With all six conductors of a hall stairway three way switch exposed I used a digital meter to test voltages on each. Since it was old wiring (black cloth) and the fact they’re both toggle light switches I had no neutral (line, 2 travellers twice and load). I used the metal box and conduit as a grounded conductor to meter my voltage. I guess I shouldn’t make assumptions. Anyway, if this conduit isn’t grounded and I’m using it as though it were how does that affect my voltage reading? I got 47. Should I double that to find the actual voltage or does this house have a low voltage issue?
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A digital voltmeter is very hi impedence and will detect "stray voltage" caused by capacitive coupling on open circuits.
That 47 volts means that you measured an open circuit.
It might be that the wire that you tested is open, or that the box that you used as "ground" is open.
That is why a lot of electrican use a Wiggly or solenoid test as their primary tester. It is does give much resolution, but it clearly indicates if you have voltage or not.
Since you are unsure of what you have go to an receptacle on another circuit. Measure between the neutral, the wide blade and hot. You could get about 120. And between the neutral and the metal box. If it is grounded then you will read less than 2 volts. It should be zero, but there might be small voltage drop in the neutral. If is abut 120 then the neutral and hot are reversed. If it read something in between then the box is ungrounded.
Then plug in an extension cord and take the other end to you switch.
Use the neutral on that extension cord as your reference. Again a ground or neutral will be near zero. And power will be 120. Open circuits can be something else.
"With all six conductors of a hall stairway three way switchWith all six conductors of a hall stairway three way switch"
Are yous sure of the count. Should be either 5 (power-hot/neutral and 3 wires to 2nd switch) or 7 (the same plus hot/neutral to the light) or even 8.
first let me thank you for such a wonderful response. This is my first posting and you are my first response. You've made this experience very encouraging.
I did not miscount. Or, at least I didn't knowingly miscount.
There are three black cloth (with what looks like some sort of black plastic insulation under the cloth) conductors coming out from each box. To make things harder one lead is barely 3" long. I'm also pretty sure they're 12awg. Does my count not make electrical sense? -- one line in, two travelers and one load out? However, your point about the fixture needing a neutral is quite solid... don't know where it is. The light works. This is all because the client wanted a motion detector installed at the bottom of the stairs. Simple enough I thought.. I'll just replace one of the three ways. Well, five hours later and at least seven calls to Levington's 800# the representative told me to not use their device and call a liscensed electrician.
Back to your points. When you say the conductor is 'open' I'm assuming you mean interupted or not 'hot'. According to my understanding with both three way switches on the floor disconnected and these six wires sticking out of the box and the breaker in the 'on' (energized) position only one should be 'hot', with voltage, or live. the other five are downstream from the one line conductor and thus dead, without voltage, or cold. So, quite simply is the one conductor really only 47volts? I'm kind of amazed I didn't think to bring over another neautral through an extension chord. I will have to try that next. This makes me think 'how can a supply a temporary grounded conductor in other situations?' Could I just pound a metal rod into the dirt and bond a piece of copper conductor on the top? Probably not. But the extension chord idea is a perfect solution in this case.
I did test the upstairs bathroom, kitchen, hallway, computer room and the adjacent apartments' kitchen gfci, hall, bedroom and living room receptacles. All where either 119 or 120. I have also notice old and modern Romex around but have also noticed that the original wiring seems to be this old cloth covered stuff. Needless to say there has been a fair amount of 'from the hip' rewiring. Lots of metal boxes that weren't attached to the bare grounding wire and other things that make you kind of shutter. There's an alarm system, some outdoor lights on a timer and other extension chord led loads all coming into the shared junction box with this three way lighting circuit. It's all metal with some flex metal conduit but looks modern enough to be grounded (code wise at least).
So the question remains...without a neutral if a touch the hot and an ungrounded metal box/conduit what happens to my voltage reading?
I didn't quite understand your first sentence...about the digital meters being of high impedance and thus able to sense wandering capacitive voltages. I did try a simple home depot voltage senso but those things give me too many false posititives for it to be worth it. I've got a nice Fluke digital meter with a red (hot) lead and a black (grounded) lead that will tell voltage, amperes and I think ohms. Maybe I should just check the resistence of the box. Which makes me think that maybe a condoctos sheathing is so bad somewhere in the conduit that an electrical bond has occured between insulated conductor and conduit. Who knows.
Anyway, I really appreciate your feedback and would really appreciate more. If I seems a little rigid it's only to articulate as well as possible this situation.
By the way if you're the same one who brought up the fasteners info 'thank you'. Stainless steel looks better, turns out to fit almost all applications (except if weight is a concern) and comes out to be the best choice. I just buy stainless for all applications and eat the cost. That way I've always got the right fastener for the job.
Cheers,
KSM
"I didn't quite understand your first sentence...about the digital meters being of high impedance and thus able to sense wandering capacitive voltages."I am always bad at analogies and I have not had my coffe yet this morning, but let me try this.The boss tells you that you need some blocking cut to ecactly 10 1/8" You cut a piece and then check with your tape measure makred in 1/16" increments and it is exactly right.But if instead you had a lab instruement that read out in 1/10,000 ths of an and you use it. You picked it up and measure on place and it was 10.1199 and then another place on the 2x4 and it ws 10.1208 and another 10.1305.Well is it "exactly" the 10 1/8" the boss asked for?There are electrical fields from all of the wiring in and around the house (including the power company and also from radio/tv). The meter is sensitive enough that it reacts to those."I did try a simple home depot voltage senso but those things give me too many false posititives for it to be worth it."Those are Great, but limited in what they can do. There main usage is to determine that a circuit is dead. Most realable when you can use it verify both hot and dead. For example you want to work on a circuit and you need to veriy what is on it. You can quickly run it by switches and receptacles and see if they are hot. Then trip the breaker and repeat to see that they are dead."There are three black cloth (with what looks like some sort of black plastic insulation under the cloth) conductors coming out from each box. To make things harder one lead is barely 3" long. I'm also pretty sure they're 12awg. Does my count not make electrical sense?"There have been several evolutions of "romex" Earlier ones just had a cloth type material. Then it was more like a cloth material with a varnish coating. Then a silver coating.The ones that I am familar with tht where used int he 50's and 60's had a rubber type of insulation or an early plastic on the individual wires. About twice as think as current insulation.Here is a list of different ways that 3-ways can be wired. http://www.selfhelpandmore.com/switchoutlet/3way/index.htmThe only way that I can think of that you would have 6 wires is a variation of this.http://www.selfhelpandmore.com/switchoutlet/3way/3waysame.htmWhere a 3rd wire was used from the switch to the light to carry Always Hot so that the circuit could be extended from the light. Possible, but very unusal for a 3-way."Back to your points. When you say the conductor is 'open' I'm assuming you mean interupted or not 'hot'. "I might not have made myself clear and used "short hand".When someone says that they checked the hot at the receptacle and it was 120 volts that is a meaningless statement. However everyone realizes that it is shorthand for meaning that they mesasured between the hot and the neutral.All voltage measurements are measured between 2 points. You have to have a complete circuit, Power source connected to 2 wires (hot and neutral in this case) and then at the other end the meter connected to those same two leads.With a digital voltmeter the only time that you will get a meaningfull reading is when the circuit is completed. Either via the hot and neutral back to the power source (120) or two parts of the "same 'wire'" such as from neutral to ground (where they are connected at the main disconnect) (0v).When I said that it was open it could be from any cause in either wire. That means that there is not a complete circuit through those two wires back to either a common point or power source. That means that either wire might not be connected to anything, wire broken, or siwtch open."Could I just pound a metal rod into the dirt and bond a piece of copper conductor on the top? Probably not."No, the ground is really a poor conductor. "I have also notice old and modern Romex around but have also noticed that the original wiring seems to be this old cloth covered stuff. Needless to say there has been a fair amount of 'from the hip' rewiring. Lots of metal boxes that weren't attached to the bare grounding wire and other things that make you kind of shutter. There's an alarm system, some outdoor lights on a timer and other extension chord led loads all coming into the shared junction box with this three way lighting circuit. It's all metal with some flex metal conduit but looks modern enough to be grounded (code wise at least)."Before wiring with grounds where common (around late 60's early 70's) and before plastic boxes wherever Romex was used you will have ungrounded metal boxes. That was standard for the era. They where only grounded where conduit or BX was used and only when installed properly.In an old house with mixed wiring ASSUME NOTHING. You might have boxes hidden in the walls, "grounds" that are connected to anything, switched neutral, neutral picked up from otherr circuits, lamp cord in the wall, etc, etc, etc. ASSUME NOTHING!A friend of mine bought a house htat had 3-way switch where they ran 2 wire romex and a 3rd separate wire. That separate wire was "joined" in the middle of the run (just on a stud). It looks like a wire nut had been used and twisted so hard that the end brough off. There was 1/2 of one wire with insulation on it "hooked" to and 1/4" bare wire. Sometime it would make contact, sometimes not.And that was not not the worse of the problems.BTW, you might want to look at these for motion switches.http://tinyurl.com/agudjNot true 3-ways, but you can use one at the top and bottom. The lights will turn on with the first detection and stay on until both time out.And here is the company. You can get specs and find local distributors.http://www.sensorswitch.com/
Ksm,
I am somewhat confused when I read your description.
You say 6 conductors, but I think you meant 6 wire ends on 4 conductors (wires.)
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When you measured voltage in the switch boxes, you were either checking from line (hot) to a traveler, or from a traveler to the load (ground), so, you had either a heavenly ground or a heavenly line and who knows what heaven is up to voltage wise. Apparently 47 volts in that house.
Technically, the two open wires (travelers) act as antennae, radiating or receiving just enough power to give a false reading on your hi impedance meter. The term "high impedance" refers to the internal resistance between the two meter leads. A meter with "low impedance" (AKA, cheap analog) has a low enough resistance that the 'antenna' is held to the same voltage as the other wire. Think of the impedance as a resistor in parallel with the meter.
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You will have to run some new wires to make a motion detector work since the M-D must have a neutral return conductor.
EDIT: Have you thought of putting the M-D at the lamp? That would give you a neutral and a switched hot, allowing your client to turn the system off from either switch.
SamT
Edited 6/3/2005 9:27 am ET by SamT
Some of the SensorSwitch (and I think I ran across another version) don't require a neutral and can be used in switch leg applications.
Thank you both very much. You are making this a lot clearer.
I did think that there was a simple solution but it's looking more and more like a strange exception.
ONe last thing. If the metal box and chase were grounded wouldn't the act of measuring voltage between an end of one of the conductors (as a hot) and the 'grounded box' (a neutral) be essentially the same as measuring between the black and green conductors in a properly wired circuit? and so, if the box is not grounded but physically conducts (because it's metal) does that cut my voltage approximately in half (thus 47volts) implying a relatively normal voltage had I supplied a correct neutral (closed circuit)?
SamT... you're right. There are two conductors (line, load) and two travelers. I was just counting the ends of the conductos showing from the boxes.
You guys are awesome. Thank you for you input and website referals.
"ONe last thing. If the metal box and chase were grounded wouldn't the act of measuring voltage between an end of one of the conductors (as a hot) and the 'grounded box' (a neutral) be essentially the same as measuring between the black and green conductors in a properly wired circuit?"Yes, Sorta!Just by being a "black" does not make it a hot. The switch cna be open, etc."and so, if the box is not grounded but physically conducts (because it's metal) does that cut my voltage approximately in half (thus 47volts) implying a relatively normal voltage had I supplied a correct neutral (closed circuit)?"No. while the metal box might be a CONDUCTOR is won't CONDUCT unless it is part of circuit.Just as a short stud is just a short stud untill it is nailed to a king stud and used to support a header, then it becomes a jack stud.A metal box is just a metal box unless is it connected by conductors back to the main disconnect. Then and only then it becomes a ground. Other wise it is "just a metal box".
Mr. Hartmann,
You did it. You answered exactly what I was asking so thank you very much again. This has been a very worthwhile experience. I look forward to future chats, questions and answers with 'Fine Homebuilding's' audience.
Thanks again...KSM
Let us know if you solved the puzzle.
KSM,
You really need to get down to the big bax and purchase Tauntons book on wiring. Your language sux.
Speaking strictly in your home now. All conductors are not wires. All wires are conductors. Salt water is a conductor. Your body is too (albeit, a poor one, as it is also a resistor.) All metal is a conductor. Circuit breakers are conductors. Resistors are conductors. Insulators conduct poorly. Pure H2O is an insulator. Vinyl is. Wood is. Your body is.
Confused yet? Ohms Law; E/R=I. 1/R=conductance. All conductors, resistors, and insulators fall under the 'R.' A MegOhmMeter can measure the conductance of an insulator. A MicroOhmMeter can measure the resistance of a conductor.
It is best to think of all conductors as being extensions of your meter leads because what you are truely measuring is the voltage at the reactive thingamajingy (transformer) or across the load at the end of the conductors (not necessarily wires.) If there is not a continuous conductor (wires, meter leads, conduit, metal boxes, water pipes, etc.) it is said to be an open circuit.
With your meter (Hi-I), in a normal house (anything from the mix and match you're now in, to state of the art) there are only 4 voltage readings you will see; 120 (±10%), 240 (±10%), 0, and anything else (usually about 1/4 full range, whatever range the meter is set to.) If you read "anything else," you have an open circuit between your meter leads and the power companys transformer.
Which gives us an easy way to tell. If you read 47 VAC on one meter range, change the meter to the next higher range. If the reading changes (to about 1/4 of the new range,) you're measuring heavens voltage. (|:>) If it still reads 47 volts, then you've got an issue.
A few words on nomenclature, 'cuz when you fully understand the terms, you will understand household wiring
Supply wire, AKA hot; A wire connected to a breaker or fuse, thence thru the meter to the PCs' transformer.
Return neutral conductor, AKA neutral; A wire connected the the neutral buss or the ground/neutral buss in the breaker box, then to the ground rod, thence thru the earth to the PC.
Equipment grounding conductor, AKA ground; A conductor/s providing an unbroken path to earth, usually thru the ground buss or the neutral/ground buss to the grounding rod.
Notes;
The hot and neutral are wires. Ground doesn't have to be.
Hot and neutral are the power supply.
The hot and neutral both conduct back to the power company (PC)
Neutral and ground both connect to the earth.
Neutral and ground are both at zero volts potential with the earth.
Ground is for safety, not power.
Problems;
Hot; any conductor (wire, pipe, refrigerator, human) with a continuous path back to the PC transformer.
Grounded, AKA sparking, AKA popped breaker; any hot with a continuous path to ground.
Open; any conductor, one end ofwhich, does not connect to ground, the PC transformer, or the load, whichever is appropriate.
SamT