Was hoping some of you outside plant guys could help with a problem. The tower side of our biz is currently in the process of replacing the building Lightening Protection system of a 13 story condo that was damaged by huricane Ivan. To make a long story short, they have been through numerous General Contrators and the place is a mess. What was left of the roof was demo'd and replaced with one of the rubber membrane type roofs. Problem is they have covered over the 6 downleads that go to ground with the rubber membranes. I have the fortunate task of going around with the roof man and letting him cut holes in the roof trying to find the original downleads. Now for the question, is there any type tool I could use to help me locate the downleads withought tearing up the enitre roof? We have one of those undergound type tracers we bought at an auction, but I tired it out on the ground ring of the tower here at our shop, and of course the fact that the cable is grounded is killing the Tone. I'm not well versed in the use of the tracer, and after months of trying to find a manual for the thing, I found it was'nt much help either. The only thing I can think of, is I am able to actually find where the downleads are tied to ground, dissconnect it from ground, then should be able to attach the "Toner" there. Any tips from you outside wire types would be greatly appreciated, I do not relish the thought of having them tear the roof to pieces. Man, this is how Ev must feels while posting.......might get used to this. Just trying to give as much info as possible. Thanks.

You guessed it...disconnect the lead where it goes to ground and place one lead to conductor and the other to the ground and go hunting for tone.

I was hoping I would'nt have to find the rods, I neglected to mention the building was built in 62, and is of poured concrete construction. As of yet, we have been unable to find the orgianl grounds, we do have a copy of the original plans, and the best we can tell is they were put in the concrete columns. The building has been remodled so much since 62 the plans bare only a slight resemblance to what we can acutally see and get access too. May have no other choice but to tear up the roof. If we can't find the originals, after making a few holes, we'll suggest running new downleads down the sides of the building.

If you can disconnect the cables thats the way to go. You may check if someone has copies of blueprints and locate them that way.

Telcomtex is correct. You want to isolate the end you are toning from, from grd. That is probably the biggest mistake most people make when locating cable. The other end your tracing too will have to go to ground to follow the line. Hope that all makes sense.

whoa, you guys are too quick for me. You have to get to one end of the cable or the other. If you can't find either end you're screwed. The only way to locate through induction is on power.

Here's an old farmer trick that Ditchwitch actually made into a cable locator with a swivel handle. We take two #10 bare wires, bend 4-5" down, leave 10-12" out horizontally, and very loosely hold the wires (sweaty hands help). When you walk over the best ground (like water) the wires will cross.

It's called "witching". And it works. And, no, I am not crazy, just ask Mitch.

:thumb:

KLD

"you're screwed" Story of my life.

That's what I figured, I was hoping that if by chance we did find one up top, I could hook the Tracer up to that one, and locate the rest. Was hoping for that magic bullet, but looks like I'm gonna have to use it to put myself out of my misery. Thanks for the information, guys.

Have you tried a good metal detector. A good one should be able to tell the difference from the roof and ground wire.

But, Reb, once you get one, a Dynatel locator with multiple freqs used in the inductive mode should let you have ALL grounds up there. Have you found a red iron attachment for the cathodic ground? Try it to the locator then to a ground rod. Sometimes it will act as a transmitter to other grounded cables. Or the MGN ground on the main power ground entrance to the locator to the ground rod. I'm thinking (boy, will that get me in trouble!) that you should get "flood" signals on all grounded cables. To get an exact reading you'll need to get between the ground and the ungrounded cable but this should give a "shadow" reading for a guestimate of the location.

Good luck.

KLD

Hmmm....have one in the closet from my relic hunting days....might be worth a shot.

I've seen others that could "witch" cable, but I never could. Might be worth a try.

Have to ask- why did they bury the cables under the roofing? Was that the way they were with the old roof? Didn't they think that maybe they should have consulted with you guys before doing this?

Sounds to me like the roofer and maybe the GC are responsible for this. And that sounds to me like you should be able to get any kind of locating gear that will work out of them since their only alternative is to remove the membrane and start over.

They should be kissing your ass! :bow:


-Hal

Like I said, this job is a mess. It's happened quite a bit, around here after Ivan. The original "contractor" was using unliscensed people...etc.etc. When I was there today for the meet, the new contractor who we have done these jobs for before, was in the process of tearing out the ceiling tiles because the previous guy had failed to get permits for anything and the City has shut them down. When I walked in the front door, I actually saw a 200lb chandelier's junction box mounted to a sheet metal duct. The enire weight of the chandelier was being supported by the duct. The new contractor is just having to fix all the screw ups at this point. I can almost understand them covering the downleads up, keep in mind the enire roof along with the old aierials was nearly blown all the way off, I'm sure there was not much of anything left for the roofers to cover up except for the stub throughs from the grounds going down. Add that to the "It's not my job" attitude and whala...here we are. We talked some more with the GC today and he agreed, we will try a few holes to find the old grounds, if no luck, will run new ones down the sides of the building.

Whenever a building owner replaces a roof with either a rubber or PVC membrane, they frequently want the warranty that goes with it (assuming a qualified roofing contractor). If this is the case, the roofing inspector (from Firestone, Carlisle, or whomever else) can be your ally. My neighbor is one of these guys, and I've heard horror stories of what he's made roofers do to do the job right. Hope my two cents helps a little.

The Greenlee tracer will work, it will provide tone even on a shorted to ground line. I have home builders that have used it to find buried ceiling heat ducts behind drywall, even though the ductwork is grounded. It will also work on live power as well, great unit, not cheap though. Here is a pic: https://www.newark.com/product-details/text/catalog/80184.html

Also/or, the cables are copper right? A good quality metal detector that can discriminate between types of metals should be able to find them.

Whenever a building owner replaces a roof with either a rubber or PVC membrane, they frequently want the warranty that goes with it (assuming a qualified roofing contractor). If this is the case, the roofing inspector (from Firestone, Carlisle, or whomever else) can be your ally.

I know exactly what you are saying, my wife with her former husband had a big commercial roofing company. I don't know if what you say is going to work in his favor. Cutting holes in a new roof and then patching is not exactly a good thing. It would be done by the authorized contractor which would mean that it should still be covered by the warranty, but unless you can keep it to a minimum it's not a good thing and the inspector from the manufacturer may not like it.

It would be a shame if you had to run new cables on the outside of the building. The existing ones are probably far superior than what you can expect from driven ground rods. They are probably connected to the footing ufer ground system.

Too bad that this whole job is so screwed up. I guess all you can do is do what has to be done, collect your money and don't look back.

-Hal

Not sure if it would work for you, but try your regular toner & wand. I've used it on a fishtape behind 2 layers of sheetrock and touching metal studs (grounded, of course) and it worked ok.

Since you're grasping at straws here, I've got a bit of an off the wall suggestion. When sweeping for eavesdropping devices we use a special probe to search for audio that is passing along pipe etc. It got me to thinking that maybe you could create that situation to your advantage. I took a transducer and placed a low frequency bass hum into a ground wire, then had one of the guys here take a shotgun mic and see if he could find it using it like a stethescope. He could actually hear it pretty well.

Keep in mind that the structure here was wood however. If it was a steel structure I imagine the hum would radiate everywhere.

I know it may be a long shot. It's just the kind of crazy thing I'd probably try if someone told me I couldn't do it. :idea: