Any tricks to find wires (in conduit) in ceiling?

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Old 05-17-19, 04:49 AM
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Any tricks to find wires (in conduit) in ceiling?

Are there any tricks to detect wires in conduit in ceiling?

A simple "live wire probe" will not work.
Stud detectors seem to have a hard time, plus it is difficult to distinguish trusses, conduit, brackets,...

Are there any tricks of the trade or tools?
 
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Old 05-17-19, 07:54 AM
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Check out Walabot. It is a device that works with smart phone and can distinguish the type of material being sensed (wood, metal, wire, etc.)
 
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Old 05-17-19, 10:57 AM
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The device below consists of a transmitter and receiver, and although it costs $200 I thought it was well worth it considering what you get.

https://www.amazon.com/gp/aw/d/B01N9ZHW3K/ref=ppx_yo_mob_b_inactive_ship_o0_img?ie=UTF8&psc=1

You hook the transmitter (Tx) somewhere along the metal conduit, pipe, etc. and it applies a test signal that you can sense with the probe on the receiver (Rx) unit.
There are two basic ways you can use this. One way you connect the red clamp of the Tx on the object, and the black clamp on whatever ground reference is convenient (metal plumbing, etc.). So the Tx basically applies a test signal voltage to the object and the probe on the Rx picks up the signal by capacitive coupling. This works well if the object is electrically floating, but not as well with something that's grounded like a conduit is at the breaker box (it tends to short out the applied test signal).

But what sets this device apart is you can use it in what I would call an inductive sensing mode, where with a long piece of wire you connect one end of the conduit, pipe, etc. to the red clamp of the Tx and then the black clamp to the other end. This sends a test signal current along the conduit/pipe between the 2 points where you made the connections and so it creates a magnetic field near this section of the conduit. Then the Rx probe can pick up the signal from this particular section of conduit/pipe but not confuse it with a different/conduit pipe that might, for example, be a foot away (even if these two conduits are eventually connected together or grounded some distance away such as at the breaker box. I found this very useful. This measurement technique was not explained very well in the manual but fortunately as an electrical engineer I was able to realize what needed to be done (i.e. complete a closed circuit that includes the Tx unit, the section of conduit to be detected, and a large loop of wire moved well away from the object being measured).
So, for example, if you wanted to detect the conduit going between a switch box and a light fixture box, you would connect the Tx unit across the ends of the conduit at these locations (using a long piece of wire to extend the Tx lead).
 
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Old 05-17-19, 04:45 PM
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I don't know if the Walabot will work above plywood ceiling and stud/trusses.

The Wire tracer seems to be a good option, just a bit pricey. Wonder if rental stores rent something like this?
 
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Old 05-17-19, 04:52 PM
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What is it you're trying to do ?
Just locate the conduits or tap into them ?

The tone tracing method is very hard to use as all the conduits will be effectively tied together and grounded....... unless you can specifically disconnect one you are trying to trace at both ends.
 
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Old 05-17-19, 05:07 PM
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Idea is to tap into. I woudl cut an opening near the the conduit and place a GFCI
 
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Old 05-17-19, 05:09 PM
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Keep in mind..... you can't just cut into conduit. You need to pull the wires out first.
 
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Old 05-18-19, 06:02 AM
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The wires will not be long enough to tap into. You are better off coming off an existing box.
 
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Old 05-18-19, 09:04 AM
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It will also be difficult to shoehorn a new box in between two ends of the conduit.
 
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Old 05-18-19, 09:36 AM
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You mentioned wanting to place an opening near the conduit and placing a GFCI, and also that the conduit is on the ceiling. A GFCI receptacle must be placed in an "accessable" location so that it can be easily tested and reset. I doubt a ceiling location qualifies for that.
 
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Old 05-18-19, 11:02 AM
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A ceiling mounted GFI does not meet the requirement of Readily Accessible.
 
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