Reading 120v on Neut but not on ground
Ok, what does this mean. I replaced a length of bad wire, about 7 feet that was J’d to a J-box. Of course when I replaced it I retied all the grounds together in the J-box. Turn on the power and I read 120v from not to neutral and 71v from hot to ground wire. I should be reading 120v from hot to ground. So….what would cause the difference?
Replies
The ground isn't.
What was evident in the old wire to lead you to replace it? Knowing this would help.
Well you're gonna love my answer. I wish I had a picture of it to show you, it'd speak for itself as to why I had to replace it. We're doing a remodel job for an HO. We had t open a wall to gain access to an electrical box containing two switches as we needed to rewire the switches due to changing them to 3 ways as part of our remodel job. When we opened the wall we found a buried J-box immediately below the box containing the two switches we were going to work on. This buried J-box had this romex wire going into it. The romex insulation had been stripped off the wire about 10 inches BEFORE it entered this J-box (no romex connectors anywhere either), thus only the single conductors were entering this J-box. The wires going OUT of the J-box were two single conductor black wires that went into the switch box to form two switchlegs that were what we were changing. There were no neutrals in the switchbox nutted together as you might expect. Instead we found the two neutrals were nutted together OUTSIDE of both the J-box and switch box, just hanging out in the wall. The wires going to the light fixtures were likewise stripped of the romex insulation 10" AFTER they left the switchbox. In other words, someone did a @#%# up job.
Showing this to the HO we decided to remedy the sitchiation and correct it and remove the J-box and do our rewiring as planned. We replaced the romex wire going into that J-box because it was wrong to have the romex stripped like that, and because we didnt' want to have a J-box to begin with (we're using the switchbox as a J-box as it should be), and because it's the right thing to do anyways. There was nothing wrong with the wire itself, it worked, but code-wise it was wrong and we needed an extra foot we didn't have. So replaced it. If at first you don't succeed, try using a hammer next time...everything needs some extra persuasion from time to time. -ME
Gotta go with Dan, the ground isn't.
A ground, that is.
SamT
Anyone who doesn't take truth seriously in small matters cannot be trusted in large ones either. [Einstein] Tks, BossHogg.
I guess I don't get what you mean....it's not a ground? Then what is it? I mean, it can't be anything else but, right? I guess maybe the safest bet is to trace the source wire all the way back to the panel and see if I discern anything along the way.If at first you don't succeed, try using a hammer next time...everything needs some extra persuasion from time to time. -ME
Obviously it is a sky, not a ground.
So what everyone means is that the connection of the ground wire is poor causing the low voltage reading. Check/tighten your connections should solve it. Good Luck
Could be a poor ground as others point out. Could be a neutral to ground fault related to the circuit you're fixing, causing the ground to go high. To find out if this is the problem: Turn that only that circuit's breaker off. Check the 'suspect' ground wire voltage (VOM, not shaker) to a known good ground like a cold water pipe- you probably have to use a long wire nutted to your 'suspect' ground. Be careful not to make your body part of the circuit, just in case.
If you get close to 50VAC (the difference of 120 minus the hot to ground reading you had of 71VAC) then it's a neutral to ground somewhere in the house. If you read O (or almost), then the ground is probably good. If you did get the zero, then check the resistance of that ground wire to water pipe connection, and if its a good ground back to the panel resistance should be less than a few ohms. (I did say KNOWN good ground, right?)
Assumptions:
Metal water pipes bonded to ground
No sub panel on the circuit you are fixing
A neutral to ground fault wouldn't cause this. In fact, absent a GFCI the fault wouldn't even be detectable. It's an open ground, plain and simple.
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
Edited 2/11/2007 12:15 am by DanH
As I said, it could be a poor ground. Considering the OP found some pretty bad work buried in the walls, confirming that the high ground condition does not exist due to a neutral-ground fault is a valid test. In the test sequence described in my message, the ground wire to water pipe Ohmmeter test checks/validates the "open ground" condition, does it not? And in the process, it also validates a low impedence path from:
The ground wire back to the main panel
The cold water pipe bond to groundFrom the OP's information so far, we know nothing of the condition of any of the ground wires in the residence:
- all of the grounds could be high
- it could be an old two-wire residence, and the only 3 wire romex is in the circuit he is working on, and the "ground wire" really isn't connected to anything at all in some yet to be discovered j-boxPersonally, I'd rather start with the quick test I prescribed than to start by checking ground to ground splices all the way back to the panel.And I truly do not understand your comment "In fact, absent a GFCI the fault wouldn't even be detectable." Really? Are you saying a VOM will not read a neutral to ground voltage or current?OR are saying that the lights will still light and the breaker won't trip with a n-g fault? If it's the latter, then I agree "the fault won't be detectable"- there's nothing to detect it. The breaker only protects the hot, and the lights don't care how their current gets back to the panel.The HO's new entertainment center will toast, but the dining room lights will still work, no problem.
> Considering the OP found some pretty bad work buried in the walls, confirming that the high ground condition does not exist due to a neutral-ground fault is a valid test.A neutral-ground fault would not cause a "high ground". What we have here is a LACK of connection between the purported neutral and ground wires, and given that the neutral is producing a reasonable voltage, it's about as certain as you can get that the problem is a disconnected ground.Checking resistance between the ground and a cold water pipe (don't give me code here -- this is a TEST, not a permanent connection) or some other spot that can be reasonably assumed to be ground will undoubtedly show a very high resistance, as will checking resistance between ground and neutral.
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
it could be an old two-wire residence, and the only 3 wire romex is in the circuit he is working on, and the "ground wire" really isn't connected to anything at all in some yet to be discovered j-box
We've done work on this house before. We recently replaced a two wire circuit of receptacles with a grounded circuit to grouind the receptacles. There is some residual 2 wire circuitry still present in the house but most of it has been replaced by prior "electricians." Electricians being an uncle (by marriage as I understand it) and an electrician that used to work for an oil company installing and servicing HVAC units in residential applications.
the J-box I ran the new wire to had all new romex in it and grounds tied together. The circuit then heads right back to the panel, so the assumption was made on my part that it's one of the circuits that has been replaced by prior elecrtricians. If at first you don't succeed, try using a hammer next time...everything needs some extra persuasion from time to time. -ME
If you have a tone tester this is the idea place to use it.Connect the generator from neutral to ground. Then go from box to box and along the cable to see where the tone stops or is greatly reduced.You can sometimes follow it in a finished wall, but not always. I am tlaking about the $70-90 Progressive/Greenlee/Tempo/Textron.http://www.stayonline.com/detail.aspx?ID=155Like this except for the the generator is the 77HP. Don't know the difference in performace between the 77M and 77HP. But the kit with the 77HP is what I got from HD about 2 years ago..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
"Turn that only that circuit's breaker off. Check the 'suspect' ground wire voltage (VOM, not shaker) to a known good ground like a cold water pipe-" Cold water pipes are not a trusted ground. And code prohibits using the Cold Water Pipe as a ground electrode except within 5 ft of where it enters the house and then only if the pipe is metalic and underground for at least 10 ft."then it's a neutral to ground somewhere in the house."THE NEUTRAL IS SUPPOSE TO BE TIED TO THE EQUIPMENT GROUND CONDUCTOR.The neutral bus is bonded to the ground bus at Service Entrance. Typically that is the main panel.That will hold if there is a sub-panel or not. Or if the service entrance has a ground electrode conductor run to the a water pipe ground electrode or not or if the water pipe is bonded to the ground electrode or not.What used to be allowed is for the equipment ground conductor to be connected to "near by" cold water pipes. The problem is that often later the metal pipe is replaced by plastic. And thus the EGS is no longer functional. That may have been what happened here.But based on the other things in this house it might be that the EGC some place in the circuit was never connected to anything..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Bill,
What would result in a potential of 71 V as the OP is describing? I would have thought that the measured potential would always be a multiple of 120 (i.e. either 120 or 240).
It means that the wire is not connected to anything and what is being "senses" is the open wire being capacitively couple to both the hot and neutral wires..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Thanks for the reply Bill, but it might be over my head. ;)
Could you elaborate on why the meter would register 71V if the ground is unconnected? Is it basically just sort of garbage reading?
"Is it basically just sort of garbage reading?"Yes.The meter has 10,000,000 ohm input impedence. So with the ground wire open it acts like a big antenna..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Thanks Bill.
you said "It means that the wire is not connected to anything and what is being "senses" is the open wire being capacitively couple to both the hot and neutral wires."I agree with the phantom voltage reading as the most likely indication of an open ground too, Bill. I get uneasy just waving my hand at that alone, in the case there really is more going on.
You missed the reference to the possibility of a 50V reading. Here's a quote, with the 50V part, from his post."Check the 'suspect' ground wire voltage (VOM, not shaker) to a known good ground like a cold water pipe- you probably have to use a long wire nutted to your 'suspect' ground. Be careful not to make your body part of the circuit, just in case.If you get close to 50VAC (the difference of 120 minus the hot to ground reading you had of 71VAC) then it's a neutral to ground somewhere in the house. If you read O (or almost), then the ground is probably good. If you did get the zero, then check the resistance of that ground wire to water pipe connection, and if its a good ground back to the panel resistance should be less than a few ohms. (I did say KNOWN good ground, right?)""I cut this piece four times and it's still too short."
Edited 2/11/2007 9:27 am by highfigh
A well meaning, but preposterous post.
You talking about my post or the one I quoted?
"I cut this piece four times and it's still too short."
The one you quoted. But you didn't say anything in your post, so no worries.
Onto my soapbox:You describe my diagnostic as "preposterous". In contrast to the industrial control/electrical business I retired from, I have found residential guys use their meters less and work faster. Borne out of necessity to stay employed, no doubt, as well as the simplicity of single-phase work. In factories, the three-phase, single-phase, DC, and computer communications landscape changes daily. Good luck finding a current wiring diagram, or trusting that a wire goes to where you think it should. Due to motor rotation direction and safety concerns, under my watch an unknown circuit never went live until it's meggered and/or continuity checked. We seldom deal with open grounds, however, due to metal conduit everywhere. Very poor grounds usually due to corrosion, yes. Certainly an earthing point at almost every machine and ground loops all over the place.So, my approach might not be what you expect in a residential environment, therefore "preposterous" in that sense. Thank you for acknowledging that it is well-intentioned.
My point was about the neutral to ground fault. If that were true, then the same potential would be present from hot to neutral as hot to ground, and probably be unnoticed even though it is an improper connection. This is because they are tied together in the main panel. If the ground is an open circuit, the DVM will sometimes indicate a fairly high voltage due to coupling of the conductors. The best way to test this problem is to use an incandescent test light, wiggy, or low impedance tester to avoid that problem.
I would venture a guess that the grounded wire is connected to an ungrounded circuit somewhere, or the grounds are pulled apart. Another thing is ground wires that are connected to heating ducts and water pipes which are no longer grounded.
I would venture a guess that the grounded wire is connected to an ungrounded circuit somewhere
That raises a question in my mind. If what you say is a genuine possibility, then when I test from the hot to the ground wire shouldn't I still get 0 volts? That is the ground may be wired into other parts of the same circuit but if somewhere it dead ends before it enters the main panel then it's simply that, a dead wire doing nothing. So how, in the possibility you raise, could it somehow measure any volts? If at first you don't succeed, try using a hammer next time...everything needs some extra persuasion from time to time. -ME
Well, a very high impedance meter is reading the voltage that is induced into the ground wire by its close proximity to the hot conductor. This voltage is induced by inductive and capacitive coupling. Some call it a phantom voltage. If you hook up a 60 watt bulb between hot and ground, then measure the voltage, you will see that it will read virtually 0 volts, if the ground is not connected to a real ground. A properly wired circuit will light the lamp, unless there is a GFCI, which would trip because there is current to the ground conductor.
I found the problem today. I don't fully understand it, but those on here helped me find the problem and may be able to explain it.
The problem was: Ahead of the J-box where I spliced in the new wire there was another Metal J-box. This J-box had a 2 wire circuit in it that ran directly back to the main panel. Thus, it's is not a grounded circuit. In this J-box Romex was spliced to the 2 wire circuit. The Ground for the Romex that later down the line was feeding my new wire, was simply wrapped around the screw that held on the metal cover plate for the J-box. In some form of twisted thinking whoever did this must've thought it would somehow ground the box, I dunno what they were thinking. The point is, the circuit wasn't grounded. It sucks, too, because there is only 20 feet of 2 wire cable from the panel to this J-box. All of the wire on THIS circuit had been upgraded to 12/2 but they didn't have enough fortitude to go and finish the job by running 20 more feet to ground the thing at the panel with new wire. Unbelievable.
Anyways, still with this arrangment I don't fully understand how I'd get any reading on the ground. To me it seems like it's a dead ground. But if I understand from prior posts, what I may be reading is stray voltage that finds its way BACK to the ground wire by virtue of the bonding in the electric panel. In effect, a loop of sorts is created because the neutral is bonded to the ground in the panel. Thus, a hot wire to ground reading is sorta tricking the meter and indirectly picking up voltage in the neutral wire, but on the ground. If this is the case then I'd never have guessed it in a million years and it only adds to my understanding in case I'd ever see this again. If at first you don't succeed, try using a hammer next time...everything needs some extra persuasion from time to time. -ME
what I may be reading is stray voltage that finds its way BACK to the ground wire by virtue of the bonding in the electric panel.
Willie, ya wanna freak out?
Take that 20' of 2 wire, throw it out sorta straight on the floor and measure the voltage from it to the new ground you're putting in.
Phantom voltages are only induced into a wire that is NOT connected somewhere to a hot, a ground, or thru a load to hot or ground. IOW totally open.
Although, technically, a really long wire with one end connected to ground can show some voltageSamT
Anyone who doesn't take truth seriously in small matters cannot be trusted in large ones either. [Einstein] Tks, BossHogg.
Take that 20' of 2 wire, throw it out sorta straight on the floor and measure the voltage from it to the new ground you're putting in.
I may a tad dense here....I'm not sure what you're saying to do exactly. It sounds interesting, that is you're trying to help me understand something here and I don't want to miss it. Are you saying to remove the 20' of 2 wire, replace it with the new 20' of 12/2 so that circuit is now grounded, and do what exactly with the 2 wire cable then?
Phantom voltages are only induced into a wire that is NOT connected somewhere to a hot, a ground, or thru a load to hot or ground. IOW totally open.
If I'm understanding you, a plain vanilla wire just laying out in the open will measure some kind of voltage? I"m not sure what you're saying here. How can voltage be induced into an unconnected wire?If at first you don't succeed, try using a hammer next time...everything needs some extra persuasion from time to time. -ME
"If I'm understanding you, a plain vanilla wire just laying out in the open will measure some kind of voltage? I"m not sure what you're saying here. How can voltage be induced into an unconnected wire?"Induced is a poor choice of words. That implies inductive coupling for which you need a closed path.What you have is capacitive coupling.http://en.wikipedia.org/wiki/Phantom_voltageIt looks like DanH has been at work. .
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Ugggh, ok I read the link, still confused. Is it saying that because there is a wire nearby that is carrying voltage (ther was another 2 wire circuit directly running beside, and parallel to the 2 wire circuit causing the ghost voltage) that due to the nature of electricity voltage is somehow transferred to the ground wire (the dead wire) making it appear to have voltage? It has nothing to do with the fact the neutral is bonded in the main panel at all is what I got in part from the link.If at first you don't succeed, try using a hammer next time...everything needs some extra persuasion from time to time. -ME
If I'm understanding you, a plain vanilla wire just laying out in the open will measure some kind of voltage?
Yes, provided the input impedance of the meter is high enough.
How can voltage be induced into an unconnected wire?
Short and simple and very broadly; Radio Waves, not necessarily in the AM or FM spectrum.
In our electricity filled world, the entire environment is filled with electromagnetic radiation, a fancy term for Radio Waves. Everything that can conduct, exclusive only of those things that are much smaller than the wavelength of any radiation around, will have currents in it. If those currents have no place to go they will create a potential at the leads of a high input impedance device.
Please note that if you connect a low impedance device of around 200 thousand to 700 thousand ohms, like your body, these voltages mostly, not always, will be so low as to be unreadable without very sensitive instruments. If you were to connect an microampmeter, you might measure 0.000...0001 amps.
AM, FM, TV, Satelite, Radar, Microwave ovens, cell phones, garage door openers; all use "Radio Waves."
A house that has been powered up, so to speak, is particularly filled with 60 cycle electromagnetic energy. There are typically several thousand feet of electrified wire acting as a transmitting antenna and any pair of wires, where one is electrified, will experience capacitive and or inductive coupling even greater than radiant coupling, although Radient coupling is always present everywhere in the US of A.
Radiant electromagnetic energy can be created by a voltage source, as when all the breakers are turned on, but no load is active, or by a current flow, as when there is a load running. Usually there are both voltage and current components in the source of the EM radiation.
The term Electromagnetic Energy as I'm using it here, includes all three forms, Capacitive coupling, Inductive coupling and Radiant coupling. Your boombox, or TV, only uses Radiant coupling from the station to your antenna.
If you want to get a headache looking at formulas, here is http://my.integritynet.com.au/purdic/basic-electronic-units.htm.
Basically capacitive coupling is area over distance the distance between themwhere Area is the mutual area between two conductors, ie, if on conductor is 6' square and the other is only 6" square, their mutual area is 6" square.
area_____distance
Inductive coupling between two straight wires is basically a function of mutual length over distance between them.
Length ______Distance
Aside: here is a downloadable EM reference tool: EM Formulary Reference ToolSamT
Anyone who doesn't take truth seriously in small matters cannot be trusted in large ones either. [Einstein] Tks, BossHogg.
This is still a work in progress: http://en.wikipedia.org/wiki/Phantom_voltage
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
Willie
85524.47 in reply to 85524.46
I found the problem today. The Ground for the Romex that later down the line was feeding my new wire, was simply wrapped around the screw that held on the metal cover plate for the J-box.
My whole house was wired that way ( 1950's ranch ) with 2 prong receptacles.
As the cloth covered romex entered and exited the J box's, the electrician wrapped the ground wire around the cable clamp screws inside the box. And the screws weren't even that tight!
I suspect this "Technics" was the accepted way of terminating grounds back then. Many of the houses in my neighborhood are the same way.
Bill
One basic thing that I have learned from trouble shooting is to ONLY work on ONE THING at a time.Keep all of the other variables alone and test one thing and work from there.I have learned that trouble shoot avionics systems to industrial (utility) control systems.Often from long distance and without complete specs on what all was in the systems. The techs would call me after changing a dozen things and no one would know what was what. I would start with some know condition and then get the results of that. Then make ONE CHANGE and see what affects that had.In this case we already knew the first problem. The ground was not connected to the neutral.That needed to be fixed. AFTER that was done then other problmes could be checked for..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
you said
"Cold water pipes are not a trusted ground. And code prohibits using the Cold Water Pipe as a ground electrode except within 5 ft of where it enters the house and then only if the pipe is metalic and underground for at least 10 ft."No where did I say that the cold water pipe is to be used in place of a driven earthing rod for code compliance. I just suggest the cold water pipe as an easy ground point to put the VOM probe on. Is the pipe a known good ground? I don't know, that is for the OP to decide. I'm just guessing it might be easier to get to than the nearest ground rod for the purposes of putting a VOM probe on a true ground instead of a floating one.But thanks for clarifying the point about a water pipe not allowed as an equipment ground for the readers who are not aware.I said: "then it's a neutral to ground somewhere in the house."you said "THE NEUTRAL IS SUPPOSE TO BE TIED TO THE EQUIPMENT GROUND CONDUCTOR.The neutral bus is bonded to the ground bus at Service Entrance. Typically that is the main panel."Thanks for making the code requirement clear. Perhaps it wasn't obvious enough, but when I am discussing a neutral to ground FAULT "somewhere in the house", I do not mean the n-g BOND at the main
panel.Next, I mentioned I'm assuming there is not a sub-panel involved in order to simplify the discussion. The reason I'm clarifying my assumption is that on some wacky electrical job, like this Wonka fellow is tackling, I would not be surprised to find a sub-panel with the neutral-ground bonded, instead of isolated as it should be. So I didn't want to go there, in other words.You said- "But based on the other things in this house it might be that the EGC some place in the circuit was never connected to anything."I agree.I believe your comments to my post are well intentioned, and you have no way of knowing my depth of code knowledge and electrical design experience. Your points certainly help a novice or DIYer from confusing my troubleshooting suggestions with code requirements.
This residence has a 200main and a 100a sub. It is unclear to me at this point until I investigate further if a ground loop condition occurs. I do not believe however, this circuit runs to the sub. The sub was installed to service the pool, baseboard heat, etc. So far the general lighting circuits have all been inside the main, since we've started doing work there that is.
Incidentally, the HO loves us, said we seem to be most knowledgable and are doing a good job. They characterized the other electricians they had there as "worried they were fly by nighters." When we showed the HO the jungled mess inside the wall we pointed out to her that A) it'd never have passed inspectoin that way, B) no romex connectors were used, C) not allowed to bury a J-box, and D) it's completely unprofessionial. If at first you don't succeed, try using a hammer next time...everything needs some extra persuasion from time to time. -ME
WillieWonka,
It will be interesting to follow up on this. Again, I agree with the other posters that you most likely are dealing with an open ground. I thought that I offered a more diagnostic approach that has the advantage of discovering other shortcomings in the house wiring.Since I made the "known good ground" stipulation and used the cold water pipe AS AN EXAMPLE these guys haven't let up on me. All I'm suggesting is that with pipe it is easy to physically see if it is bonded to the earthing rod or other valid (low resistance) equipment grounding point reference. Substitute something else for "cold water pipe", but I wouldn't be surprised if the pipe IS being used as the grounding point to the main panel. Maybe a rod was driven when the pool panel was put in.With your latest post, we now know that a sub-panel was installed and extensive work done without professional expertise. We also now know that the residence was two wire originally. Certainly there is plenty of work to be done and you have credibility and rapport with the HO. I'm hoping you will do them (and your business?) a big service and offer to inspect/repair the violations and most importantly any hazards associated with the pool electrical.When looking at the "big picture" with this residence the lighting circuit hot to ground issue you started the thread with is probably the tip of the iceberg. Simple open ground or not, in checking the H-G you took a step that many others skip because they assume new, shiny wire means their work is done. You also took the initiative to find out more. My hat's off to you.
Edited 2/11/2007 4:29 pm ET by lcdeyes
Yeah, I run a business doing home improvements and this is a contract we're working on. We'd never have discovered this issue if it wasn't for the fact that HO gave us more work adding can lights to their drop ceiling which necessitated the need to open up that wall.
We found a LOT of other botched wiring in the house. That is, we're renovating now a back porch that used to be just that. At some time in the past it was made into an enclosed porch and is now the family room with a drop ceiling. It was a peepoor job as it was. The ceiling only had R13 in it plus the ceil tiles. We find a LOT of J-boxes above the susp ceiling where there are no covers and MASSIVE amounts of wire stuffed into small J-boxes, the small octogon metal J-boxes. In some cases, so much wire was attempted to be stuffed in the boxes that they instead pulled the wires into the J-box and then pulled them out in front of the J-box and nutted them there and left them hanging. I'm not kidding you. We didn't fix those problems, and we really hadn't pointed them out to the HO. You'd think we would, and maybe we indeed should. We were instead focused on what the HO hired us to do, renovate and insulate the area more and put up DW walls.
As to your topic concerning the cold water pipe, I fully understood what you were saying. The point is you want to find a point of a true known ground and retest to ensure a positive test, thereby proving an issue exists with the ground wire.
In our area the inspector requires us to bond to an earth ground rod and to a cold water pipe where possible to do so. When not possible to do so we're made to run two ground rods 6 feet apart with a continuous solid #4 bare copper wire and of course the acorn nut.
We just completed a job where the home was on a well with the "plastic" well tubing coming into the pump inside the house. You obviously can't ground to the pipe before it goes into the foundation to the ground. But we were made to run 2 ground rods 6 feet apart AND he wanted us to bond to the nearest cold water pipe in the house. Thus the panel is bonded to the nearest cold pipe and to two ground rods. If at first you don't succeed, try using a hammer next time...everything needs some extra persuasion from time to time. -ME
"In our area the inspector requires us to bond to an earth ground rod and to a cold water pipe where possible to do so. When not possible to do so we're made to run two ground rods 6 feet apart with a continuous solid #4 bare copper wire and of course the acorn nut."The 2005 makes it clear that if you use a ground rod then two rods much be used uless they are tested to be less than 25 ohms. Apparently that has been the intent for a while from what I have read from some discussions. But in many areas it has been common practice to use just one ground rod as a sumpliment with a water pipe ground. Also the code calls out for a supplimentary ground electrode if the water pipe is used as a ground electrode. My guess is that is because in the future it can be replaced with plastic piping. The ground rod(s) are not the only way to supplimnet the water pipe electrode, but are the most common on residential retrofit. For new construction electrodes (can be the rebar) in footings is the best method."We just completed a job where the home was on a well with the "plastic" well tubing coming into the pump inside the house. You obviously can't ground to the pipe before it goes into the foundation to the ground. But we were made to run 2 ground rods 6 feet apart AND he wanted us to bond to the nearest cold water pipe in the house."This is a confusing area. The purpose of bonding the interior water piping (if metal) has nothing to do with the purpose of using the water pipe or ground rods for ground electrodes. The purpose of bonding is to insure that any metal in the house that one might come into contact with is at the same potential. Likewise the gas pipe and furance duct work is suppose to be bonded. But in those cases it usually through the EGC to the furances and gas appliances so that no separate wires are run.BTW, if the well casing is metal that makes a great electrode also..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Correct, that is always been my understanding of bonding to the cold water pipe, in case something in the plumbing would be electrified it has a way of getting back to the panel which is then properly grounded to cause the breaker to trip.
Ive been confused on this a few times. The last several years we've been told when there is public water you must run a ground to the point closest to the water meter before it goes out into the ground. But I oft never saw the point. That is, sure, if you had a ground at the end of a copper plumbing line and grounded to that location at the end, and later replaced a section with PVC, you'd have interupted the ground getting to the ground via the water pipe. But in that scenario, you COULD still get an electric shock by other parts of the copper plumbing system that are isolated from the cold water pipe ground wire by virtue of the PVC splice in the water line. The degree of "caring about this issue" confuses me, on one hand we're concerned about it, buton another we don't codify it that if you do that you must run another ground wire to the section of copper plumbing you've isolated.
To clarify what I mean, in the prior job we had to bond to the nearest water pipe which happened to be at the end of a plumbing system that is all copper. Right after water comes out of the pump it branches off to a kitchen, all in copper plumbing. Thus, if something in the kitchen plumbing became electrified it'd go thru the system to the ground clamp then ground wire then to the panel, trip the breaker, and out thru the ground rod. so far so good.
But then say the HO replaces a section of the cold pipe with PVC between the kitchen copper plumbing and the water pipe clamp. Now the kitchen copper plumbing is isolated from the ground. If the kitchen plumbing gets electrified a potential deadly shock could occur. Yet it seems to be allowed. If at first you don't succeed, try using a hammer next time...everything needs some extra persuasion from time to time. -ME
I agree in concept, but I am not that sure that it is a realy problem. Depends on the total age and repairs on the system.The code specifically calls out bonding around an water meter when in the house. I need to read and reread the code and look at the handbook, which has some explaintions to see if you are suppose to bond around a section of metal pipe that has been replaced by plastic or not.One of the problems is that work would be done by plumbers and not electricans and thus never done.Now in a modern house that won't be a problem as the garbage disposal and the dishwasher each have their own EGC and will ground anything on the kitchen end of the plastic splice.Where you can get into trouble is where you have a house that was built before EGC's (I think in the middle 70's) and where EGC for the dishwasher or GD was connected to the nearest cold water pipe. Now that was allowed until the mid 80's, but I still here people saying that it is OK..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
The ground is either "completely open", that is connected to nothing. Or it has a very high resistance connection. Assumen a 10 meg ohm meter the resistance would be about 5 megs.For an EGC that is OPEN.What other problem would give the same symptom?What does measuring from the the EGC to a cold water pipe prove? NOTHING! A EGC could be wired correctly and that test fail.We already know that the EGC has problems and testing against the cold water pipe just brings in additional unknows and adds confusion.The break in the EGC still needs to be found. And that means checking connections until you find the bad/missiing one (or bad cable).But that does not mean checking everyone. Binary sorting can be used to reduce the number checked. But in house wiring, specially one that has been modified, it might not be easy to layout the path to use binary sorting..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
I usually quit checking after the problem has been found, not all the connections!
But... I would be inclined to check every electrical connection in this house from my understanding of the history.
"THE NEUTRAL IS SUPPOSE TO BE TIED TO THE EQUIPMENT GROUND CONDUCTOR."
When I wired my house, the inspector who came to look at the electrical rough specifically requested that I replace the metal tie bar in the main panel, which connects the ground bar to the neutral bar, with a plastic one.
While this guy was a 'building inspector,' his forte was electrical. I cannot say for sure whether it was his own personal preference, or an actual code issue, but I spent too much time trying to find a plastic tie bar to replace the metal one. He told me they were available, but ultimately I ended up leaving it off entirely.
I think his reasoning was that if the neutral wires were to ever be pressed into service (presumably by accident), they wouldn't energize the ground wires. This WAS several years ago, so maybe things have changed. Or maybe I obtained completely dangerous, erroneous information. Ask the pros : )"It depends on the situation..."
When I wired my house, the inspector who came to look at the electrical rough specifically requested that I replace the metal tie bar in the main panel, which connects the ground bar to the neutral bar, with a plastic one.
That's not right, in most areas. The ONLY exception I have seen is when the tie point is at the meter socket rather than the main service panel, and that is rare (but determined by the utility).
The point is that the ground and neutral are to be tied together in EXACTLY one place, most commonly the service panel. The tie is required by NEC, the place of the tie is usually determined by the utility or the municipality.
If this were a SUBpanel, what the inspector said would be correct, but not for the main panel.
"THE NEUTRAL IS SUPPOSE TO BE TIED TO THE EQUIPMENT GROUND CONDUCTOR."But at one and only one point and that at the service enterance. Typically the main panel is the service entrance. And ground electrode conductors (the one to the ground rods and cold water pipe) connect at the service entrance (or in the meter).But some installation have a disconnect near the meter and that is the service entrance. It then feeds one or more panels in the house. Thoses panels are technically sub-panels and have to wired as such.Now the neutral is bonded to the earth ground at the transformer. But it should also be done at the service entrace is help discharge any surges that might be induced in the wires from nearby lightining strikes."When I wired my house, the inspector who came to look at the electrical rough specifically requested that I replace the metal tie bar in the main panel, which connects the ground bar to the neutral bar, with a plastic one."The best thing that I can say about that inspector that there was a failure to communicate.Some panels have two bus bars. Typicall one on each side. One is insulated. And metal bus are strape goes between then. Either the 2nd bus is mounted directly on the metal case or the strap is screwed to the case. With the strap in place the two buses are connected to gether and bonded to the case. If the strap is removed there is no reason to replace it with a plastic one.The other style has one bus bar that is isolated, but has a green bonding screw. And that bonds it to the case. For a sub-panel remove that screw and use the bus as a neutral bus.Then you add separate ground bus bar kit. The "kit" is just the bus bar and screws that bolt them to the case..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
With the goofiness of the previous wiring job, I wouldn't take anything at face value. Did you try checking the potential between the neutral and the "ground", too?
I'd check the potential of ALL of the wires against a KNOWN ground. That should at least troubleshoot things to the point where you can identify which wire is not responding the way it should.
No, I didn't check potential between neutral and ground, I could do that, that would be an interesting checkIf at first you don't succeed, try using a hammer next time...everything needs some extra persuasion from time to time. -ME
I can't figure out why you'd be getting 71 V.... but it occured to me that 71 is roughly one third of 220. Perhaps that's a clue. Can it be a phase thing?
I doubt it, I got 120v across the black and white. If what you're suggesting is true then I'd still get 120v black to ground, even on a 240v circuit.If at first you don't succeed, try using a hammer next time...everything needs some extra persuasion from time to time. -ME
71V would be showing if the connection isn't tight. If the ground were floating free, there wouldn't be any reading.
Tighten the ground & it should be good.
"71V would be showing if the connection isn't tight. If the ground were floating free, there wouldn't be any reading."Here we go again.Read the rest of the thread..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
check your test instrument on a known supply & make sure there is no 9v battery inside it
"check your test instrument on a known supply"He did. That is how he got the 120v reading from Hot to Neutral."& make sure there is no 9v battery inside it". I am sure that there is one (but it might be a several AA batteries. So what?.
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Ok, what does this mean... I read... 71v from hot to ground wire.
It tells me two things:
A $10 Radio Shack Analog meter will measure correctly.
SamT
Anyone who doesn't take truth seriously in small matters cannot be trusted in large ones either. [Einstein] Tks, BossHogg.
You are using a high input impedance digital meter.
A $10 Radio Shack Analog meter will measure correctly.
I'm puzzled by your comment - and not sure what you think an analog meter will measure differently.
By design, ANY voltmeter should have a high input impedance. While older analog meter typically do have a bit lower imput impedance, say 1M vs 10M, it still should have a high input impedance.
The thing we don't know about the OPs situation is if the circuit is open, or if it is connected to something else, or if it has a high resistance connection to a 120 V wire. I have seen all three.
This is a great application for the neon bulb testers - if there is a "real" 70 V difference between the wires, the bulb will light (assuming sufficient current).
Based on past experience, here is a wild guess (but one I have seen often) - the wire is shorted to the furnace control wiring or thermostat wiring.
Analog especially cheap analog meters are lower impedance. 5000 ohms per volt on AC is typical for a good one. So that is 1.5 Meg ohm (on 300VAC scale) versus 10 meg ohm on a digital. Then a 70 volt reading on the DVM would be about 10.5 VAC or less on an analog meter. That would barely nudge the needle.
A true analog meter, as opposed to a transistor input meter, is actually a current meter in parallel with a network of resistors in series.
The voltage to be measured is applied across the resistor network and the scale selector switch places the current meter across the appropriate resistor in the network, such that the current flow thru the meter is right for the voltage scale being used.
Ohms' Law states that E=IR or voltage equals current times resistance. By measuring the current thru a known resistor, one knows the voltage across that resistor. Applying Khirkoffs' Law to the resistive circuit composed of the current meter and the VOMs resistive network, the manufacturer can calibrate the scale to accurately indicate the measured voltage.
The current flow thru a High Input Impedance Meter (HIIM) from input lead to lead with a low voltage applied can literally be measured in electrons or micromicroamps.
Every power source, be it a battery, a capacitor, the generators at Hoover Dam, and even the space between the radio station and your car antanna, have an internal resistance (reactance.) As long as the resistance of the load is significantly higher than the internal resistnce of the source, there will be no voltage drop in the circuit.
You can test this by plugging in a high amperage saw or heater to 200' of 14 ga extension cord. The saw sees the plug in end of the cord as it's source. Measure the volts at the saw's source and it'll read 120V because the saws' resistance is infinate until you pull the trigger. Once you turn the saw on, its' resistance drops to ~20 ohms, not very many times greater than the resistance of 200' of 14ga.
The internal reactance/resistance of the source of Phantom Voltages aproaches several thousand ohms. My Micronta AVOM has an input impedance of only 3Mohms on the 300V scale.
It just overloads the source of Phantom Voltages and drops them down to unreadable. A good DVOM has such a high resistance that it does not overload the PV source.
Consider this analogy; Phantom voltages are like 8 AAA batteries in series. You can measure 12 volts with a VOM, but they sure won't run your cars' starter. The starter being equivalent to an AVOM.SamT
Anyone who doesn't take truth seriously in small matters cannot be trusted in large ones either. [Einstein] Tks, BossHogg.
A sensitive VOM has the meter in SERIES with the resistor. Placing a resistor in parallel with the meter makes it less sensitive.
For current measurements the meter and resistor are placed in parallel.
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
What in heck is a "sensitive" VOM? Does it cry when you yell at it?
Bill, I think yer rite. 42 it is.SamT
Anyone who doesn't take truth seriously in small matters cannot be trusted in large ones either. [Einstein] Tks, BossHogg.
I just reread yoour post. This time I'll try to answer your questions.
A $10 Radio Shack Analog meter will measure correctly.
I'm puzzled by your comment - and not sure what you think an analog meter will measure differently.
An analog meter will measure very high internal impedance sources like capacitively coupled Phantom Voltages differently than a Digital meter will.
By design, ANY voltmeter should have a high input impedance. While older analog meter typically do have a bit lower imput impedance, say 1M vs 10M, it still should have a high input impedance.
I have two AVOMs, one 20yo, other 2yo. Both show 10K ohms/volt. What that means is 10K times full scale volts, or 3M ohms if using the 300 volt scale< P>
A DVOM can reach 109 ohms input impedance. Further "High" is a relative term. A voltmeter should have a high input impedance compared to the resistances expected in the circuit being measured input impedance. Measuring an electron plasma with superconducting leads, your voltmeter would only need a couple of ohms impedance to work.
An AVOM only has a low impedance (1x104/volt)compared to a DVOM (1x109/volt.) A DVOM is low impedance compared to an Electrometer (>1015ohms)
SamT
Anyone who doesn't take truth seriously in small matters cannot be trusted in large ones either. [Einstein] Tks, BossHogg.
"This is a great application for the neon bulb testers - if there is a "real" 70 V difference between the wires, the bulb will light (assuming sufficient current)."How much current goes it take to cause an NE-2 to glow?I have can make one the neon tester glow by putting one lead on the hot and holding the other in my hand and not being grounded. True, it is not near as bright as when connect directly across 120 and only one of the electrodes in the NE-2 is lite. But to someone that knows that when it is connected to 120 the test lights then this lite. That would give them false sense that they had a ground when the ground wire is completely open."Based on past experience, here is a wild guess (but one I have seen often) - the wire is shorted to the furnace control wiring or thermostat wiring."A wild guess should be based on some reality.That statement should be called wild fantasy. There was no mention of a furnace in this problem..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
There was no mention of a furnace in this problem.
Typically, this situation arises when the wire for the outside unit (AC or outside unit on a heat pump, for example) runs over top of the duct - a very common situation, at least around here in new construction. The installer pulls on the wire to straighten it before wiring the outside unit, and the duct, a nail point, etc. cuts into the control wire and shorts it to the duct.
I see this situation at least a few times a month. It's much more common than I would have ever imaged. The first one took a while to track down, now I know the symptoms and know to look for it - which is why I mentioned it here, since the described symptoms can match the OPs description.
The symptoms are similar to what the OP posted - a voltage is present on the neutral or ground. More typically, this problem is discovered when there is a voltage present on the ductwork, and some helpful soul decides the ductwork needs to be grounded. So maybe it's not all that similar to the OP's situation, but I still wanted to throw this in, for others that might read this thread in the future. It's a weird situation, but it happens.
How much current goes it take to cause an NE-2 to glow?
Typically around .3 mA to 1 mA, depending on the particular bulb. In other words, more than you are likely to see due to capacitance, inductive coupling, or other sources of phantom voltage
I have can make one the neon tester glow by putting one lead on the hot and holding the other in my hand and not being grounded.
This statement concerns me. PLEASE be careful, especially if you do not really understand this stuff. The bulb lights in that case because you ARE grounded. Keep in mind that we are talking about an AC ground, not a DC ground. A VOM won't measure it, but there is an AC connection (which is why special test equipment is required to test ground rods). Either way, you will be just as dead. It is unsafe to connect yourself into a power circuit under ANY circumstances, IMHO.
Given sufficient voltage to break down the contact resistance of the skin (typically 20V or so, less if you are sweaty, well hydrated, or have naturally lower resistance), very small currents can be fatal.
Edited 2/16/2007 9:04 am ET by woodturner9
"The bulb lights in that case because you ARE grounded. "It is called capacitive coupling. That is what this who discussion was about."The installer pulls on the wire to straighten it before wiring the outside unit, and the duct, a nail point, etc. cuts into the control wire and shorts it to the duct."How in the H*LL does a short in the control wiring for an AC unit cause the symphtoms reported in this case.If was clear from the first message that he had an open ground..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Neon testers will light if you touch one end to hot and hold the other end in your hand. Very susceptable to phantom readings.
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
Neon testers will light if you touch one end to hot and hold the other end in your hand. Very susceptable to phantom readings.
I agree with the observation - that the tester will light - but not the conclusion that it is a "phantom reading". The tester lights because the body is completing the circuit. If it is a "phantom" voltage, there will be insufficient current flow to light the tester. Phantom voltages will provide very low current, in the micro amp range, not the milliamp range.
And what is the body attached to?
I've seen the neon testers light on unconnected wiring.
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
And what is the body attached to?
The body completes the circuit to "true" earth ground. It's a high impedance path, but the current is low, so the IR drop is small.
I've seen the neon testers light on unconnected wiring.
So have I. But there has to be SOME source of current and voltage for the bulb to light. If you just connect the testor to a completely unconnected piece of romex, it won't light. If the hot is active and the neutral and ground are open, the bulb will light if it can find some return path (like your body, because you are holding one lead).
While it's possible to get enough inductive coupling in a wire to light the bulb, in my experience that's very unusual, particularly in residential wiring.
Well, my experience contradicts yours, and I trust my experience more.
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
Well, my experience contradicts yours, and I trust my experience more.
SO you are saying that if I take a 1 foot piece of romex, unconnected to anything, lay it out on the ground, and hook a neon tester to it, the tester will light? Do you live under a high tension tower? :-)
If that's your experience, I disagree, and I do trust my experience more.
No, I never said that. But if you take a 50-foot piece of romex, wire hot and ground properly but leave neutral disconnected, the neon light will light weakly when you touch the neutral and either hot or ground.
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
But if you take a 50-foot piece of romex, wire hot and ground properly but leave neutral disconnected, the neon light will light weakly when you touch the neutral and either hot or ground.
That makes more sense - glad we cleared that up. I agree with that - it's likely in that situation that there will be enough inductive coupling to light the bulb, at least weakly.
That's a little different situation than holding one lead of the tester in your hand, though, which is what another poster said. In that case, it's the body providing a weak path to ground, but it still lights the bulb weakly.
It's capacitive coupling, not inductive. For induction there must be current flow, and there is none in the scenario I described.
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
It's capacitive coupling, not inductive. For induction there must be current flow, and there is none in the scenario I described.
Current flow is also required to light the bulb and for capacitive coupling.
Recall that the current flow through a capacitor is C dv/dt. So if there is a constant voltage, there can be no capacitive coupling. If there is a voltage change, there is current flow.
The current flow produced in this situation is vanishingly small. Maybe someone who isn't using a laptop with rapidly diminishing battery power can look up the formula for induction in parallel wires and find the current needed to induce, say, 10V in 100 feet of romex. I'm pretty sure it's in excess of 100A.
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
I could not find a curve on the NE-2. But I did find that if fires at 65 volts. And normal operating current is 0.3 ma.But an NE-2 in series with a 2.2 meg resistor across 120 VDC will not keep the bulb fired. But add a cap and it is a relaxation oscillator.http://www.tinaja.com/glib/muse136.pdf.
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
But add a cap and it is a relaxation oscillator.
That cap is pretty big compared to what you are likely to see in house wiring. .047 uf vs 20 to 100 pF.
Never said that it was.Was trying some the range of currents that an NE-2 works on..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Depends on the load on the second wire. If it's open on both ends, you will see a high voltage with minimal current flow thru the primary. If it's close enough to the primary, you will see a high capactive induced voltage.
Put even a high resistance load on the second wire and you won't see hardly any voltage with out a lot of current in the primary.
briefly speaking.SamT
Anyone who doesn't take truth seriously in small matters cannot be trusted in large ones either. [Einstein] Tks, BossHogg.
Believe me, I don't want to unnecessarily lengthen this thread, but I'm not so sure that the neon tester lights when you hold one lead and touch the other to hot because your body is 'a high resistance path to ground', because it works even if you're standing on a fiberglass ladder wearing rubber soled shoes. Someone explain that to me, please.BillEdited 2/22/2007 2:04 pm ET by PGproject
Edited 2/22/2007 2:05 pm ET by PGproject
because it works even if you're standing on a fiberglass ladder wearing rubber soled shoes.
EVERYTHING is a conductor, and an insulator - the terms are not precise. We term a conductor that has "a lot" of impedance an "insulator".
The bulb needs current to light, so there must be a complete circuit for the bulb to light. There are several possible sources of the voltage and current required to light the bulb. One is the high resistance path through the body, through the fiberglass ladder, to earth ground.
Another possibility is that the body is acting as an antenna and picking up RF radiation - that's why a flourescent light bulb will light under a high tension tower, with no connections.
The key to this scenario is that you must touch the lead before it lights - that's the evidence that the body is completing the circuit, so that the high impedance path through the body, ladder, etc. is the cause. Now, that assumes our stipulation that the bulb will light if you are standing on that ladder. I haven't tried that, but my suspicion is that it will not, because the return path is too high impedance to provide enough current.
Another option is electrostatic fields, which behave somewhat differently that conventional wisdom suggests. An example is the shock you get when you touch a metal object in the winter. However, the discharge to light the bulb would likely dissipate this energy, so if the bulb stays on, that is not the cause.
I assure that it lights no matter where, or what upon, you stand. It works when I'm in rubber soled boots on a linoleum over plywood floor on the third floor.Bill
It is capacitance.Normally you thing of a capacior as two parallel plates separated by a dielectrice (which can be the air).In this case the body is one plate and the ground and neutral conductors and all of the other grounded metal in a house (copper pipes and metal ductor being most common) is the other.http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=737028"Abstract
A standing human body insulated from ground by footwear and/or floor covering is in principle an insulated conductor and has, as such, a capacitance, i.e. the ability to store a charge and possibly discharge the stored energy in a spark discharge. In the human body, the human body capacitance (HBC) is traditionally chosen as 100 pF. However, a simple geometric model seems to suggest considerably higher values. A series of experiments, where the capacitance of standing persons were determined for various combinations of footwear and floor coverings, gave values in the order of 100-150 pF when the capacitance was determined by an AC-bridge measurement, but 200-400 pF when the traditional static charge-sharing method was used. Further experiments indicate that the two methods give the same result when the electric flux is well located in a dielectric other than air, but that the static method leads to higher values when a substantial part of the flux extends itself through badly defined stray fields. Since the concept of human body capacitance is normally used in a static (electric) context, it is suggested that the HBC be determined by a static method. No theoretical explanation of the observed differences is presently at hand".
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
It is capacitance.
There must be current for the bulb to light and stay lit. For current to flow in a capacitor, there must be a changing voltage.
Where do you think the changing voltage is coming from? The 60 Hz AC voltage is too low of a frequency to pass through the capacitor, for any range of capacitance likely to occur under the situations we are discussing.
Here is another question - think about clouds and lightning. How is that situation different from or similar to this situation? Hint: clouds and the earth form a large capacitor - with no current flow, so no "bulb lighting". Lightning is when the potential exceeds the breakdown voltage of the air, and the lighting bolt fires - briefly - which discharges the capacitor, so the lighting stops (until the charge builds up enough again).
If the tester example were capacitive coupling, the light would blink on, then go off when the capacitor discharges.
Hence the result that it is a leakage path through the body, rather than capacitive coupling.
We are talking electron flow here, 50 microamps more or less. Not what we normally think of when we talk of current in a house.
The human body can act like a sump for this very small electron flow (<=417 picoampseconds) per half cycle, the electrons flow into the body and out for a total average body voltage potential change of picovolts.
Thus, it acts like a capacitor plate.
Plus, there ain't no such thing as a perfect insulator.
SamT
Anyone who doesn't take truth seriously in small matters cannot be trusted in large ones either. [Einstein] Tks, BossHogg.
We are talking electron flow here, 50 microamps more or less.
50 uA sounds about right for the current flow. Problem is, as noted previously, it takes 300 uA or more to light the bulb - 50 uA won't light the bulb. So if we only have 50 uA, that can't be what is lighting the bulb => so it can't be capacitive coupling lighting the bulb.
"50 uA sounds about right for the current flow. Problem is, as noted previously, it takes 300 uA or more to light the bulb - 50 uA won't light the bulb. So if we only have 50 uA, that can't be what is lighting the bulb => so it can't be capacitive coupling lighting the bulb."WRONG!Where did you get that it take 300 uA to "light" the bulb.Here is what I said."And normal operating current is 0.3 ma."That is NORMAL or the design operating current. Not MINIMUM.And as I said the I see is not normal operation of the bulb. Only one of the electrodes is lite and then only partially.But to some one that is only looking for it to be lite or not it would be lite.I would not be surprised that it is not in the neighborhood of 50 uA. Sounds about right..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Where did you get that it take 300 uA to "light" the bulb.
From testing a testing - hooked it up to a curve tracer.
Took 300 uA to make the bulb visible in normal room lighting, 200 uA to make it visible in a dim room.
Still, regardless of the current required for a particular bulb, if it were lighting due to capacitive coupling, there HAS to be a changing voltage. The 120 VAC won't do it - those capacitor values are open circuit at 60 Hz. So it CANNOT be capacitive coupling.
Still, regardless of the current required for a particular bulb, if it were lighting due to capacitive coupling, there HAS to be a changing voltage. The 120 VAC won't do it - those capacitor values are open circuit at 60 Hz. So it CANNOT be capacitive coupling.
Where you getting non-AC voltage in a house?SamT
Anyone who doesn't take truth seriously in small matters cannot be trusted in large ones either. [Einstein] Tks, BossHogg.
Where you getting non-AC voltage in a house?
I'm not. But house AC is 60 Hz, and a small capacitor looks like an open circuit at such low frequency.
For reference, the .01 uF or less of capacitance we have been discussing looks like an open circuit for frequencies below a MHz or so.
Oops! Never mind. Reading too fast.
Again.SamT
Anyone who doesn't take truth seriously in small matters cannot be trusted in large ones either. [Einstein] Tks, BossHogg.
For reference, the .01 uF or less of capacitance we have been discussing looks like an open circuit for frequencies below a MHz or so.
No it doesn't!
It does look like a high reactance, but it most definately is not an open circuit. No more than a 20 Meg ohm resistor looks like an open circuit to 100 volts.
You need to quit thinking in terms of ohms, amps, and microfarads, and start thinking in terms of megohms, microamps, and picofarads.
When you get down to the currents involved in glow lamps, there is no such thing as an "Open circuit."
There's only too high a resistance.
I suspect that in my experiment I was actually seeing a 50ua average flow. That what was happening is that when the voltage was above the sustain level more current flowed, but was cut off for the greater part of the cycle.
With induced, or Phantom, voltage, the voltage would drop below the sustain level as soon as the breakdown voltage was reached and current flowed. Because of persistance, these tiny, 120 times a second, pulses look like a dim continuous glow.
Heres an intersting table on resistivity I just found. Take a look at shellac or parafin.http://www.1911encyclopedia.org/Electric_conduction
Substance.
Resistivity.
Tempera-
ture
Cent.
Mega-
megohms
per c.c.
Megohms
per Quad-
rant-cube.
Bohemian glass. .
61
.061
60°
Mica
84
.084
20°
Gutta-percha. .. .
450
45
24°
Flint glass
1,020
1.02
60°
Glover's vulcanized india-
rubber
1,630
1.63
15°
Siemens' ordinary pure
vulcanized indiarubber
2,280
2.28
15°
Shellac
9,000
9.0
28°
Indiarubber
10,900
10.9
24°
Siemens' high-insulating
fibrous material
11,900
11.9
15°
Siemens' special high-
insulating indiarubber .
16,170
16.17
15°
Flint glass. .. .
20,000
20.0
20°
Ebonite. ... .
28,000
28
46°
Paraffin. ... .
34,000
34
46°SamT
Anyone who doesn't take truth seriously in small matters cannot be trusted in large ones either. [Einstein] Tks, BossHogg.
For reference, the .01 uF or less of capacitance we have been discussing looks like an open circuit for frequencies below a MHz or so.
The impedance of a capitor is 1/(wc), where w=2*pi*f
So, using 60 Hz and 100 pF, we see that the impedance is 26.5 Mohm - essentially an open circuit.
Given 120V, the current flow is I=v/r, or 4.5 uA - not nearly enough to light the bulb, yet more proof that it CANNOT be capacitive coupling.
With induced, or Phantom, voltage,
I agree the cause is INDUCTIVE COUPLING (i.e. induced voltage) - it's the "capacitive coupling" that isn't correct.
But for inductive coupling you have to have current flow. Where is the current flow??(FWIW, a neon light can "ignite" at voltages as low as 25V, especially if a source of UV light is in the room to provide excitation.)
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
My roommate in college had a 2 oz excedrin bottle filled with dirt.... and a wire sticking into it connected, yup, to the "ground" terminal on his stereo...
But for inductive coupling you have to have current flow. Where is the current flow??
It is induced through the interaction of the B fields (e.g. magnetic fields) caused by the flow of current in a wire.
Every wire that has current flowing through it creates a magnetic field around it. Other conductors within that magnetic field with have voltage induced on them. That's how a transformer works - but the same effect occurs with just a wire.
BOTH inductive and capacitave coupling require voltage and current flow. However, the inductance in a wire is relatively larger than the self capacitance, so that the inductance between pairs of 50' wires can be enough to provided enough current to dimly light the test bulb.
But the high resistance path through the body is still the most likely cause of the dim lighting of the lamp, in most cases.
WHAT FLOW OF CURRENT??? You see the neon light effect when no significant current is flowing in the wires. And I suspect you'd need in excess of 100 amps (if not thousands) to induce the requrired 25-50V in the unterminated wire in a typical 25-50 foot run.
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
And I suspect you'd need in excess of 100 amps (if not thousands) to induce the requrired 25-50V in the unterminated wire in a typical 25-50 foot run.
Well, it's easy to calculate.
B=uI/(2*pi*r)
r is the distance from the wire, so if we say r=3 mm:
B=uI/(2*pi*.03)
But here is a calculator to do it for you:
http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/wirfor.html#c1
If you play with it a bit, you find that a 100 uA current at .003 m (i.e. 3 mm) separation easily produces the required voltage
'Splain to me how you plugged numbers into that calculator to get a voltage out.
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
Dan, SamA while back one of the participants of this thread, and it was not me or you two, claimed that he make a two terminal device where the current into one terminal was different than the current out the other one.At that time I realized that he was not wrapped to tight.At that time I realized that futher dicussion was pointless.I have come to the same conclusion in this thread, for the same reasons..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
two terminal device where the current into one terminal was different than the current out the other one.
That's got Kirkhoff spinning in his grave (|:>)SamT
Anyone who doesn't take truth seriously in small matters cannot be trusted in large ones either. [Einstein] Tks, BossHogg.
Which is fair, because Kirchoff always kept me spinning.
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
two terminal device where the current into one terminal was different than the current out the other one.
That's got Kirkhoff spinning in his grave (|:>)
Wow - we agree on something!!
By definition, the sum of the currents into a node must equal the sum of the currents out of a node - that's Kirkhoff's law in layperson's terms.
I wonder which post Bill thought was saying that? I sure didn't say that.
ahem.........it's ...Kirchhoff, or sometimes Kirchoff, just not Kirkhoff, unless you guys have some esoteric text with an archaic spellingwe now return to our never ending hi-jacked thread....:).
.
.
., wer ist jetzt der Idiot ?
http://forums.taunton.com/tp-breaktime/messages?msg=83852.5"
From: woodturner9 Jan-8 2:06 pm
To: BillHartmann (5 of 18)
83852.5 in reply to 83852.4
"Your tester should trip a GFCI, even if the ground is not connected."How?As I explained, a GFCI responds to either an imbalance between the hot and neutral or a current flow in the ground wire (or both). In the OPs configuration, the imbalance is what identifies the ground fault (because there is no "real" ground).A tester works by creating this imbalance, which will cause the GFCI to trip. There are several ways to do it, but the point is that the tester creates the imbalance that simulates a ground fault.".
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
"Your tester should trip a GFCI, even if the ground is not connected."
I'm sorry, I thought that confusion had been resolved in the other thread.
Let me try again. As I said, a GFCI trips for two reasons:
1. The current in the hot is different than the current in the neutral by more than a threshold (typically 5 mA).
2. There is current flow in the ground greater than a threshold (typically 1 mA)
There are several ways to create these conditions in a tester. The second is easy - connect a neon test bulb between the hot and the ground.
The first is the more difficult one. One way is the way I think you understand - use a resistor network to split the current from hot to neutral and a separate ground from the receptacle under test (so that you are not tripping due to #2, which would be the case if you used the ground on the receptacle).
Another way, which appears to be the source of confusion, is to provide addition current or discharge some current to another path. Recall that EVERYTHING has reference to true earth ground, though it is typically very high impedance. An op amp has a high impedance input, so it can sense this ground potential and generate a low impedance source voltage at the earth ground potential level. So you essentially get the earth ground without a wired connection to it. Once you have the earth ground, you can electronically mimic the resistor network described above.
Op amps require power, however, so these testers often have a battery. However, a battery is not an absolute requirement - there are tricky ways to integrate the voltage from the hot, store it in a capacitor, and briefly display on a low current display such as an LCD before the capacitor fully discharges. But most of them just use a battery.
To recap, one can make a GFCI tester that does not require a physical ground connection. It's still a 3 terminal device that satisfies Kirckhoff's laws, though - it's just that the third terminal is not a physical connection.
Edited 3/1/2007 1:00 pm ET by woodturner9
(Big capacitor in series with a resistor) across hot to neutral.
Resistor size = 120/(tripping current + 10%)
Ka-click!SamT
Anyone who doesn't take truth seriously in small matters cannot be trusted in large ones either. [Einstein] Tks, BossHogg.
I lost interest in this thread a while back, but I want to weigh in here to retard the spread of incorrect information.
The requirement for a GFCI (a device intended to provide protection against shock or electrocution) is that it trip at 6 mA, +/- 1 mA. There is a time criterion also, and I can't recall it, and am not going to shoot from the hip and possibly pass on bad information. Even if I disclaim it.
A GFPE device (ground fault for protection of equipment) typically has a trip setpoint of 40 mA. The new AFCI circuit breakers have such GFPE protection built in.
Any standard GFCI device that's UL-listed compares current in to current out (on the ungrounded and the ungrounded condictors, respectively, for a 120V circuit). More than a 6 mA difference, and it opens the circuit.
SO that this post is more than just a correction, here's an interesting point to be aware of when troubleshooting branch circuits that may have a GFI in them: GFCIs also have an injector coil that impresses a minute voltage on the neutral of the protected side, so that the device will trip if there's a ground fault on the neutral, even if there's no current in the circuit. If there's a leakage path, the impressed voltage will produce current and the imbalance will trip the GFI. The injector coil is basically some turns around the neutral, with this "primary" connected to the hot and neutral upstream of the GFI protection. The neutral is the secondary.
What's the implication when troublehooting? It means that if there's a GFI in the circuit, and you measure circuit resistance hot to neutral on a circuit with no loads or shorts or faults, you're going to read a high-resistance short, not an open (which is what you'd see if there was a standard receptacle outlet in the circuit and not a GFI). It's 1.5 to 2 kOhm, IIRC. You're measuring the resistance of the injector coil.
Anyway, what's your source of information that a GFCI will trip if there's 1 mA leakage "in the ground"? And what exactly does that mean?
Cliff
Edited 3/1/2007 11:12 am ET by CAP
Anyway, what's your source of information that a GFCI will trip if there's 1 mA leakage "in the ground"? And what exactly does that mean?
It's essentially what you said - that current flow in the ground will trip the GFCI. The information is available on the internet, but my source was a GFCI designer at Eaton at a talk a few years back.
Oh, you mean in the grounding conductor.
I think that your info--that 1mA of current in the EGC will trip a GFCI--is wrong. It'd take at least 5 mA of current on the EGC (or, specifically, a sum of 6 mA +/- 1 mA on the EGC and any/all other ground fault paths) to trip a properly-functioning GFCI.
Cliff
"2. There is current flow in the ground greater than a threshold (typically 1 mA)"No, there is NO SENSE IN CURRENT IN THE EGC.Try it!There is not connection in the GFCI to the EGC.Here is a schematic for a GFCI using the LM1851. Notice the lack of an EGC.http://www.codecheck.com/gfci_principal.htm#1851What you are confused about is the feature that detects a grounded neutral.See http://www.codecheck.com/gfci_principal.htm#ngBut that not personal protection. It is to detect wiring mistakes.For personal protection it has to trip at 5 ma differenece in current between the hot and neutral, period.To test that we need to an unbalanced current hot and neutral.And the orginal situation was using a GFCI in a TWO WIRE CIRCUIT."To recap, one can make a GFCI tester that does not require a physical ground connection. It's still a 3 terminal device that satisfies Kirckhoff's laws, though - it's just that the third terminal is not a physical connection."Ok you claim to have a 3 terminal device. On terminal is connected to the HOT from the GFCI. A second terminal is connected to Neutral from the GFCI. There is nothing else to connect the 3 terminal to. Thus the current is zero.And the current in the first termainl equals that of the 2nd one and thus no fault..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Faraday's law for transformers:RMS voltage = 4.44 * frequency * number turns * area of core * flux in teslas.Flux at 3mm from 1-amp wire = 0.000006666666666666667 teslas (per the flux calculator). Note that flux is proportional to current and inversely proportional to distance.Note that the (area of core * flux in teslas) term is in essence capturing the total flux going through the turn of wire.In our case, the "turn" is presumably completed by the ground wire in the same cable as the "loose" wire. Assume that the distance between these is .06M and the flux is uniformly the above value. (In practice the flux would be would be smaller, and would vary considerably with position.)For a cable of 50 feet = 15.24 meters, the area of the "core" thus works out to 0.914 square meters. So the voltage induced in one wire by one amp flowing through the other wire is on the order of 4.44 * 60 * 1 * 0.914 * 0.000006667 = 0.00162 volt.To induce 50 volts, we'd have to scale up the current to about 30779 amps.If you complete the circuit with an external wire instead of the ground wire it doesn't change things much, since the vast majority of the flux is within a few mm of the wire carrying the inducing current.
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
I give up.
Y'all do what you want.SamT
Anyone who doesn't take truth seriously in small matters cannot be trusted in large ones either. [Einstein] Tks, BossHogg.
Faraday's law for transformers:
This isn't a transformer though - though you can make an assumption about the "turn" (as you did), you won't get an accurate answer.
That's why there is a different set of equations for the inductance between two parallel wires.
So, what are the equations for inductance between two parallel wires??
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
One other interesting thought.
We have been debating and speculating about why and how the bulb lights. But it appears that I am the only one who conducted a simple experiment to confirm my understanding and results. I find it's often useful to do a simple experiment as a "sanity check" on my theoretical results. Helps keep me from posting things that "make sense" but aren't correct in the real world - it's hard to argue with physical reality.
What experiment? I've seen a neon tester light on "dead" circuits while troubleshooting. What more do I need?
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
INDUCTIVE COUPLING (i.e. induced voltage
Induced, in this sense, does not mean Inductive. It is a catchall for inductive, capacitive, and radiant (EMF/radio waves).
In this particular situation we are discussing, there are so many factors involved that are incident specific that no one can make a general statement about whether or not the energy that causes the neon gas to flouresce is due to any one of the three most commonly thought of reassons; to wit, capacitive, inductive, or resistive.
The only reasonable answer is Induced Electromotive Force.
You are claiming that the typical capacitance of two parallel wires is on the order of 100 pF. I looked for a while and cannot find any reference to any number for that capacitance. You are also thinking that the calculated amperage, which is a one second average, and is the current that would flow in a shorted circuit, is equal to the instantaneous current flow in a voltage threshold switched circuit.
4.5uA for one second is equal to 450mA for 10uSec so one can not rule out capacitively induced EMF just because part of the equation doesn't fit.
By the same token, over the same time frames, one can not rule out induction as a factor because voltage applied at one end of long open circuit will push a current to the other end. Again this will be measured in ma - ua per second.
Try this experiment: Connect one end of a transformers' primary to 120VAC and leave the other end open. Then connect a good DVOM across the secondary winding.
A theory that only takes into account large scale effects will predict that since there is no current flow thru the open primary, the DVOM will read zero volts across the secondary, but that prediction will fail because a good DVOM is a sensitive instrument.
The more sensitive the measuring circuit one uses, the more one must take into account the cumulative effects of small reactances and conductances. A neon glow device is very sensitive to current flow over short time periods.
One says it tastes better and the other say it's less filling. Ya know what? They're both right as far as they go.SamT
Anyone who doesn't take truth seriously in small matters cannot be trusted in large ones either. [Einstein] Tks, BossHogg.
It lights my tester. I put a VOM is series and measured the voltage drop across the VOM. Then used the V/ohm spec to calculate actual current flow thru the VOM. The neon glow died somewhere between 50 and 30 uA.SamT
Anyone who doesn't take truth seriously in small matters cannot be trusted in large ones either. [Einstein] Tks, BossHogg.
Congratulations....you three have finally, utterly, totally, completely, positively, beyond a doubt, without question..............run me out of popcorn !!! LOLjust when ya think it's safe to scroll down the list to see what's new...now it's down to nano pico micro milli volts and micromilliamps.
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., wer ist jetzt der Idiot ?
I PMed Orvillefor ya, he should be there soon with more Pcorn.SamT
Anyone who doesn't take truth seriously in small matters cannot be trusted in large ones either. [Einstein] Tks, BossHogg.
Thanks, If he shows up,
it would be a miracle.!He WAS a big deal over to Valparaiso.
the town even had a Popcorn Festival in the late 70s and his popcorn plant was right on US 30 East of town just past the airport.
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., wer ist jetzt der Idiot ?
300ua was the rated current. It will light dimly on much less.
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
So how am I grounded when standing on a wooden or fiberglass ladder? I use this neon light test when working on knob & tube wiring where no color exists to determine neutral. It is capacitive coupling.And yes, I have had the neon light glow when attached to a non connected wire. Again, capacitive coupling.Of course now I just use the non contact voltage testers!Frank DuVal You can never make something foolproof because fools are so ingenious.
So how am I grounded when standing on a wooden or fiberglass ladder? I use this neon light test when working on knob & tube wiring where no color exists to determine neutral. It is capacitive coupling.
Hi, Frank. Thanks for your comments.
Maybe it's just confusion in terminology. What I mean is that there is an AC impedance to ground through the body. Considering that a capacitor is a frequency dependent impedance, what I am saying could be described as a capacitive impedance.
I think of the term "capacitive coupling" in the electronic usage - for example, the coupling between a printed circuit board trace and the ground plane, due to the dielectric of the circuit board material. I had that perspective in my mind, which perhaps narrowed my thinking a bit too much.
Keep in mind, though, that there are no perfect insulators (or conductors, for that matter). Your fiberglass ladder is a conductor, just a very poor one. Copper wire is a much, much better conductor.
When talking about AC systems and earth grounds, one is generally referring to an AC ground path, not a DC ground path. Measuring the impedance to earth ground on an AC system is not a trivial matter. There are special testers that do that, but it's not practical to measure with common test equipment.
I had a similar thing happen years ago in a splice between two aluminum wires leading into the home from the pole. Once the wire was respliced and connected it was fine. The difference in voltage reading was due to the slight amount of invisible corrosion on the surface of the strands of the aluminum wire creating an insulation layer around the aluminum itself. So it created an layer of insulation around the aluminum metal that allowed some current and voltage to pass but not all. It made the connection resistant to current flow. I found it by checking the resistance of the wire and found it to be too high. Eventually I was able to locate the splice.
Maybe this is helps. It's pretty clear to me. http://www.coleparmer.com/techinfo/techinfo.asp?htmlfile=Fluke-volt-affects.htm&ID=292
Maybe you should get a "wiggy" (solenoid tester) for voltage testing. Saves a lot of confusion.
http://www.lowes.com/lowes/lkn?action=productDetail&productId=67600-296-VT-1&lpage=none
http://www.lowes.com/lowes/lkn?action=productDetail&productId=87134-1781-GVT-92&lpage=none
I think I finally understand. I think what is being said is that becaues there is a nearby circuit that is likely energized, and I'm testing a circuit with an open ground, that the electromagnetic field of the wire nearby is close enough to show measurable voltage present in the adjacent dead wire, in this case the open ground.
From the link they're suggesting that spare wires run, but not used, in conduit for example, when measured may show ghost voltage even though they are completely dead, because of adjacent wires in the conduit are energized. Because the wires are close together and running side by side it creates a capacitive voltage similar to a capacitor that stores voltage. In my case, my open ground wire acts like one of those spare wires in conduit, it's not being used as it's open, unconnected and therefore is showing some voltage present, confusing as the link suggests happens, the person doing the testing. And they said it could show as much as 50% of the voltage. Well I read 71%, a little more than 50% but close enough. If at first you don't succeed, try using a hammer next time...everything needs some extra persuasion from time to time. -ME
I think you got it now. Still think you should get a solenoid tester. They don't get fooled because it takes some power to make them read anything. Meters can read voltage without taking much power at all, so they are sometimes reading a static voltage rather than a live circuit.
As an engineered I did evaluate all posibilities.
99% likely that the ground was opend.
0.00000000000000001% that the AC control line was shorted.
0.99999999999999999% that is was something else.
"If you say so, but that's not the way an engineer would approach the problem. To an engineer, that conclusion is not obvious, though one possibility. An engineer would consider the range of possibilities, evaluate which are most likely, and then test for each of them, starting with the most probable."
Exactly. That is why, as an engineer, I told him verify where the ground wire was connect. And he found that it wasn't.
I did not suggest that he started looking at the AC control lines like "some people suggested".
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
As an engineered I did evaluate all posibilities.
99% likely that the ground was opend.
It's pointless to argue about it, but I am a degreed engineer, and I can't imagine any experienced engineer would leap to presumptions like that.
Edited 2/16/2007 9:05 am ET by woodturner9
It's pointless to argue about it, but I am a degreed engineer, and I can't imagine any experienced engineer would leap to presumptions like that.
It's not a presumption, it's experience. And you are demonstrating a lack of experience in shoddy home wiring.
What we have here is a center tapped transformer and 3 insulated wires in an insulating armor sheath, 2 of which are expected to be connected to the center tap, which is also bonded to earth,the third to be on one end leg. Granted, the "Ground" conductor be a bare wire.
Your presumption was that one of the doubly insulated, grounded center tap wires had shorted to a fourth insulated wire from a different, low voltage, floating transformer, and somehow, not being shunted to earth, the voltage from that fourth wire was getting to the meter, opposing the voltage on the "Hot" leg of the main transformer.
Your presumption requires two seperate problems acting in concert. 1; the ECG is shorted to a low voltage tranformer, and 2; the green wire (ECG) is not connected to ground.
Oh! That's what Bill said.
SamT
Anyone who doesn't take truth seriously in small matters cannot be trusted in large ones either. [Einstein] Tks, BossHogg.
Edited 2/15/2007 8:51 am by SamT
s not a presumption, it's experience. And you are demonstrating a lack of experience in shoddy home wiring.
Trust me, I have dealt with WAY too much shoddy wiring over the last 30 years.
Your presumption requires two seperate problems acting in concert. 1; the ECG is shorted to a low voltage tranformer, and 2; the green wire (ECG) is not connected to ground.
No, only your first statement is required - ground is a separate issue
I think I see the confusion, though - you are assuming a center tapped transformer and a different configuration that I had in mind.
Edited 2/15/2007 11:34 am ET by woodturner9
Edited 2/16/2007 9:12 am ET by woodturner9
WhateverSamT
Anyone who doesn't take truth seriously in small matters cannot be trusted in large ones either. [Einstein] Tks, BossHogg.
""and I can't imagine any experienced engineer would leap to presumptions like that.and I can't imagine any experienced engineer would leap to presumptions like that."So if a light goes out and the other lights in the house are still on you don't "jump to conclusion" and replace the bulb.Rather you check the breaker, check the switch, see if the socket in the fixture, and last - but not least - check to see if the AC control wiring is shorted to duct work, and only after checking all of those you replace the light bulb?And it was not a LEAP. It was the deduction that I made based on many years of education, years of engineerign practice including a lot of trouble shooting, and my practical experience with house wiring.I am sorry if you are not able to take the symptoms and not able to make a logic deduction of the problem."If you are an engineer, in what state are you licensed?"I am not licensed as an PE because I never did any work that required licensing.I have a BEE, which is a 5 year probram. So intensive that they later offered MS degrees based on that course work along with paper work showing that had a performed work as an engineer.By that time I already had an MS and was finish course work on a PhD so I never bothered to get it."A-holes. Hey every group has to have one. And I have been elected to be the one."Only after having to deal with certain people..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Edited 2/15/2007 7:10 pm by BillHartmann
I really liked his bit about how even if the EGC was earthed, when the AC control wire shorted to it, the AC control voltage would show up on the fixture end of the EGC.
Hmnn, 42 hunh?SamT
Anyone who doesn't take truth seriously in small matters cannot be trusted in large ones either. [Einstein] Tks, BossHogg.
So if a light goes out and the other lights in the house are still on you don't "jump to conclusion" and replace the bulb.
Of course not - and that is not at all what I said. Maybe you didn't get my point, or maybe I did not make my point clearly enough?
"A-holes. Hey every group has to have one. And I have been elected to be the one."
Only after having to deal with certain people.
Wow - we agree on yet something else :-)
I am not licensed as an PE because I never did any work that required licensing.
FWIW, in the US, one must be licensed to legally refer to oneself as an engineer. The sole exception is the "industrial exemption", where a company that manufactures a product can title their employees engineers, but they still can't do "engineering work", as that phrase is defined in the law.
I'm here to share my knowledge and experience to help others, and I assume you are too. I presume most of us are here for that reason. Maybe if we tried to help each other more rather than looking for nits to pick in each others' posts, we would do better at achieving this goal.
Thanks.
Edited 2/16/2007 8:50 am ET by woodturner9
FWIW, in the US, one must be licensed to legally refer to oneself as an engineer. The sole exception is the "industrial exemption", where a company that manufactures a product can title their employees engineers, but they still can't do "engineering work", as that phrase is defined in the law.
What year did that go into effect?
FWIW, in the US, one must be licensed to legally refer to oneself as an engineer. The sole exception is the "industrial exemption", where a company that manufactures a product can title their employees engineers, but they still can't do "engineering work", as that phrase is defined in the law.
What year did that go into effect?
For what state? It's not a new requirement - it has been the law in the US for at least 50 years. There are exceptions - they don't recognize the industrial exemption for engineers in Maine, for example - but the basic requirements are nationwide.
If you go to the website for your local licensing board, they will usually have a page listing recent disciplinary actions. If your state is like most, there will be many pages of "practicing engineering without a license".
Please note, though, that "practicing engineering" has a specific definition. Much of what people colloquially refer to as "engineering" is not engineering at all. And though it is technically illegal to call someone a "sanitation engineer" or something like that, in practice the boards are so swamped that they try to focus on the complaints and the cases where there is more likelihood of public harm.
It's not a new requirement - it has been the law in the US for at least 50 years.
I got my BSME in 1992 in California. In my final semester there, I took a required course in "Engineering Ethics" that covered many different non-technical aspects of engineering. Anyway, the professor (and I believe the text, as well) specifically covered the use of the term "engineer", and we discussed whether it would be advantageous for engineers to legally regulate the use of the term "engineer" in much the same manner as doctors or lawyers do.
Anyway, it was my recollection that no such law existed in California at that point in time. Although it was irksome to hear people try to puff up their titles (janitor = sanitation engineer, housewife = domestic engineer), there didn't seem to be any legal recourse.
What I remembered was a distinction between "engineer" and PE (professional engineer). Where I now live, there is a multi-step process by which an individual obtains a license from the state in order to call himself a PE (complete with fancy rubber stamp and license number). Maybe this is the same thing you're talking about in terms of "practicing engineer" -- I just may not be all that familiar with the language.
FWIW, in the US, one must be licensed to legally refer to oneself as an engineer.
It's not a new requirement - it has been the law in the US for at least 50 years.
I think you're shooting from the hip there, pardner.
I think if someone claimed to be a registered professional engineer, but was not, AND he or she approved (stamped) calculations, designs, or specifications that by law had to be so stamped, then I think there'd be a violation of some law.
But to have to be licensed to even use the title "engineer"? And you imply it's a requirement throughout the US. Can you cite any federal law or a the laws of a few large states that prohibit the use of the title "engineer" except be a licensed engineer?
Cliff
But to have to be licensed to even use the title "engineer"? And you imply it's a requirement throughout the US. Can you cite any federal law or a the laws of a few large states that prohibit the use of the title "engineer" except be a licensed engineer?
Sure. Since your profile says you are in California, I'll provide the California links, but it's similar throughout the US, though California is on the more liberal/lax end of the spectrum.
http://www.dca.ca.gov/pels/pe_act.pdf
6702.1 "Electrical Engineer".. means a professional engineer... and refers to one who practices or offers to practice electrical engineering in any of its phases."
(similar sections for other branches of engineering)
6704 "...no person shall practice civil, electrical, or mechanical engineering unless appropriately licensed or specifically exempted from licensure under this chaper, and only persons licensed under this chapter shall be entitled to take and use the titles "consulting engineerg", "professional engineer", or "registered engineer", or any combination of those titles or abbreviations thereof"
It appears from that document that California has deleted the industrial exemption, which is surprising - many view CA as being relatively liberal in their requirements. There is a growing movement to eliminate the industrial exemption, though, and it's likely that all states will adopt it within 10 years or so. When that happens, no person would be permitted to do engineering work without being licensed. That would include work currently done by people with engineerin degrees but no license.
There is no place those regs that say that you have to be licensed to use the title engineer.You need to read the whole thing rather than cherry picking."6747. Exemption for industries
(a) This chapter, except for those provisions that apply to civil engineers and civil
engineering, shall not apply to the performance of engineering work by a manufacturing, mining,
public utility, research and development, or other industrial corporation, or by employees of that
corporation, provided that work is in connection with, or incidental to, the products, systems, or
services of that corporation or its affiliates.
(b) For purposes of this section, ôemployeesö also includes consultants, temporary
employees, contract employees, and those persons hired pursuant to third-party contracts.""6731.5. Electrical engineering defined
(a) Electrical engineering is that branch of professional engineering described in Section
6734.1 that embraces studies or activities relating to the generation, transmission, and utilization
of electrical energy, including the design of electrical, electronic, and magnetic circuits, and the
technical control of their operation and of the design of electrical gear. It is concerned with the
research, organizational, and economic aspects of the above.
(b) The design of electronic and magnetic circuits is not exclusive to the practice of
electrical engineering, as defined in subdivision (a).""6737.3. Exemption of contractors
A contractor, licensed under Chapter 9 (commencing with Section 7000) of Division 3, is
exempt from the provisions of this chapter relating to the practice of electrical or mechanical
engineering so long as the services he or she holds himself or herself out as able to perform or
does perform, which services are subject to the provisions of this chapter, are performed by, or
under the responsible charge of a registered electrical or mechanical engineer insofar as the
electrical or mechanical engineer practices the branch of engineering for which he or she is
registered.
This section shall not prohibit a licensed contractor, while engaged in the business of
contracting for the installation of electrical or mechanical systems or facilities, from designing
those systems or facilities in accordance with applicable construction codes and standards for
work to be performed and supervised by that contractor within the classification for which his or
her license is issued, or from preparing electrical or mechanical shop or field drawings for work
which he or she has contracted to perform. Nothing in this section is intended to imply that a
licensed contractor may design work which is to be installed by another person.".
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Edited 2/18/2007 12:06 pm by BillHartmann
There is no place those regs that say that you have to be licensed to use the title engineer.
Actually, it does, though it may require an attorney's interpretation to make that clear.
In any event, in all states in the US, the title "engineer" can be legally used ONLY by a licensed P.E., with the exception of the "industrial exemption" that is valid in only certain states.
If you aren't convinced, I suggest you call your state's licensing board and ask them. I would not advise giving your name, though, because that would likely get you added to the list for prosecution.
Edited 2/19/2007 8:24 am ET by woodturner9
"only persons licensed under this chapter shall be entitled to take and use the titles "consulting engineerg", "professional engineer", or "registered engineer", or any combination of those titles or abbreviations thereof""PROFESSION ENGINEER, CONSULTING ENGINEER, REGISTERED ENGINEER.I never said that I was any of those..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
I take it this enlightening....(yawn)....bickering about who's an engineer and who ain't is due to Engineer's Week, Feb 18-24!!??http://www.eweek.org/
"only persons licensed under this chapter shall be entitled to take and use the titles "consulting engineerg", "professional engineer", or "registered engineer", or any combination of those titles or abbreviations thereof""
PROFESSION ENGINEER, CONSULTING ENGINEER, REGISTERED ENGINEER.
I never said that I was any of those.
Sorry, I though you had said you were an "engineer", which is an abbreviation of "professional engineer".
Woodturner, now I have to correct you! You said: "Sorry, I though you had said you were an "engineer", which is an abbreviation of "professional engineer".I held several ENGINEER titled jobs before I became a Professional Engineer. Engineer is not an abbreviation for Professional Engineer. Engineer could mean anybody that studied engineering. It is when you add the extra adjective that licensing becomes necessary. Very few engineering graduates get licensed as Professional Engineers. The license is not necessary for 90% of engineering work. CHeck the want ads in your area for engineers and see how many ads require PE licenses for the job.
Frank DuVal You can never make something foolproof because fools are so ingenious.
Back in the late 60's or early 70's WI tried to get Byrcuses Engineering because they used the name engineer and they wheren't a professional engineering company. BTW, they are the ones that make the huge draglines and power shovels for mine.I tried to verify that from Byrcuses history. But the corp was Byrcuses-Erie until 1997. So it was either a division or a I am not remembering the right company.I know that the time that everyone thought that it was a big joke because no one would be comfused that Burcuses was holding themselves out to be professional engineers to the public..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
I was told about 30 years ago that Texas had a law that effectively prohibited the use of the title "engineer" as an employee rank (no "industrial exemption"). But more recently I know companies have been using "engineer" there.
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin