buried swa fault

[gaffer]

Hi all hope someone can point me in the right direction,
On one of my jobs I have a detatched garage fed from the main house by a buried 16mm 2core swa,now I have been splitting the garage ccts from the flat ccts above .
When I switched the supply back on the mcb in the house tripped.I had already tested everything I had worked on so I knew that was alright.So I turned my attention to the submain discovered that I had a direct live to earth.
Heres the question,how do I discover where the fault is on the cable?,I assume this will be done by measurement of resistance from either end ?
Any advice would be appreciated.
Gaffer.

 

[ian.settle1]

Hi all hope someone can point me in the right direction,
On one of my jobs I have a detatched garage fed from the main house by a buried 16mm 2core swa,now I have been splitting the garage ccts from the flat ccts above .
When I switched the supply back on the mcb in the house tripped.I had already tested everything I had worked on so I knew that was alright.So I turned my attention to the submain discovered that I had a direct live to earth.
Heres the question,how do I discover where the fault is on the cable?,I assume this will be done by measurement of resistance from either end ?
Any advice would be appreciated.
Gaffer.

Was everything working OK before you started the work.

What is the distance from house to garage?

If it is not far would be cheaper to run in a new cable than trying to find the fault.

 

[gaffer]

Hi Ian,
Just got back from job,just found it was tripping out before I did anything (customer was trying to blame me)anyway, the gardner told me today that drainage company did some work at the front of the house in March.Borrowed a cable detector and cable goes right up close to manhole where they worked.So going back tomorrow with my spade and camera.

 

[lockhes]

Hi Ian,
Just got back from job,just found it was tripping out before I did anything (customer was trying to blame me)anyway, the gardner told me today that drainage company did some work at the front of the house in March.Borrowed a cable detector and cable goes right up close to manhole where they worked.So going back tomorrow with my spade and camera.

hate it when people try blame you for things what were there or wasnt working before you tpuched anything

 

[azza]

Hi all hope someone can point me in the right direction,
On one of my jobs I have a detatched garage fed from the main house by a buried 16mm 2core swa,now I have been splitting the garage ccts from the flat ccts above .
When I switched the supply back on the mcb in the house tripped.I had already tested everything I had worked on so I knew that was alright.So I turned my attention to the submain discovered that I had a direct live to earth.
Heres the question,how do I discover where the fault is on the cable?,I assume this will be done by measurement of resistance from either end ?
Any advice would be appreciated.
Gaffer.

even with everything disconnected from the garage does the MCB still trip? not Knowing the installation there could be alsorts of joints/connections buried! as someone else said may be easier to re run the supply to the garage or before you start diggging the trench temporarily intall an appropriate size cable from CCU to the garge to to eliminate possible faults

 

[mechelec]

you need one of these. I use one all the time when fault locating on underground cables.

Megger - TDR1000/2 (CFL510F TDR-US Market)=

 

[gaffer]

Hi all,
split the cable halfway ,which was just by manhole but no obvious damage.The damaged bit is under about 8 meters of brickpaving ,so massive expense to replace and the customer was not happy.
Got chatting to the drainage guy,and he offered to mole under brickpaving for me.Met him on site on friday afternoon,and what a brilliant bit of kit he had.All we did was dig two holes either side and he connected the mole to a compressor and off it went.600mm underground to the other hole,tied new submain on and pulled it back.Took about an hour ,but saved a fortune.
Customer is well happy now.Never seen one of these moles in action before,but would consider using it again.Guy said it can only go about 15 meters before digging another hole ,but ideal for going under drives etc.
Only problem I can see is you cant put caution tape above cable ,although I did wrap the submain in some.

 

[tigerpaul]

What would happen if you put the mole underground and inadvertently set it off in the direction of an existing underground SWA? Would the mole cut in in half?

I've no idea what this mole thing is you're on about but it sounds useful anyway? Can you get them from the hire shop?

I have to run an underground SWA in from a house to a garage soon, the route I need to take is below the concrete drive. The customer wants to cut a trench to lay the cable in, he's only thinking about a little 6 inch deep trench, but I reckon the cable should be buried a lot deeeper than that.

Maybe your mole would come in handy?? Then we could dig 2 much deeper holes and then leave the concrete drive mostly alone.

What diameter hole does the mole bore?

 

[gaffer]

Hi tigerpaul,
The guy told me if the mole hit a drain if would smash its way through,even a concrete one.So you have to be carefull.It runs off one of those compressors that the road gangs use so its pretty powerful.It bores a hole 50mm in diameter.You might be able to hire one,Im in the Channel Islands and as far as I know there is only two companies over here that do it,and they insist on doing the job for you.google it see what you come up with.

Sorry try mole engineering in google