Help! Residential underground splice failed

[Hv&Lv]

I have a Dyana that in using just the RF in tracing mode hooking up to the lost conductor will drop the signal off about 6" when I pass the bad section and if I mark it where I loose the signal, then turn around and trace it back from the other direction again it will drop off about 6" past the break, mark and directly between these two marks is the break, but why when I have the fault locater attachment for the Dyna? it hits it dead on.

I have a Dynatel earth return fault locator and cable locator also. (model 573A) IMO the best fault locating machine ever for finding secondary faults with the A frame.
Not much good for finding primary faults in 35 kV cable. These don't fault to earth, they blow out with a tiny pinhole to the concentric neutral they will have an open gap about 3/8" between primary and neutral. Need a good size DC pulse to jump the gap, then listen for the thump. Ours was $3K in 1994.
The 2273 is an excellent machine. I hate that they took the analog meter off and went totally digital with that machine. We have one of those also for the other office. I won't give up the 573.

You ever use yours for finding power lines at the 60 HZ scale and no transmitter?

 

[hurk27]

I have a Dynatel earth return fault locator and cable locator also. (model 573A) IMO the best fault locating machine ever for finding secondary faults with the A frame.
Not much good for finding primary faults in 35 kV cable. These don't fault to earth, they blow out with a tiny pinhole to the concentric neutral they will have an open gap about 3/8" between primary and neutral. Need a good size DC pulse to jump the gap, then listen for the thump. Ours was $3K in 1994.
The 2273 is an excellent machine. I hate that they took the analog meter off and went totally digital with that machine. We have one of those also for the other office. I won't give up the 573.

You ever use yours for finding power lines at the 60 HZ scale and no transmitter?

All the time, it will follow primaries and secondaries, as well as branch circuits, the range gain has a pretty good gain adjustment to get to the really deep conductors, and in RF mode tracing you can put a separate 12 volt battery on the transmitter to do 5 watts input, and it can trace really deep and for a long ways, it will tell me the depth and is within an inch every time, it does about all you would ever need, although it is all digital it has a bar graph to mimic an analog and works great in centering mode to pin point the wire, pipe, or what ever you are tracing, I use 8khz the most but in some very wet conductive soils the 200khz works better but doesn't have the range and falls off much faster.

 

[newservice]

Thanks all, starting 830 tomorrow, my brothers running the machine Ill find out more about it, but he swears its darn good.

FYI this 200A ug service has a disconnect from the poco located ug at the curbside, just a box with taps. From there it goes up one side the driveway, and crosses it. After it crosses is where we made the original splices in order to move it so they could build another car onto the garage. It ended up that after they did the footer and foundation and built the garage, the electric trench ws pretty close to the structure, so am thinking they nailed it with something backhoe idk. Will know tomorrow and let you know.

 

[newservice]

RESOLVED> PROBLEM FOUND TODAY

RESOLVED> PROBLEM FOUND TODAY

My brother showed up with his Tecktronics TDR and found a fault 11.4 feet from the meter channel, basically in the loop under the meter, GC was pushing me to replace the whole UG line from the old splice to the meter, he wanted an ug box to rise up right next to the front walk and driveway of the house, wanted to put it all in pipe, said hed pay for it. I finally said to him I am the electrician here and even if I only assist you, Ill be the one owning this job; the fault is oin cable that I did not even touch, and I wouldnt do this job your way anyway, and im not obligated to give you an upgrade from what I did. . He finally backed down, backhoe guy dug up at the meter and lo and behold I was looking at the loop of triplex and there, I though I was looking at a big splotch of pigeon poop, but it was about a 3 inch section of the CC conductor ripped into by probly the backhoe when they came into that corner with the footer. Picked it up and the cc fell in two pieces. Unbloted the Illco direct burial splice, it was pristine inside, nothing but shiny aluminum and Replaced 12' of 4/0, crimped on a new lug in the meter and walked away with the inspector en route. Oh, and left him the bill.

So my brother told me what the parameters were for voc(?) and the make and model of the Tectronix scope, but I think it said Cable Fault locator on the front by the LCD screen. I'll have to check back with him again to know what that all is for sure. He did have a little trouble at first because the break was so close to the test probe, 12', he said 'it threw me'. But he knows his stuff and buckled down and got it. I could just see all the wind fall from the GCs sails from that point on, he knew I we him dead nuts. All the inground splices looked fine.

 

[ptonsparky]

:thumbsup:

 

[readydave8]

Glad you were right, I know how good that feels!

 

[Hv&Lv]

I hate to say it like this, but it sure does feel good to prove an overbearing GC wrong.:thumbsup: Glad it wasn't the splices. You tack on an extra fee because he doubted your work? Would like to know the model # of TDR he has. Still curious about the V_P.
I have to ask this, your brother charged you for this? Or you threw the fee to the GC?

 

[newservice]

I hate to say it like this, but it sure does feel good to prove an overbearing GC wrong.:thumbsup: Glad it wasn't the splices. You tack on an extra fee because he doubted your work? Would like to know the model # of TDR he has. Still curious about the V_P.
I have to ask this, your brother charged you for this? Or you threw the fee to the GC?

In my 15 years being licensed this was the first job that had come back so I just wanted to get out of it. Also the GC was not really a bad guy just a bit ..well...GC ish and frankly I think hes a bit green. Threw the guy my labor for free, just hit him for the $100 my brother charged (cash or gold bullion he said) as he is very good and the tectronix is company owned and he did it with the blessing of the business owner. Best 1oo I spent this year IMO. Was very satisfying to find and fix it so easily.

 

[newservice]

few pics of the failed cable

few pics of the failed cable

Couple shots in the hole still others in my back yard..can see the big white spot where the Al blew out, looks like a huge old nick from the backhoe. Esisting meter was right by the new excavation.

 

[newservice]

I would bet it wasn't a failed splice. I suspect the cable was hit somewhere else. Good luck. Perhaps you can find someone with a cable locator.

Right on both counts. See posts ~ 44-48

 

[kwired]

I hate to say it like this, but it sure does feel good to prove an overbearing GC wrong.:thumbsup: Glad it wasn't the splices. You tack on an extra fee because he doubted your work? Would like to know the model # of TDR he has. Still curious about the V_P.
I have to ask this, your brother charged you for this? Or you threw the fee to the GC?

It is great to prove these accusing guys wrong. Had one totally chew me out for not putting a receptacle for a range hood/microwave one time. I carefully measured and drilled a hole in back of cabinet where I thought it should be. Told him to come look --- he really did not have anything to say- not even an apology:roll:

Couple shots in the hole still others in my back yard..can see the big white spot where the Al blew out, looks like a huge old nick from the backhoe. Esisting meter was right by the new excavation.

Hard to tell from picture if it was damaged by backhoe, is obvious the insulation was compromised in some way. The white stuff is aluminum oxide - this is what happens when aluminum oxidizes, and is always much more deteriorating when underground aluminum has compromised insulation vs the thin film that develops in above ground situations.

 

[newservice]

Yeah it is hard to tell if was a backhoe, could have just been a rock in the pit. Another thing I wonder about is that the fact that our poco requires a loop or an S loop at the bottom of the meter in the ground whether or not you use pvc. So you have exposed cable, and when you loop it you stretch the insulation and put tensile pull on it, making it ripe to break open if nicked. If that trench isnt pristine, all the rocks out of the bottom, sides, even the little nubs that may be sticking out, you're primed for a nick. You want that bed fit for Queen Elizabeth to lay on. That said, this was the first time I ever did a job like this where the foundation trench was put in AFTER the electric trench, again primed for a nick by any number of subsequent disturbances during the construction.

 

[hurk27]

Yeah it is hard to tell if was a backhoe, could have just been a rock in the pit. Another thing I wonder about is that the fact that our poco requires a loop or an S loop at the bottom of the meter in the ground whether or not you use pvc. So you have exposed cable, and when you loop it you stretch the insulation and put tensile pull on it, making it ripe to break open if nicked. If that trench isn't pristine, all the rocks out of the bottom, sides, even the little nubs that may be sticking out, you're primed for a nick. You want that bed fit for Queen Elizabeth to lay on. That said, this was the first time I ever did a job like this where the foundation trench was put in AFTER the electric trench, again primed for a nick by any number of subsequent disturbances during the construction.

Personally I stay away from any concrete work as to many chances of wire damage, form stakes are a biggie that can get you, and even hand shovels unless you are much deeper, I have run conductors down a drive but stay away from the edges as this is where you get hit by form stakes, the only problems with being under the concrete is not being able to fix it if it does get damaged, and they can form off half of the poor and if they don't know where the wire is can drive a form stake right into it.

 

[ptonsparky]

You discovered one of the rules when repairing or splicing existing underground. Always meg it before splicing or covering. Always. Locate. Dig. Cut. Meg. Repeat as needed before splicing even the first time.

 

[ActionDave]

You discovered one of the rules when repairing or splicing existing underground. Always meg it before splicing or covering. Always. Locate. Dig. Cut. Meg. Repeat as needed before splicing even the first time.

You must work on irrigation pivots.

 

[ptonsparky]

You must work on irrigation pivots.

:lol::thumbsup: How did you guess?

 

[ActionDave]

:lol::thumbsup: How did you guess?

Been down that road, or to use a better metaphor, out in that field more than once. One of the best investments my boss made was a fault finder. It's now an annual rite of spring to track down wires chewed on by gophers. Implementing the procedure you described was learned the hard way, but sure saves on embarrassing call backs.

Have a repeat customer that, if I live long enough, is going to have the whole feed changed over from RHH to butt splices and shrink sleeve.

 

[kwired]

Personally I stay away from any concrete work as to many chances of wire damage, form stakes are a biggie that can get you, and even hand shovels unless you are much deeper, I have run conductors down a drive but stay away from the edges as this is where you get hit by form stakes, the only problems with being under the concrete is not being able to fix it if it does get damaged, and they can form off half of the poor and if they don't know where the wire is can drive a form stake right into it.

I can understand footings, but most other concrete work you should be buried deep enough that form stakes are not going to be a problem, or do you have guys that use really long form stakes? Table 300.5 does not go less than 18 inches for direct buried cables or conductors except for under a building but notes it must be in raceway or type MC or MI cable designed for direct burial.