Possible to detect precise location of wire break?

Reply

  #1  
Old 10-09-19, 12:01 PM
Member
Thread Starter
Join Date: Mar 2009
Location: Northern Virginia
Posts: 3,892
Received 1 Vote on 1 Post
Possible to detect precise location of wire break?

I went to reconnect my garage door opener this past weekend after having drywall installed, and realized there is an open/break in one of the conductors of the 2-wire that runs from the control panel by the house entrance and the opener above the door (jackshaft opener). I'm guessing I either stapled the wire too tight and broke it, or the drywall guys put a screw through it. Regardless, I'm curious if there is a way to locate the precise location of the break without cutting holes in the drywall and accessing the wire? Is there a tool that can detect the location of an open circuit? It may be cheaper to just fish a new wire, but it's a12' vaulted ceiling with no attic access and I don't really want to cut a bunch of holes in my brand new drywall. If I connected an AC voltage signal to the broken conductor, would I be able to detect the location of the open using a capacitively-coupled no-contact meter?
 

Last edited by mossman; 10-09-19 at 12:16 PM.
Sponsored Links
  #2  
Old 10-09-19, 12:04 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 52,689
Received 343 Votes on 321 Posts
I just had a call where I found one of the sensor eye lines was shorted in the wall.
I abandoned it and stapled a new wire in place. It's only a garage.

You could probably use a fox and hound tracer to locate the open but it will be easier to just abandon the line.
 
  #3  
Old 10-09-19, 12:30 PM
Member
Thread Starter
Join Date: Mar 2009
Location: Northern Virginia
Posts: 3,892
Received 1 Vote on 1 Post
I'll probably just cut holes and fish a new wire or just mount the panel by the garage door.
 
  #4  
Old 10-09-19, 12:33 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 52,689
Received 343 Votes on 321 Posts
My customer was adamant that it couldn't be a shorted wire as it had worked for 15 years.... but it was shorted. I couldn't explain it and it would be almost impossible to find without opening the rock.
 
  #5  
Old 10-09-19, 01:03 PM
Member
Join Date: Oct 2005
Location: USA
Posts: 1,331
Received 6 Votes on 6 Posts
  #6  
Old 10-09-19, 03:13 PM
Member
Join Date: Oct 2015
Location: Ct.,USA
Posts: 1,183
Received 28 Votes on 24 Posts
Telecom guy, I doubt many DIYs have an oscilliscope in their toolbox. The TDR by itself does not tell you anything.
 
  #7  
Old 10-09-19, 03:37 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 52,689
Received 343 Votes on 321 Posts
I actually carry a handheld TDR but wouldn't even break it out for a job like this.
 
  #8  
Old 10-09-19, 04:33 PM
Member
Join Date: Oct 2005
Location: USA
Posts: 1,331
Received 6 Votes on 6 Posts
It won’t be long when they will work with a smart phone.
 
  #9  
Old 10-09-19, 04:58 PM
Member
Join Date: Nov 2012
Location: USA
Posts: 1,229
Received 23 Votes on 19 Posts
It won’t be long when they will work with a smart phone.
Most Android phones now come with a FM tuner chip.

I VAGUELY remember my computer-engineer-Dad tracking down a break in an undergound wire to an outside light post by flipping the breaker, jumpering the hot wire to the distributor cap of a running car, then using a transistor radio to track down the signal.
 
  #10  
Old 10-10-19, 06:21 AM
Member
Join Date: Jan 2014
Location: USA near Boston, MA
Posts: 676
Received 19 Votes on 15 Posts
Distributor cap?
Transistor radio?

Yeah, that was a while ago.
 
  #11  
Old 10-10-19, 07:10 AM
Member
Join Date: Nov 2012
Location: USA
Posts: 1,229
Received 23 Votes on 19 Posts
<quote>Distributor cap?
Transistor radio?
Yeah, that was a while ago.
</quote>

At least is was a BREAKER, not a fuse....

The point is, if you can put a FM signal onto a broken wire, a modern android phone should be able to pickup that FM signal.

It should ALSO be possible to do something similar with a WiFI signal, especially since there are so many "WiFi signal strength" apps out there.
 
  #12  
Old 10-10-19, 08:04 AM
Member
Join Date: Jan 2014
Location: USA near Boston, MA
Posts: 676
Received 19 Votes on 15 Posts
Last summer I bought a

Noyafa NF-816-C Underground Cable Wire Locator Locate Pet Fence Wires, Metal Pipes, Electrical Wires, Telephone Wire, Coax Cable with Earphone

on Amazon for $39 and was able to find a buried valve box in my irrigation system. According to the instructions you can also use it to find breaks in electrical wires behind walls.
 
  #13  
Old 10-10-19, 08:28 AM
Member
Thread Starter
Join Date: Mar 2009
Location: Northern Virginia
Posts: 3,892
Received 1 Vote on 1 Post
I actually have a working analog Tektronix 2230 oscilloscope.

Injecting and AC signal on the broken wire and sniffing out the electric field with a no-contact meter isn't viable?
 
  #14  
Old 10-10-19, 09:07 AM
Member
Join Date: Oct 2005
Location: USA
Posts: 1,331
Received 6 Votes on 6 Posts
This is small zip cord, correct? and, only one side has the deficit/break?
I suspect the no-contact sensor will not detect a normal 60Hz signal over an inch away. I have problems with them when trying to detect a line voltage outside a TR receptacle. Maybe my G-B unit is not very sensitive.

Could be a AM transistor radio has merit with noise injected on the one wire. I have heard that using a small voltage source with a wire end running along a file makes a hellatious signal on an AM radio.
 
  #15  
Old 10-10-19, 09:26 AM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 52,689
Received 343 Votes on 321 Posts
You could try using a Fox and Hound type tracer. You'd need to short the wires at one end and inject on the other two wires. I have found open alarm wires this way.
 
  #16  
Old 10-10-19, 01:41 PM
Member
Thread Starter
Join Date: Mar 2009
Location: Northern Virginia
Posts: 3,892
Received 1 Vote on 1 Post
Small gauge solid copper 2-wire with only one conductor having a break in it. The wire is just on the other side of the sheetrock, about 1-1/2".

Would this tool work? A Youtube video showing its operation implies it would: https://www.amazon.com/gp/product/B0...k_ql_qh_dp_hza
 

Last edited by mossman; 10-10-19 at 02:04 PM.
  #17  
Old 10-11-19, 08:19 AM
Member
Thread Starter
Join Date: Mar 2009
Location: Northern Virginia
Posts: 3,892
Received 1 Vote on 1 Post
I spoke with a couple guys at work and they made a good point...the tone would couple into the second wire and make it nearly impossible to detect the break in the other wire. Unless maybe I ground the second conductor?
 

Last edited by mossman; 10-11-19 at 08:46 AM.
  #18  
Old 10-11-19, 08:25 AM
Member
Join Date: Oct 2005
Location: USA
Posts: 1,331
Received 6 Votes on 6 Posts
Yeah, I was thinking the same thing. Also, are the drywall screw heads still exposed? You could consider using needle DMM probes and see if a screw head has continuity to either wire. Is this steel stud or wood stud wall?
 
  #19  
Old 10-11-19, 08:42 AM
Member
Thread Starter
Join Date: Mar 2009
Location: Northern Virginia
Posts: 3,892
Received 1 Vote on 1 Post
Yeah, I was thinking the same thing. Also, are the drywall screw heads still exposed? You could consider using needle DMM probes and see if a screw head has continuity to either wire. Is this steel stud or wood stud wall?
No. It is all finished and painted. Wire runs through the ceiling (trusses with no attic access).

I did a little experiment (found a meter at work) and I may have found a configuration that could work. I laid out a 6' length of 2 conductor wire on the table, connected the red lead to the broken wire, connected the other three ends of the wires together and to the black lead and found that the tone gets nearly silent where the open is. Think I'll take the meter home and try it out.
 

Last edited by mossman; 10-11-19 at 09:03 AM.
  #20  
Old 10-12-19, 05:05 PM
Member
Thread Starter
Join Date: Mar 2009
Location: Northern Virginia
Posts: 3,892
Received 1 Vote on 1 Post
It worked! I was skeptical at first, but identified a spot to where the amplitude of the tone decreased significantly, cut a 6" hole in the sheetrock, and located the section of wire with the severed conductor. Patched the wire and all is good now
 
  #21  
Old 10-15-19, 07:44 AM
Member
Thread Starter
Join Date: Mar 2009
Location: Northern Virginia
Posts: 3,892
Received 1 Vote on 1 Post
For anyone curious as to why it worked, the source signal fed into the wire is an AM signal. When I twisted the opposite ends together the source signal travels back towards the source on the parallel conductor 180 degrees out of phase, which doubles the amplitude of the AM signal and thus doubles the signal picked up by the receiver probe. This is why the tone is so much louder along that section of wire then gets half as loud from where the wire break is up to the source. Not sure I explained that clearly, but for those of you that understand RF, it should make sense.

https://www.mediafire.com/view/lm0ed...racer.jpg/file
 

Last edited by mossman; 10-15-19 at 08:54 AM.
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
Display Modes
 
Ask a Question
Question Title:
Description:
Your question will be posted in: