Is 97 volt AC a possiblity in a wire to nowhere?

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Tbbarch

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First - my appreciation for house wiring stops at correct new installations.
I do not know what happens over time or when things get creative.

I am replacing a line voltage thermostat that operates a fan in a fan coil. The cabling is #14 metal jacket to ground (BX). The cable may be running through metal plaster truss "studs".

See pic.
Checking the wires I find I have 97 volts from the hot wire to the wire that runs to power the fan.
But the fan is disconnected and wire is capped. No load?

At present I am guessing the wire to the fan is running as a third wire in 3 cable #14 to get it through several outlet boxes to the fan coil. There is one outlet I have yet to get access to to "know" my guess is correct.

I have been hearing that this is inducted voltage. 97 induced volts seems high for the few things that are plugged into outlets on the circuit.

So, is 97 induced volts possible over a distance of 26 feet when the hot wires being shared are carrying little load?

Is there a load in a hot wire even if the circuit is not closed?

Where can the 97 volts be going?

Do I have a problem and are there any suggestions on testing to determine where it is?

05.3.Fan coil wiring notes.jpg
 

Jadnashua

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When measuring voltages, one critical thing is what is your reference. A switched leg has no reference between its two wires. If you were to measure between one lead and a solid ground, I think that you'd find different results. In one case, I think you're measuring hot to ground, and in the other, you're measuring hot, through the motor windings to ground. Without seeing the whole picture, that is just a guess.

Do those two wires go into the thermostat? Usually, all a thermostat does is connect the two leads together once it calls for heat. It is acting like a switch.
 

DonL

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Do I have a problem and are there any suggestions on testing to determine where it is?

From your drawing and readings, It looks like your Neutral and Hot are swapped.

The best way to test to see if you are reading a Ghost voltage, Is to use a small light bulb or Neon bulb tester.

upload_2016-11-17_4-51-54.jpeg

Good Luck.
 

Tbbarch

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When measuring voltages, one critical thing is what is your reference. A switched leg has no reference between its two wires. If you were to measure between one lead and a solid ground, I think that you'd find different results. In one case, I think you're measuring hot to ground, and in the other, you're measuring hot, through the motor windings to ground. Without seeing the whole picture, that is just a guess.

Do those two wires go into the thermostat? Usually, all a thermostat does is connect the two leads together once it calls for heat. It is acting like a switch.


Did you see the picture?
Yes the wires go to the thermostat and it is just a switch connecting the wires. The wires are not connected to the thermostat.
There is not a motor on the other end. The wires are unconnected.
The box is ground.

You may be right about needing better reference points.
I am just not clear on what they are.
I am going to wire across the room and do my tests as if these were powering an outlet.

I did read something ( http://m.ecmweb.com/content/diagnosing-power-problems-receptacle ) that indicated my numbers would be indicative of the circuit when it is loaded. But there is not load to a fan. I can't help feeling I'm missing something.
 
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Tbbarch

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From your drawing and readings, It looks like your Neutral and Hot are swapped.

The best way to test to see if you are reading a Ghost voltage, Is to use a small light bulb or Neon bulb tester.

View attachment 36967
Good Luck.

With a test light:
White wire to Black wire = POWER
White wire to ‘J’ box (ground) = POWER
Black wire to ‘J’ box (groud) = ZERO
 

Reach4

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A neon tester is high impedance too, so it can glow from just capacitive coupling. You may even get it to glow dimly by connecting one lead to a wire and holding the other lead with your fingers. Don't touch any other conductors with your body if you try this one. You can try the same with your voltmeter. Hold one prob

Consider using the prongs of a 120 volt lamp cord or a string of Christmas tree lights as a test indicator. If you get that to glow, you have a serious mis-wiring somewhere.

I would even consider touching the white wire to the box. If you got a spark or popped a breaker, it would have been a worthwhile test showing a serious problem. If, as expected, no spark and no breaker pop, you just have capacitive coupling.
 

DonL

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With a test light:
White wire to Black wire = POWER
White wire to ‘J’ box (ground) = POWER
Black wire to ‘J’ box (groud) = ZERO

Neutral should be white not black. Black should be a hot leg.

They are swapped/backwards. White and ground should be near the same potential.
 

Reach4

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White and ground should be near the same potential.
If I read tbbarch correctly, the white wire is not connected to anything at either end. Did I read wrong?
 

DonL

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If I read tbbarch correctly, the white wire is not connected to anything at either end. Did I read wrong?

It must be connected to something. L1 or L2 somehow.

With a test light:
White wire to Black wire = POWER
White wire to ‘J’ box (ground) = POWER

Black wire to ‘J’ box (groud) = ZERO

Sounds like some used black as ground, That is true for DC but not AC.
 
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Reach4

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It must be connected to something.

With a test light:
White wire to Black wire = POWER
White wire to ‘J’ box (ground) = POWER
Black wire to ‘J’ box (groud) = ZERO
I suspect this is from a neon tester. Neon testers can glow (but not full brightness usually) by very small capacitively coupled currents. The power can be very tiny.

If this was known to be a tester with an input impedance under 100 kohm, then I would share your concern.
 

DonL

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I suspect this is from a neon tester. Neon testers can glow (but not full brightness usually) by very small capacitively coupled currents. The power can be very tiny.

When a neon bulb fires it draws current.

These work, They have neon bulbs.

upload_2016-11-17_14-7-57.jpeg
 

Jadnashua

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Is the fan 120 or 240vac? If 240vac, they may only be switching one leg, not both...still works since it opens the circuit.

Are both leads at both ends disconnected?

Does the lead control more than one unit?

Long time ago, was testing the filaments of a power tube...5vdc from one end to the other, but from one end to ground - 4000v, and on the other side 4005v...reference is critical!
 

WorthFlorida

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  1. The first place to start is turn off circuit breakers one at a time until these voltage readings disappear and mark the breaker. Turn on all other breakers that were switched off.
  2. Recheck for voltage at the thermostat wiring. Hopefully there is no voltage. If there is start turning off other breakers. As stated before, might be switched 220v.
  3. If no voltage, then go around to outlets and switches that have no power and mark them, if any. Check for any juncture boxes around the heating system.
  4. Turn the breaker back on and recheck the marked locations for voltage. Any without power would be a suspected location to open up first.
  5. Turn off the breaker and start opening up the outlet or switches and check wring.
 

Tbbarch

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Thank you gents.

There seems to be some drift happening.

The WHITE WIRE is the POWER WIRE.
The BLACK WIRE is the power wire to the fan coil when the thermostat turns the switch ON. So the fan is a non-existent 120 v motor.

I do not understand the confusion over the reference points.
-White (power) to Black is 97.3 v and there is NO FAN or anything else connected.
-White (power) to B0x (ground) is 121.7 v
-Black to Box is 19.7 v.

Since last visit to the forum I have isolated the circuit and checked every single outlet box on it.
Though I found some ground wire issues, corrections did not change the readings at the thermostat box.
I also learned the wire to the fan coil from the thermostat gets there by sharing a ground cable jacket with two other wires ... it runs through a Red wire through two other boxes before getting back to Black at the fan coil where the White is the Neutral.

In learning something about diagnosing outlets I decided to run a wire across the room to test the thermostat wiring as if it were just powering an outlet.
- In that case everything reads normal.
-- Power wire to Ground jacket is 122 v
-- Power wire to Neural is 123.4 v
-- Neutral to Ground is 0.089 v
-- Ground to Ground is 0.003 v
-- Black wire at thermostat box has continuity

I am finding my Craftsman low end multi-meter is fluctuates in is readings by a couple volts on powered wires and reads voltage in the air (which I've assumed and heard tell is normal). So the 121.7 to 123.4 I feel is negligible and anything under 1 I also ignore.

I have also wired the fan coil end to a lamp plug and the lamp operates without blowing a circuit and the connections read normal.

So at this point I am left with the explanation that this is induced voltage
BUT
without anything being powered by the other outlets on the breaker to "induce" (?) it.

05.4.Fan coil wiring notes.jpg
 
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DonL

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I do not understand the confusion over the reference points.
-White (power) to Black is 97.3 v and there is NO FAN or anything else connected.
-White (power) to B0x (ground) is 121.7 v
-Black to Box is 19.7 v.

Your outlet wiring is wrong.

This is the way it should be.

upload_2016-12-2_17-45-22.jpeg
 

DonL

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Since the question is not about and outlet, will you explain how this is helpful?

If you do not know the proper way for a outlet to be wired, You should not be playing with electricity.

I just do not like to see people make simple mistakes, and hurt themselves.

Have a great day.
 

Jadnashua

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FWIW, most of the readily available, digital voltmeters out there have a VERY high input impedance. This means that while there may be an induced voltage, it has no current carrying capacity, but shows up because the meter has maybe a megaohm or more per volt input impedance. An old analog meter might be more in the range of 20K-ohms/volt. The difference is, a DMM puts nearly no load on the circuit, whereas an analog meter does. No load can read an induced a voltage, high load, it gets bled off (Ohms law).

If you do not understand the difference, and that a high voltage COULD have a very real danger to it, you either need to educate yourself, or not play! A static discharge could be many 10's of thousands of volts, but has nearly no current associated with it. Course, I did once see a guy get zapped by a 40KV radar power supply...it burned a channel through his arm, out his hand, and also scorched the nails in his heels of his boots...not pretty. He failed to discharge the supply properly and used the override on the safety interlock.
 
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