Wiring question

Andy comments:

You forget that the neutral circuit is connected to ground in the panel. Nobody can get "shocked" by touching two separate white wires, assuming they are connected together in the panel, where they are also connected to the bare copper safety wiring, which is also connected to the big metal rod which goes into the ground, as well as the center conductor of the transformer on the pole (or wherever), which also goes to a ground rod......etc....

Draw yourself a schematic , and you will understand.....

Andy in Eureka, Texas

Reply to
Andy
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Andy comments

Well stated....

Andy in Eureka, Texas

Reply to
Andy

Andy comments: Absolutely right .... That's why it isn't a good idea, since some hypothetical future problem would open up the neutral path back to the panel.... Incidentally, this problem also happens when the screw to the little white wire in the panel gets loose, or corroded.... which is why I reccommend tightening up the screws in the neutral bar in the panel every few years or so.... This can also cause an "apparent" voltage drop to the appliances being used, and is normally one of the first things to check when that happens....

Andy in Eureka, Texas

Reply to
Andy

Certainly not a realistic situation. 14AWG copper has a resistance of approximately 3 milliohms per foot, so your hypothetical 50 milliohm resistance represents just seventeen feet of 14AWG copper. I submit that most points in most residential circuits are a *lot* farther than 17 feet from the panel.

Do you have references for any of these numbers, or did you just make them all up like the 500 ohms you "picked out of thin air" a couple paragraphs back?

The resistance figures given here

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FAR lower than yours. I think I can be pardoned for believing documented numbers from NIOSH and the IEC just a bit more than I believe your numbers "picked out of thin air".

It's not.

It also assumes your resistance figures are correct -- which I very, very much doubt.

Do your calculations again, with realistic resistance figures this time (both for the human body, and for the neutral wire), and see where it leads you.

500 milliohms is the resistance of approximately 170 feet of 14AWG copper; there is at least one 15A circuit in my house where the last outlet is very nearly that far from the panel. What makes you think that indicates a "VERY BAD" ground?
Reply to
Doug Miller

32 feet of 14 ga copper has 82.8 milli-ohms of resistance. At 15 amps, that is a total voltage drop of 1.23 volts at 15 amps. That is OVER AND ABOVE the resistance of the "connection" I was refering to.

So lets say the wire is 32 feet long - from the point where you are working on the circuit - and we have my theoretical .05 ohm connection resistance for a 2 volt drop. That's a 30 watt total dissipation. and a current flow through the 500 ohm body of less than 4 milliamps.

My 500 ohms "picked out of thin air"s actually pretty darn close, according to my sources noted below.

I had gotten the same numbers from several sites that I looked at - which appear, according to your Wikipedia reference to be out by a factor of 10 but I don't take Wiki information as gospel. My primary source was

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Also look at
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uses 500 ohms resistance as "worst case" resistance.

Page 220 of

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500-1000 ohms as the minimum resistance of the body EXCLUDING SKIN RESISTANCE. The resistance of "intact dry skin" according to the same sourse is "quite high". These resistances are between any two limbs. Resistance across the chest - say laying on the ground with a defective tool on a bare sweaty chest could be as low as 100 ohms.

Another reliable source, in my eyes, is

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indicates 2330 ohms hand to hand and 1130 hand to foot according to measurements done by Charles Dalziel in the 1940s and 50s.

Regardless, we are talking running that circuit at FULL LOAD - so even with YOUR numbers, it is far from "dangerous"

Reply to
clare

Licensed Electrical

exas- Hide quoted text -

Obviously the whole discussion is way beyond your comprehension at this point. An analysis has been given based on parallel circuits with some real resistances that show you can in fact get shocked. And that is because those neturals are not perfect conductors, they do have resistance, and hence there can be voltage potential between them at various points along their runs and ground.

Will it kill you, shock you severly, or burn down your house? Probably not, IF everything you assume and everything in the other circuit you tap into is working correctly. And IF someone in the future doesn't come along and add on to the wall switch wiring, putting in more outlets for example, then you have do have something with lethal potential. How lucky do you feel gambling with other people's safety?

The other interesting thing is that you and CL presume to know exactly the amount of current that unknown, generic X10 switch will send down this illegal tapped neutral. We don't even know which specific one it is or what the actual current it will send down the neutral is. CL is making the assumption that it is almost non-existent. Since we don't even know the specific switch obviously neither of you can know that.

Suppose it's instead 30ma which is enough to kill someone working on the other circuit which they believe to be de-energized? These X10 things are cheap crap made in China, so how do you know it won't have some failure that results in say 75ma going down the neutral which is enough to kill someone? How about someone replaces that X10 with something else someday, say a combined switch and outlet that sends 5 amps down the neutral?

Those are the real safety issues the folks who write the NEC are aware of and why the rule exists.

BTW, Doug and I are still waiting for an answer from you guys who think tapping another neutral is an OK idea. If you can run a new neutral back to that X10 switch, from another circuit, then why can't you just run a hot back there too, connecting the X10 switch to the hot and neutral from the same circuit? Last time I checked, Romex has two current carrying conductors, so the wire is free. You could almost always do it safely and legally with the same amount of work, same cost, so why are you advocating doing this half-assed nonsense?

Even more bizarre, if his loads are just incandescent lights, the whole problem can be solved by just using an X10 swtich that works without a neutral at all. They are readily available.

Reply to
trader4

That is, quite simply, utterly false. If you are grounded, and touch the neutral wire of an energized circuit, you *can* get a shock because you've created a parallel circuit, one leg of which is your body.

Take your own advice.

Reply to
Doug Miller

Andy comments:

CL, I am reminded of a quotation from Mark Twain :

"Never try to teach a pig to sing....... It wastes your time, and annoys the pig "

---- Mark Twain

I'm sure that both of us have better things to do .......

Reply to
Andy

That's pretty much the same conclusion I'd reached in regard to attempting to explain the concept of parallel circuits to you.

Reply to
Doug Miller

Doug, without proof, I'm not buying into that it's a tiny current. We don't even know the specific X10 switch he's contemplating using. We do know that it's one that works any load, not just incandescents. All the ones of that type I have seen have relays. You can hear them click. A relay needs some reasonable current to pull in and I would think that current is flowing in the neutral, meaning it could be 30ma, the lethal threshold.

I think it's totally irresponsible to be advocating using a neutral from another circuit with a device that no one here even has a spec sheet on. CL and Andy are assuming the X10 switch has a "tiny" current, but no one knows that.

Another easy to understand major safety hazard is someone later replacing that X10 switch with a switch/outlet combo. Now, you have the ability to:

A - exceed the current carrying capacity of the neutral resulting in a fire

B - having the other circuit neutral with 120V when someone working on it believes it's de-energized because they opened the breaker.

Reply to
trader4

Andy comments:

You are correct. X10 modules use internal relays....typically they are "appliance modules" which have a specific current rating, and are "reccommended" for passive, not inductive, loads (for obvious reasons).....

I use them all over the place in my house , and have written programs and built interfaces to run them from laptops, and , when I needed to have one do "more" than their ratings, used a big ass contactor (technical term for... well... big ass contactor ) to handle the problem....

Andy in Eureka, P.E.

Reply to
Andy

What does the above have to do with anything? Can you state what current the X10 switch Ivan is actualy planning on using sends down the neutral? CL and you assume it's near zero and so it just can be dismissed as harmless. I say without a spec sheet and knowing an energized relay is involved, you're full of BS.

Reply to
trader4

The no neutral incandescent only switch would most likely be a WS467, and the flourescent control (with neutral) would likely be an XPS3 (relay) switch. If the relay is operating on 110 volts nominal voltage, it will, in all likelihood, draw aprocemately 1ma - as MOST miniature relays have

85 to 110 mw coils. Lets go worst case at 110mw on 120 volts - that is 0.91 ma. The AVERAGE person will not even detect current flow of under 1 ma. My OLD GE plug-in remote control appears to draw just over 10ma of current at 117 volts, but it has a transformer in it where the X10 wall switch most likely uses a miniature switcher to provide the low voltage. Anyone have an XPS3 and a multi-tester to settle this once and for all???? And again - I would NOT advocate running an "orphan" neutral into the box.
Reply to
clare

Can you measure the activation current on one of your "appliance modules" and put this turkey to bed???

Reply to
clare

Andy cmments: It was easier to just google it. Here is a statement made on X10 modules used with LEDs :

******************************Cut and paste ********** In the OFF state, most X10 appliance modules draw between .1 and .5 watts, depending upon the make and model. ************* end of cut and paste. *******************

So 0.1 / 110 is .000833 or about 8/10s of a milliampere.....

I'll have to go and measure the relay current in the "ON" state....

Andy in Eureka, P.E.

Reply to
Andy

32 feet of 14 ga copper has 82.8 milli-ohms of resistance. At 15 amps, that is a total voltage drop of 1.23 volts at 15 amps. That is OVER AND ABOVE the resistance of the "connection" I was refering to.

So lets say the wire is 32 feet long - from the point where you are working on the circuit - and we have my theoretical .05 ohm connection resistance for a 2 volt drop. That's a 30 watt total dissipation. and a current flow through the 500 ohm body of less than 4 milliamps.

My 500 ohms "picked out of thin air"s actually pretty darn close, according to my sources noted below.

I had gotten the same numbers from several sites that I looked at - which appear, according to your Wikipedia reference to be out by a factor of 10 but I don't take Wiki information as gospel. My primary source was

formatting link
Also look at
formatting link
formatting link
uses 500 ohms resistance as "worst case" resistance.

Page 220 of

formatting link
500-1000 ohms as the minimum resistance of the body EXCLUDING SKIN RESISTANCE. The resistance of "intact dry skin" according to the same sourse is "quite high". These resistances are between any two limbs. Resistance across the chest - say laying on the ground with a defective tool on a bare sweaty chest could be as low as 100 ohms.

Another reliable source, in my eyes, is

formatting link
indicates 2330 ohms hand to hand and 1130 hand to foot according to measurements done by Charles Dalziel in the 1940s and 50s.

Regardless, we are talking running that circuit at FULL LOAD - so even with YOUR numbers, it is far from "dangerous"

Reply to
clare

I say it's totally irresponsible to be encouraging someone to tap into a neutral on another circuit based on guesses as to the design and operating charecteristics of an X10 switch they would install when you don't even know which one it is or how much current it sends down the neutral.

And I've asked about 5 times now. If he can go find another circuit's neutral and run a wire from that to the switch, then why the hell can't he just run a hot back as well and make it code compliant and safe?

That wouldn't settle it because we don't know which switch actual he has. Or which switch he or someone else will replace it with in 2 years when it fails. How about they replace it with a switch/receptacle combo?

I sure looks like the two of you are giving it the green light by claiming it's safe.

Reply to
trader4

Andy adds: On second thought, nothing is going to "put this turkey to bed", regardless of the information presented. There are different mindsets on this, and it's up to Ivan to figure out what he wants to do . Beyond that, it's really nobody's concern.... Good luck to Ivan.... !!!

Andy in Eureka, Texas

Reply to
Andy

It's not up to Ivan to figure out. That's why we have the NEC which specifies how wiring is done safely.

=A0> =A0Beyond that, it's really nobody's

I'd say it's everyone's concern. I would not want to buy a house with half-assed wiring in direct violation of NEC. When someone gets killed because of stupidity like this, it's a safety issue for the general public, because it may not be Ivan that winds up dead.

Reply to
trader4

And this is exactly why NOBODY should be taking electrical advice from you.

It is NOT "up to Ivan to figure out what he wants to do." It is up to Ivan to figure out how to install what he wants to install in compliance with the electrical code. In many places, the NEC has the force of law.

And it IS the concern of, among others, anyone else who might ever work on that circuit in the future.

If I was considering the purchase of a home in which an inspection turned up something like this, I certainly would refuse to close until the violation had been corrected. This is the sort of "material defect" that can scuttle a real estate deal.

Reply to
Doug Miller

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