Possiable Ground Problem - Mystery to me - Amp on ground

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Old 09-23-08, 12:34 PM
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Possiable Ground Problem - Mystery to me - Amp on ground

HI;

I have run into something that I am quite confused about. The folks on one of the other DIY sites did make some comments about my question, but didn't end up telling me anything that allowed me to narrow down the problem and understand what is going on. I came across this site, and saw several people here that look like they might have a better grasp of what I have going on.

I have a 100A panel, from the 1960's, Pushmatic. It is grounded via a #6 to the water pipe. When my panel is completely off at the main, and I put a clamp meter on the grounding wire that is bonded to the water pipe, I read about .6amps. - It has been suggested this is stray voltage, however I get the readings consistantly.

Then when my panel is hot, I see even more amperage going out the ground, 2, or even 3 full amps or more, depending on the load on my panel. If I plug in a resistance appliance and turn it on, the load on my ground wire increases by another amp or more.

How could that all be caused by stray? There is no meaningful amount of voltage I have been able to measure on the ground wire (read 1.8v one time), but I keep seeing the amperage.

All my connections are tight with wire that is in good condition.

I am concerned that there is power making it back to ground from outside my home that is energizing my water pipe. However if that was the problem, then why would I see the increase in amperage when I run a load on my panel?

Thank you very much for any help or suggesting you can provide. I can perform and necessary checks or testing myself if there is anything you would like me to look at.

Jamie
Wisconsin
 
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Old 09-23-08, 12:52 PM
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Your readings are probably correct, and can be normal.

It is standard procedure to use the copper water pipe as a grounding electrode for your electrical service. Your neighbors' houses have this connection also, and the pipes are connected to the same municipal water system. This creates an electrically conductive path between all of the homes in the neighborhood which does allow some neutral current to flow through the service ground and neutral wires even when the main breaker is off.

A common myth is that "electricity takes the path of least resistance" when in fact electricity takes all available paths inversely proportional to the resistance of each path. (I suppose that doesn't flow off the tongue as easily) So, when presented with the path out the neutral conductor and the path through the ground wire to the water pipe to the neighbor's house to his neutral wire, the electricity will take both paths. However, only a small amount takes the longer high resistance path.

If all connections are tight, and you are not experiencing any symptoms to indicate a bad neutral connection (dimming/brightening lights, appliance malfunction, partial loss of power) then I do not see any trouble with your observations.
 
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Old 09-23-08, 03:23 PM
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Hello Jamie


Ben is absolutely correct in his description. And you are not reading stray voltage....

When investigating currents on ground wires you should take three readings. One on the metal water pipe where it enters the home. One on the water pipe bond wire (as you have done). And finally one on the water pipe immediately after the water pipe bonding clamp. Reasoning is that all currents either coming or going will be present on the pipe where it leaves the house. Any currents entering your home on the water pipe may split at the bonding clamp point as two paths may exist at that point. If current splits at the bonding clamp some goes to the bonding wire (#6 in your case) and some goes on to the other water pipes in your home then you will not get a accurate reading of the net current entering or leaving your home. You need to determine if current is following one path or two. Ground rods come into play but lets leave that out.

So for example I take a reading on the water pipe at the entrance to the home and get 1.4 amps. Lets call that point A. I take a reading at the bond clamp and bonding wire and get
.8 amps.. point B... and finally a reading on the water pipe right after the bonding clamp and get .6 amps... point C. So I know current is finding a path to the neutral of the service transformer by splitting at the bonding point of the water pipe to the homes main panel. What I don't know is if it is leaving or coming. These currents are normal currents.
It is also normal for these currents to increase or decrease depending on what 120 volt appliances are operating. So lets say I turn on a 60 watt light bulb and take a reading at point A and I get 1.75 amps. This tells me that the light bulb neutral current is leaking to the water pipe at .35 amps of its .5 amp total due to its wattage. This also tells me it is in the same direction as the initial current of 1.4 amps because I have an addition of the current or increase. Meaning that the light bulb is on the same leg of the service as the initial current. If in the opposite direction or opposite leg (you have two legs remember) there would be a decrease of current by .35 amps. Opposite legs.. neutral current cancels...same leg neutral current adds.
So the point of this.... it is not abnormal for current to be present on the water pipes and these currents will increase or decrease considerably depending on what neutral load is applied to the dwelling service neutral and what the wattage of the appliance is and service leg in the panel that the appliances are are operating from. There is very little to insignificant voltage involved in neutral current on water pipes.

Though these currents are objectionable they cannot always be eliminated. Incoming water pipe currents can be prevented if you install a section of non-conductive pipe in the main line entering the house. As for code compliance in doing that you would need to install it somewhere after the pipe is past the 10 foot point when leaving the home.

3 amps showing on the water pipe would not be surprising as a net current if you ran a toaster or other high wattage 120 volt appliance.

Further test can be done at the service neutral to determine if current is leaving or coming into your homes electrical system.
 

Last edited by Bruto; 09-23-08 at 05:15 PM.
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Old 09-23-08, 10:17 PM
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HI;
Thanks so much for responding, I am so relived to hear that someone understand what I am talking about. I will respond below:
When investigating currents on ground wires you should take three readings. One on the metal water pipe where it enters the home.
Just did some more tests, Tonight I read .60 just where the pipe enter the home on the floor.
One on the water pipe bond wire (as you have done).
I did this test again tonight, and I saw .60 the same reading as I got below the clamp on the pipe.
And finally one on the water pipe immediately after the water pipe bonding clamp.
This test being done after the clamp (on pipe that is futher into my home) I read about .06 or about 1/10th of what I read directly below this spot.
I add resistance (turn on a heat gun that draws about 15A) and both of the .6 numbers jump to 1.6
following one path or two. Ground rods come into play but lets leave that out.
There are currently no grounding rods installed here, I presume it was not a requirment in 1963.
I have seen low amp readings on the houses water pipes at other locations in the basement, but tonight was not able to see anything. However the gas pipe read about .06 tonight.
service as the initial current. If in the opposite direction or opposite leg (you have two legs remember) there would be a decrease of current by .35 amps. Opposite legs.. neutral current cancels...same leg neutral current adds.
So your saying that I would see the current when I draw from one leg but not from the other?
So the point of this.... it is not abnormal for current to be present on the water pipes and these currents will increase or decrease considerably depending on what neutral load is applied to the dwelling service neutral...
Now, maybe this is a terriably stupid question, but does this voltage that is being sent back to ground get metered? I mean, do I pay for those amps that I am seeing going to the earth?
Is the way to avoid this by having a perfectly balanced planel? (Is this part of the reason why 240V appliances are more efficent, as they draw equal loads on both sides of the panel at the same time and nothing is wasted?)
If my panel was drawing a perfectly balanced load, would I see little to no loss to ground? i.e. if I ran a 240 ac as my old load, would I see almost no loss?
Though these currents are objectionable they cannot always be eliminated. Incoming water pipe currents can be prevented if you install a section of non-conductive pipe in the main line entering the house. As for code compliance in doing that you would need to install it somewhere after the pipe is past the 10 foot point when leaving the home.
As long as they are not dangerous or harming anyone, then it doesn't really bother me. Until now, no one has been able to tell me if this was normal or not. I know there is confusion over the what the NEC says about grounding and many people belive the NEC to read that the only time there will be power on a ground is in the event of a fault, however I think this is incorrect as I am finding out here.
3 amps showing on the water pipe would not be surprising as a net current if you ran a toaster or other high wattage 120 volt appliance. Yep, running the heat gun as a test, draws as much as a toaster would.
Further test can be done at the service neutral to determine if current is leaving or coming into your homes electrical system.
Would this be testing I could do, or testing the power co would need to do? i.e. when you say service netural are you speak of on the pole transformer or just the neutral in my panel?
I am very curious now if the amps I am seeing that are likely leaving the house when I run an unblanced load are being metered and I am paying for them. I had a electrician try to explain to me that something like this happens when your load is unbalanced and that you could basically run 2 120V AC units for the cost of 1 if they each ran at the same time each on one side of the panel. I asked a number of people about this and they all told me the guy was crazy. However the guy was an electrical engineer and had been liceansed as a master electrican in like 9 states... So I still have never quite figured out if he was correct and this is what he was talking about or what...
Thanks so much. I am happy to do more testing at the panel if you can let me know what you would like done.
Jamie
 
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Old 09-23-08, 10:22 PM
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A common myth is that "electricity takes the path of least resistance" when in fact electricity takes all available paths inversely proportional to the resistance of each path. (I suppose that doesn't flow off the tongue as easily) So, when presented with the path out the neutral conductor and the path through the ground wire to the water pipe to the neighbor's house to his neutral wire, the electricity will take both paths. However, only a small amount takes the longer high resistance path.
Yes, I have heard this before, and I think i see this happening as I see a bit of amperage on my Gas line as well, but it is proboly the path with the most resistance, so just a tiny bit flows in or out on the gas pipe.
If all connections are tight, and you are not experiencing any symptoms to indicate a bad neutral connection (dimming/brightening lights, appliance malfunction, partial loss of power) then I do not see any trouble with your observations.
Well none of the text book symptoms per say, but I do see lights flicker a bit more than I think they should, particually when we get a motor startup, like on the fridge. Or when using a laser printer on the fax machine, the incandescent light bulb in that room flashes for quite a while.
However, nothing were it dims or brightens. Just that momentary flicker
Thank You,.
Jamie
 
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Old 09-24-08, 09:18 AM
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Your tests appear to be perfectly normal due to the grounding design of our electrical utility systems.

So your saying that I would see the current when I draw from one leg but not from the other?
The .6 amps you are seeing is the existing current on the water pipe. It is either the total neutral current produced by the loads connected to one hot wire of the service or the net (unbalanced load) of neutral current from both legs and their loads....ie...leg A is 4 amps leg B is 10 amps....10-4 = 6 amps showing on the service neutral or possibly the water pipes. It may also be current from some other source. It takes some investigation by a experienced electrician to determine this in some cases.

T
Now, maybe this is a terriably stupid question, but does this voltage that is being sent back to ground get metered? I mean, do I pay for those amps that I am seeing going to the earth?
Questions aren't stupid just a way to learn....

No voltage gets metered only amps. The amps your seeing are not metered. Your are not paying for these amps.

Is the way to avoid this by having a perfectly balanced planel? (Is this part of the reason why 240V appliances are more efficent, as they draw equal loads on both sides of the panel at the same time and nothing is wasted?)
No it costs the same (if thats what your asking) to run either 120 volt devices or 240 volt devices ...amps are amps you can't change that. 240 volt loads operate at 1/2 the amperage of 120 volt loads so plug this into ohms power law (Watts = volts x amps) and do the math....it comes out the same... You save money on installation costs as the wire can be smaller with 240 volt loads.

If my panel was drawing a perfectly balanced load, would I see little to no loss to ground? i.e. if I ran a 240 ac as my old load, would I see almost no loss
There is no neutral current for 240 volt loads to lose the only "losses" are due to heat losses in the wires due to load plus wire resistances.

As long as they are not dangerous or harming anyone, then it doesn't really bother me. Until now, no one has been able to tell me if this was normal or not. I know there is confusion over the what the NEC says about grounding and many people belive the NEC to read that the only time there will be power on a ground is in the event of a fault, however I think this is incorrect as I am finding out here
Yep..thats correct. What you are seeing is perfectly normal. But it never hurts to understand why or to make sure that you do not have anything unusual or failing in your electrical system like a lose service neutral or corroded service neutral causing high resistance and forcing more current on to your water pipes than should be. The question is determining whether or not your current would be classified as objectionable...ie...preventable. In most cases current on water pipes 3 amps or below is quite normal but it's a matter of determining if you can decrease that current by making sure you do not have any issues going on that you can correct. My opinion is you likely have nothing to worry about. A professional will take a gauss reading in different places in your house to detemine if you have amperage on your water pipes that is creating high magnetic fields. 3 amps will create a pretty good magnetic field. Whether it is harmful or not is up to debate.

Would this be testing I could do, or testing the power co would need to do? i.e. when you say service netural are you speak of on the pole transformer or just the neutral in my panel?
Fooling with possible dangerous water pipe currents should be left to a professional. If you turn your main breaker off and current still shows on the water pipe its source is external in most cases. But you will nearly always have current on the water pipes due to the nature of the grounding in our electrical systems. And yes I'm speaking of the neutral from your panel to the center tap of the transformer.

Your not paying for any of this amperage your measuring....

The master electricians theory is interesting but wrong, I doubt he is crazy though....
 
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Old 09-24-08, 10:48 AM
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It sounds like everything is well within expected tolerances in your home.

Originally Posted by jamied View Post
I had a electrician try to explain to me that something like this happens when your load is unbalanced and that you could basically run 2 120V AC units for the cost of 1 if they each ran at the same time each on one side of the panel.
You could theoretically run two 120V units for the same cost as one 240V unit...

Metering is pretty exact. For the power company, meters are the cash register. They make certain everything is counted properly by using robust meter technology and data analysis of typical vs. abnormal usage. Those who try to tamper with the meter are either caught when the meter reader notices broken seals or electrocuted while attempting a bypass.

The meter actually measures total energy used in kWh (kilowatt-hours). This measurement is independent of voltage or current (amps), so balancing the panel, swapping 120V units for 240V units, high voltage, low voltage, etc does not fool the meter.
 
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Old 09-24-08, 02:17 PM
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No voltage gets metered only amps. The amps your seeing are not metered. Your are not paying for these amps.

How does the meter know the difference between power that I consume, and power that goes back to ground via the water pipe or other? I understand how it could calculate proper readings if everything unused was returning on the neutral, but since it is not all returning on the neutral, then I don't understand how the meter know the difference between 4 amps that is feeding into the ground via the water pipe and 3 amps that my lamp post uses up. I belive what your saying about the meter not charging me, I just don't understand how it does it. I must be missing something.
classified as objectionable...ie...preventable. In most cases current on water pipes 3 amps or below is quite normal but it's a matter of determining if you can decrease that current by making sure you do not have any issues going on that you can correct. My opinion is you likely have nothing to worry about. A professional will take
All the connection seem to be nice and tight. I am going to replace the panel in the future, it's on my to do list. I am planing to put in a new QO 40 or 42 position load cetner. I will then ofcourse know with absolute certinty that the wires are all tight.
a gauss reading in different places in your house to detemine if you have amperage on your water pipes that is creating high magnetic fields. 3 amps will create a pretty good magnetic field. Whether it is harmful or not is up to debate.
What kind of harm are we talking about? Wiping out hard drives on computers? Would this EM Field possiably cause the lights to flicker more than they otherwise would when I run a motor?
Fooling with possible dangerous water pipe currents should be left to a professional. If you turn your main breaker off and current still shows on the water pipe its source is external in most cases. But
Yes, I do still have amps there, but it is low, around .6 amps. -- SO it sounds like I am not dealing with anything on the water pipes that would be considered dangerous right?
Is there any shock danger to adding in some grounding rods, and bonding them to the panel? When I install some rods, should I treat them as hot when I bond them to the panel, just incase something is amis? I just don't want to end up with power flowing through me to ground. I have no problem treating the grounding rods as being hot, (I treat just about everything as hot unless it is new wireing that isn't hooked up, then you know your not going to have a problem). I just am curious if it is a potential problem.
you will nearly always have current on the water pipes due to the nature of the grounding in our electrical systems. And yes I'm speaking of the neutral from your panel to the center tap of the transformer.
How do you meter what is return on your neutral if your neutral wire isn't physically accessiable in your panel? My netural is tucked behind my neutral bar, and is not accessable via a clamp meter.
Thanks again
Jamie
 
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Old 09-24-08, 02:30 PM
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Metering is pretty exact. For the power company, meters are the cash register. They make certain everything is counted properly by using robust meter technology and data analysis of typical vs. abnormal usage. Those who try to tamper with the meter are either caught when the meter reader notices broken seals or electrocuted while attempting a bypass.
Ofcourse I am not talking about any way to cheat the power company or doing anything illegal, I am just wanting to understand waste / and possiably more efficent ways to do things.
The meter actually measures total energy used in kWh (kilowatt-hours). This measurement is independent of voltage or current (amps), so balancing the panel, swapping 120V units for 240V units, high voltage, low voltage, etc does not fool the meter.
My thought was not of fooling the meter, but an increase in efficency via a reduction in waste. I was assuming that the amperage that I see going to the ground (or returning via neutral) is waste due to inefficency, and I don't quite understand how the meter knows not to charge me for that. (I can understand how it would know not to charge me on power that is returned via service netural, but when power is dumped out via the ground, how would the meter know what that power was used for?)
Thanks again
Jamie
 
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Old 09-24-08, 02:54 PM
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I understand that you aren't interesting in cheating the meter. I was just pointing that out as an example of why the power company has already thought of everything. :-)

The meter does not monitor the neutral wire at all, only the hots. Once the power has flowed into the home via the hot wires, the meter will never see it again so it doesn't really matter (from a cost perspective) whether it flows back on the neutral wire or on the water pipe. Likewise for any of your neighbors' power flowing back through your neutral. You can examine this directly by switching off the main breaker and watching that the dial on the meter will stop, even though your amp meter shows current on the neutral and/or water pipe.
 
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Old 09-24-08, 03:04 PM
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Originally Posted by jamied View Post
What kind of harm are we talking about? Wiping out hard drives on computers? Would this EM Field possiably cause the lights to flicker more than they otherwise would when I run a motor?
It is in the same realm as various other "toxins", cell phone radiation, living under power lines and similar stuff that is in our daily environment which some people believe may be detrimental to health, but there has been little or conflicting scientific and medical evidence to substantiate it. (please no one start a flame war on these topics -- they are examples only)

It shouldn't have anything to do with flickering lights, which is normal in small doses.

it sounds like I am not dealing with anything on the water pipes that would be considered dangerous right?
I agree. Normal and not a problem.

Is there any shock danger to adding in some grounding rods, and bonding them to the panel?
No danger. Rods should be driven flush to the ground, bonded with an acorn clamp, and #4 or #6 copper wire to the panel.

How do you meter what is return on your neutral if your neutral wire isn't physically accessiable in your panel?
It's not always easy to do safely in cramped panels. Sometimes the only way would be for a professional to use live gloves and reach in there.
 
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Old 09-27-08, 10:57 AM
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to start off you have to understand that at the telephone pole the secondary side of the transformer is 240v potential with a neutral that is the centertap but that centertap also has a ground wire on it that goes directly to earth via a ground rod. all the houses on the street are fed through this system and there are transformers all connected to the same line in parallel keeping voltage constant and the amperage up. i do not know how long in between the distance is from transformer to transformer but. maybe your answer lies with there maybe a house that is in between transformers has a better path going through the ground and up your neutral back to the transformer that is one way. another, do you have a house that is in back of yours that the wires from the pole travel right by your house to get to? it might find travelling through the ground to your house is a better path than its neutral or ground wire even. maybe it could also be the condition of your soil in the area are they rich with minerals or not i do not believe it is something to concern you if all is well and working in your house i just merely wanted to give you something to maybe satisfy your couriosity.
 
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