Non-Contact Circuit Continuity Tester

After checking resistance after laying about 20 tiles I found an infinity reading indicating a broken wire.

Why didn't you try to find out where it was at that time?

Mike,thanks for the reply. I did try to find some physical indication of where the open was but since the tiles are over the wire the only indication that I had was when I tested, by then the adhesive had set. Since then I have found out there is an audible monitor that you can put on the wires that will sound immediately when continuity is lost. The question remains, how do I find the fault now?

Yes I can do that. Never thought of feeding in 120V. I'll try that. It doesn't matter if I am an inch or two away, the fault should be be either under one tile or two adjoining tiles. The company that manufactures the cable sends a rep , at a cost, and he pumps in enough voltage to cause an arc. Then they scan with infra red scope to see the hot spot on the tile. I'll try myself first to see if I can locate it. Thanks. GA

GA and a good tool. I have used it for years with great results. And affordable too.

Regards.

This type of Testers are used to detect the Short-Circuits in a open-cables while walking & not in open-faults. May be of little use in burried cables.

Moreover a separate tone generator is required to use.

Haajee

Regards.

A GA for good info links.

But I think that TDR is not is normally for Transmission Cables & a costly solution.

Of course TDR can be used for such problem faults.

GA. You said to connect 120V to only one wire. You should specify that it must be the hot side of the 120 V (black wire, shorter flat hole in the US), and that it will only find the break if the break is in that wire. if the break is not found on the first trace along the cable, then the hot side of the 120V would have to be connected to the other wire and repeat the trace. Power line frequency has the advantage of practically no inductive/capacitive coupling to the other parallel wire. The audio and especially RF frequencies will have such coupling, which may make it harder to find the break.

Fluke has the "VoltAlert" which is similar to the Greenlee unit, for under $30. Mine is an early one, and has to be within about an inch to 'see' 120V. There is a newer model that works at lower voltage, so should see 120V from a little farther away.

I use mine every Christmas to find the failed lamps in series Christmas light strings.

Among other places, the Flukes are sold at Sears and Graingers. I'm pretty sure I've seen a cheaper version from China at Home Depot.

WOW, where have I been Hiding? I just returned from my local Home Depot. My Fluke is probably 10 years old, and only works down to 90V, if I recall correctly. The Greenlee supposedly works down to 5V, and is only $16, so I bought one. I'm anxious to try it! If there had been one made in USA, I'd have gladly paid twice as much, but no such luck!

DOUBLE WOW! In one case the Greenlee was able to indicate the presence of 120V 60Hz from about a foot and a half away through air, and could easily trace the path of a 3-wire 120V cable behind drywall, from several inches away from the wall. It could not trace the same cable from the outside, which is no surprise, as there is a layer of aluminum foil on the insulation. I'm really impressed!

Welcome to the insanity. Nice answer.

You can use a short wave or "CB" radio, noticeable interference will correspond with the break just wave the antenna over the tile.

How about one of these non-contact voltage testers? The one I have will find a break in a mains cable just by running the tester along the cable. It will also find live cables in cavity walls. The one I have linked to is a really cheap version, there are better ones from Fluke.

This technique works with shielded cable but I'm not so sure with twisted wire. Basically you measure the capacitance at both ends and the ratio between C1 and C2 will give you the same ratio in distance units. No harm in trying.

regards,

Vulcan

My heating wire is actually not as you have drawn. There are only two ends. The circuit is simply one wire in a loop. It is resistive wire and the two loose ends are connected to 240v. It would not help to know the distance to the break because the wire is weaved back and forth across a 20'X 10' room about 4"-6" apart. I can only get to within about 1/2" of the wire with a tester where it is under the floor.

Back in the 60's or thereabouts, there was a heating system called Ceilheat which worked just this way. There were numerous failures which lead to the system falling out of favor and home buyers demanding a more reliable system but you may be able to google Ceilheat and find a contractor/installer that can find your location reliably. (By the way, I am betting on your connection point to the contactor or controller, or an open at your short at the far end, a broken wire after it is installed is a mite rare...)

I had a fairly cheap little led flashlight from fluke that had a voltage tester on it until it got broken. It would indicate which side of the outlet was hot by an LED that glowed red when you passed it by the slot. It would glow blue (i think) for ground side. You only had to be in the proximity of voltage for it to glow. If you had something like this you could follow the wire from above the tile until the LED stopped glowing red and started glowing blue only. Here's a link to one: http://www.toolup.com/fluke/lvd2.html

Well, I bought a tester and tried it on a few things around the house. It really worked well. Then I tried it on the floor heating. It worked a bit but you could not rely on the result, too sketchy. Then I realized probably why it doesn't work on the heating wire. The problem is that the heating wire inside the sheath is arranged as a twisted pair of conductors unlike the side by side in a normal piece of house wiring conductor. Any EMF present is minimized by the arrangement and the sensor of the probe doesn't see a lot of EMF. It worked well down to the connection to the twisted resistive cable but after that not well at all. I'm out of ideas. Anybody else?

How did you connect mains to the loose wires?

1.) Live to one and neutral to the other. OR
2.) Live to both shorted together.

If you get different results there may still be a way. Can you get hold of some resistors, and a mains transformer (a shaver socket will do)?

Live to one, neutral to the other. Then also live to one only at a time and no difference in readings.

I'll have to try live to both shorted together today. That should eliminate some of the twisted pair shielding.

Live to both shorted together will virtually guarantee failure (unless both wires are broken), because the good wire will carry the signal past the break in the bad wire.

I just did a bit of experimenting, and with the Greenlee, I was able to adjust the sensitivity until I could trace a twisted pair (actually three twisted conductors - a standard computer power cable; hot, neutral, and ground, plugged in, but no load) behind a 3/8" ceramic tile and a 3/8 layer of wood. The minimum sensitivity that detects the signal will pulse on (when the hot wire is closest) and off as you run along the cable. There should be a pretty regular separation distance between on pulses. Increasing the sensitivity should increase the on portion and decrease the off portion.

Ya' mean your heater (resistive) wire is twisted??? I have seen non-resistive, twisted wire connected to a long, single, resistive wire that's serpintine-laid under tile and returned to neutral, but I've never seen twisted resistive wire.

There is a piece of test equipment available, it is called a TDR. Time Domain Reflectometer. This piece of kit will tell you exactly where the break is in the cable to the millimeter.

These are not cheep, try to borrow one or possibly hire it.

Regards

Steve

Guest, I read up on the TDR. Unfortunately you would have to know where the cable is located under the floor. The TDR gives you the distance to the fault but if I don't know exactly where the cables are under the floor the fault distance from the test site doesn't tell me where in the floor it is. Thanks for the info.

I've laid under floor heating in two houses. And there is an obvious requirement to know where the wires (pipes in my case) are, as you must space them +/- equidistantly to get an even heat distribution.

Given that it seems to me that Vulcan's idea should get you close. You do say you can get to the splice, and therefore we suppose, split it.

Regards

Chas

Yes I probably could split the splice.