Underground Cable Detection - Locating old cables

patsy_mccabe

Maybe someone can shed some light on this.

I have a lot of underground electrical cables running from the home house here to 2 farm sheds. I want to find the location of one of these cables to connect up an existing water well to supply the farm. I hired out an underground cable detector, a "Leica DD120".

Now, I can find all the more recent cables, even in some places where they are under concrete. The one older cable, that I'm looking for, is proving impossible to detect. It's maybe 50 years old and someone suggested that maybe it has lead wire surrounded the inner wires. Could this be the reason?

The wire is really stiff to bend. Even when I move the detector around where I see the cable coming up from the ground - no beeps.

Also, the electrician who replaced the electrical box in the shed, bonded the outer wires to ground. Could this be the reason?

By the way, I had the radio on in the shed during all this, so deffo current in the cable.

10-10-20

https://www.boards.ie/discussion/2058347981/underground-cable-detection-locating-old-cables

Hi! I'd be wondering if a radio may not pull sufficient current to generate sufficient noise for the cable to be picked up; try something more powerful such as a 500w lamp or a drill left running. The other point which you brought up is shielding - if that cable is shielded using steel or even lead or such, then the signal off the live and neutral will be reduced and mightn't be seen. If it's a shielding problem then you can use the shielding as a transmitter - have a look at p35 on the manual and you'll see that there is a transmitter that you can connect directly to the shielding and then to earth which makes it ping.

https://shop.leica-geosystems.com/sites/default/files/2023-11/976157_Leica_DD120_DD130_DD175_Series_Locators_and_Accessories_UM_V.3-0-0_en.pdf

Plus don't forget that this one cable could be buried deeper than the rest of them and mightn't be as easy to find.

patsy_mccabe

Found the old cable today. Found it where, there was a faint beep with the detector. It's running through a neighbours site and comes back into our place again. At least I know where it is now so can tap into it.

patsy_mccabe

Just for the record, this cable was in fact protected with an inner surround of lead.