Conduit Locate

[Edrick]

To the guys who do installs if you walk into a location that has no as builts or even design plans what do you find to be the best method to locate the path of a conduit run. For example to find where there might be pull boxes or breakouts.

Any tricks you have, trying to find some stuff in a concrete slab

[cpf]

Oooh I want to know this too, maybe I could finally solve the mystery of the 5 XLR jacks...

[Edrick]

I'm thinking maybe some type of snake with a tracker on the end that you could use a wand to walk around and locate.

[Clarkwg3]

I'm thinking maybe some type of snake with a tracker on the end that you could use a wand to walk around and locate.

That gave me an IDEA!!

I have a cable tracer for use on dead conductive but not 'live' cables. Got it at Farm & Fleet for around $40.00. I use it most on cat 5 cables to find which one, then used my tester to test the cable. In the past I've tracked a cable buried under 6" of earth. The tracker 'sending' unit has a pair of aligator clamp leads to connect to just about anything metallic. Could easily attach to the male end of a mic cable/snake.

[Edrick]

I have those but depending on the cable and material it's coveted in doesn't always work too well

[Clarkwg3]

The next step up I know of is what utility companies use to locate buried lines. Now your talking the $500+ area.

[Edrick]

That's not a problem if it was to actually work to locate the path of a conduit or audio cable reliably

[Clarkwg3]

I'll check with City Engineers Monday about the make/model they use. Just how reliable R they? A 4inch pvc gas line is buried with a 12AWG wire aginst the pipe. I've been present when 'Diggers Hot Line' surveyed this site. He was able to 'off the record' tell me in this spot the wire was 7 foot down. Once we dug, the wire was 7 foot down (on top of the pipe) and directly below the mark.

HOLY MANURE!!! I was way off on the price range for what I was thinking of. Sorry for getting your hopes in range up.

Grainger has the model avaliable:
http://www.grainger.com/Grainger/LEI...CX4?Pid=search

Underground Service Locator, With Depth Estimator, Length 30 In, Width 10 In, Height 3 1/2 In, Power Source 6 AA Alkaline Batteries, Transmitter Frequency Power Mode 50/60 Hz, Radio Mode 15-30 Hz, Generator Mode 8 and 33 KHz, Location of Underground Utility Services, Includes Batterie

List price: $1175.00

[Edrick]

Usually in that case they have a tracer wire. I don't know if there's a requirement would a 22gauge wire be fine, the next issue becomes if you don't know where the wire ends do you have to disconnect it

[SteveB]

a location that has no as builts or even design plans

Note that neither "as builts" nor the original design plans typically show the actual path the conduits will take from point to point. It's up to the EC to find a route, though sometimes when it's critical, the electrical engineer might indicate a particular path to avoid conflicts, etc... Thus if you need to find the actual conduit, you just need to locate and follow visually. If buried in building concrete, it's anybodies guess. Trace kits typically get used when you are trying to find out which outlets and fixtures ended up in what circuit panel, if there's no other paperwork showing this.

[teqniqal]

The actual run may be a little more difficult to determine, but if your are trying to find-out where it ends-up, or maybe any intermediate junction boxes, here are two suggestions:
1. Use a small air horn (party horn) and place the horn bell as close to the conduit entry as possible, maybe even use some putty to seal the joint, then when the building is quiet: toot the horn in short bursts while you have other helpers listen for the sound. It may take awhile, but you can usually find it.

2. Use a smoke generator and make a nozzle adapter so you can pump it into the conduit. Look around for where the smoke comes out. If you can color the smoke, that helps, too, as white smoke is difficult to see. Also, adding an aroma to the smoke can help, too. An old electrician's trick is to blow cigar smoke into a conduit. You can't see it, but you sure can smell it.

3. DON'T use water or other liquids. Conduit comes in abut 10' sticks, so liquids just seep out of the joints. If this is above a sheet-rock ceiling, well . . . . you get a mess.

To double-check you have the right conduit, count the number and type of cables entering each endpoint. If they are close, but maybe missing a few wires, then there is probably another intermediate junction box you have not yet found.

Metal detectors can sometimes be helpful, but they don't work for PVC conduit in a floor slab.

On a more serious note - court cases have upheld that contractors can be held liable for producing inaccurate as-built documents. One case I know about was where a worker cut into a wall that showed on the as-built plans to be 'empty' and instead, cut through a power conduit which killed the worker. If you are cutting into conduits, kill the building power if you don't know what's in them!

From a VERY personal experience, don't go poking a metal fish tape down an empty conduit to see where it goes. I ran one into a hot electrical panel and killed the power to the whole building. Fortunately for me, the 400 Amp service grounded to the conduit and blew the circuit breaker before I was fried. I was left stuck in a dark crawl space waiting for someone to get the power back on so I could extricate myself. They showed me the melted fish tape in the breaker box and I just about fainted. USE NON-METALLIC FISH TAPES!

[museav]

There are many other options but for tracking down audio wires a tone generator and inductive amp like Fox and Hound Series are very common.

Tracing conduit with a puff ball/blower or with fish tape can be difficult and/or misleading if you have things like intermediate boxes with multiple conduits entering and/or leaving them, so in such cases it is usually best to try to track each segment of the run independently rather than to try to track an entire run through multiple pull and/or junction boxes.

AutoCAD type infrastructure drawings typically do not identify specific locations or the details of the routing of conduit, however Revit style BIM drawings essentially require inserting and routing the actual boxes and conduit, not that how they are drawn is necessarily how they get installed.

[derekleffew]

From a VERY personal experience, don't go poking a metal fish tape down an empty conduit to see where it goes. ... USE NON-METALLIC FISH TAPES!

Article from EC&M discussing this very topic: Electrical Forensics: The Case of the Fish Tape Fiasco .