just Thailand (and the UK is right up there with the biggest nanny-states).

https://www.tlc-direct.co.uk/Main_Index/Cable_Index/NYY/index.html

https://www.tlc-direct.co.uk/Products/SW4slash2.html

It is always my aim to educate that there isn't just one way to do a job, nor is there just one set of standards.

It's also worth looking at this PEA document for an overview of the Thai domestic regulations, MEN (PME) connections, grounds and RCDs are required for new installations. http://crossy.co.uk/Handy%20Files/groundwire.pdf

Agree on the mole-plough observation.

EDIT By the way, for my own education, I'm intrigued where permits underground electrical cabling in yellow conduit (the [almost] universal colour for natural gas)? Thailand uses black HDPE (not PVC) with a red stripe.

[manfredtillmann]

lets just finish on this, ok?

OK.

But do note that both NYY and SWA are available in the UK and permitted for direct burial, so we're not looking at just Thailand (and the UK is right up there with the biggest nanny-states).

https://www.tlc-direct.co.uk/Main_Index/Cable_Index/NYY/index.html

https://www.tlc-direct.co.uk/Products/SW4slash2.html

It is always my aim to educate that there isn't just one way to do a job, nor is there just one set of standards.

It's also worth looking at this PEA document for an overview of the Thai domestic regulations, MEN (PME) connections, grounds and RCDs are required for new installations. http://crossy.co.uk/Handy%20Files/groundwire.pdf

Agree on the mole-plough observation.

EDIT By the way, for my own education, I'm intrigued where permits underground electrical cabling in yellow conduit (the [almost] universal colour for natural gas)? Thailand uses black HDPE (not PVC) with a red stripe.

not so in oz!

different countries, different standards (WHY???)

underground power conduit in oz are orange (is that not what my photos show?) and above grey.

underground data conduit in oz is white - and same above.

required depth is 500mm COVER, so if you place a 100mm conduit (fiber optics or +64mm2 multi power ) your min. trenching depth is 600mm. rule of thumb - thats what you dig to - every time.

backfill to half depth, than place 'warning - tape' (orange - power, white - data, yellow - gas, green - potable water, purple - recycled water etc., matches conduit / pipe colour), backfill and compact to finish.

and i do think that australia will easily win the title of 'the biggest nanny country' , powered by it's outrageous litigation laws. but that's for another forum topic to deal with. without me.

be good, cheers, mt

[manfredtillmann]

http://crossy.co.uk/Handy%20Files/groundwire.pdf

forgot to comment:

up here in the far north east rules and regulations mean very little, especially if the owner of your rental home is a top big - wig.

you can pm me if you'd like to visit - it's the nearest to time travel you will ever experience.

[canopy]

Building standards are a set of minimums. Meeting the standard can be like earning a grade C on a scale of A-F. Typically if you meet all the standards you will have something decent. But if you want real high quality then you need to exceed standards--go above and beyond. On high voltage electrical situations that is worthy of consideration.

[Deke]

EDIT By the way, for my own education, I'm intrigued where permits underground electrical cabling in yellow conduit (the [almost] universal colour for natural gas)? Thailand uses black HDPE (not PVC) with a red stripe.

Thailand also uses the yellow PVC for electrical and telephone installations. Here's one local manufacturer.

[blackcab]

I know it's been said but in the UK the supply cables from the electricity distribution company are not buried in conduit.

I know because for some reason my father has a cable joint under his rose bush in his front garden. Something went wrong and the electricity company had to repair the joint, which meant digging up his garden.

He was not happy.

[Crossy]

Thailand also uses the yellow PVC for electrical and telephone installations. Here's one local manufacturer.

The keyword here is "underground", I'm fully aware of the yellow stuff used indoors

@Manfred, yeah, looking at the picture of your truck the conduit is definitely orange (which would be telecoms in the UK), I'd not made the connection with Oz (your 'she'll be right' comment should have given me a clue)

For interest, UK underground duct colours (black HDPE with a trace of the appropriate colour is accepted practice):-

For comparison, Table 1 of this document has the Aussie colours http://www.pipa.com.au/sites/default/files/document/attachment/pop203.pdf

[Bill3173]

To the op's problem. Trenches, depending on soil type and elevation can become underground waterways, so you have to assume any cable / joint will be sitting in water. I would not recommend you do an underground slice /joint, as it would require one of the following.

1/ A specialist splice / joint kit, of which I have never seen one suitable for 4mm, even if one is made, I doubt you could source one in Thailand.

2/ Crimp and heat shrink method (which there are several methods) but would not advise it, if you haven't done it before.

3/ Improvised joints / enclosures which include amalgamating tape, mastic, modified junction boxes, etc. They will fail, believe me, as I I have seen many failed joints (so don't let your local electrician talk you into it).

As to recommendations, not enough info' is given (cable run, trench distances etc)

General info'. Previously in Australia I was employed at network level as a LV underground tester which included fault finding and rectification, later as a work supervisor which included organising authorisation, permits, switching, audits, etc for the underground cable work parties.

Direct buried cables and joints (including HV) is used extensively in Australia, but this is done at a network level not private (customer). It is considered quite safe if done correctly and by trained personnel. Manfreds posts are (as far as I am aware) correct for private assets, but would fail audit at a network level. There are reasons why direct buried is considered safe at network level but not private (too many reasons to list here).

[canopy]

I found a number of Thai web sites advertising the 3M splice kits for underground junctions like here. Baffling because when asked every one of them so far says they don't have anything like this. Anyone know where one might find these types of products?

[Led Lolly Yellow Lolly]

I've not read every post, so sorry for any repetition, I just want to get ot the point. . . . .

I can confirm 3M resin splicing kits are available in Thailand, I've ordered them and used them before.

Regarding your cable, if it's not Steel Wire Armoured cable, it is NOT suitable for direct burial. The way I did it with my houses, so far four times, was to use 16 mm NYY cable, 25 mm in one case actually. I fed this through HDPE conduit (High Density Polyethylene) buried 60 cm underground. Before backfilling with soil, we poured 5 inches on concrete around it.

I expect this arrangement to last at least three times as long as the house, as long as the cable is never overloaded.

[canopy]

Was a little hard to find, but I can now recommend charn-chai.com which has 3M resin splice kits in stock and has great delivery service.

[Pacificperson]

The 3M kits are what we use with the cables for the submersible pumps in our salt water wells (460V, 3-phase). If they hold up in full strength salt water, they should hold up underground.