How much amperage is considered "normal" on a GEC?

[ivsenroute]

Not so funny question. On a 600A service that fed 8 apartments and a house panel, is any current on the GEC outside the building considered normal? Would 1.2A be a concern?

In a perfect world you would expect all of the imbalance current to return on the neutral but since the neutral and GEC is tied together at the service, shouldn't we expect some current to return on the GEC?

I can't afford a ticket to Perfect World but there has to be some of this imbalanced current that is expected.

Thoughts?

 

[Isaiah]

Not so funny question. On a 600A service that fed 8 apartments and a house panel, is any current on the GEC outside the building considered normal? Would 1.2A be a concern?

In a perfect world you would expect all of the imbalance current to return on the neutral but since the neutral and GEC is tied together at the service, shouldn't we expect some current to return on the GEC?

I can't afford a ticket to Perfect World but there has to be some of this imbalanced current that is expected.

Thoughts?

There will normally be a small amount of current on the GEC. The vast majority of current will travel on the grounded conductor back to the transformer XO which has a much lower resistance than the GEC to earth connection.


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[ptonsparky]

Not so funny question. On a 600A service that fed 8 apartments and a house panel, is any current on the GEC outside the building considered normal? Would 1.2A be a concern?

In a perfect world you would expect all of the imbalance current to return on the neutral but since the neutral and GEC is tied together at the service, shouldn't we expect some current to return on the GEC?

I can't afford a ticket to Perfect World but there has to be some of this imbalanced current that is expected.

Thoughts?

I would expect some and would hazard a guess that 1.2 amp would not be of concern. Did you happen to measure the neutral current?

I just went went to the basement and clamped the #4 to my rebar and hit the mitre saw. Largest 120v load in my house. Nothing, but then it’s a full-size neutral. 200 amp service.

Apples to oranges comparison, but you had me wondering.

 

[Buck Parrish]

Yep . A little bit is normal. Some call it objectionable current …

https://www.youtube.com/watch?v=5TWRikH5hfU

 

[infinity]

A few amps is normal especially if you're connected to a city water system where neutral current can flow on the water pipe between houses.

 

[winnie]

Generally not a concern if you are an electrician and are not seeing any problems.

But it is a concern if you are a plumber. As mentioned above, common water piping between buildings can form a low resistance parallel path for neutral current. In some cases plumbers have experienced electric shock when cutting water pipes used as ground electrodes.

Another situation where this level of current would be a concern is if you had a customer complaining of shocks from water piping...but this might not even come from the building electrical power. It might be 'stray voltage' (current flowing through the earth) picked up by the various grounding electrodes, coupled to the water pipes, and leaving things like hose bibs energized relative to the soil near that point.

-Jon

 

[jaggedben]

...

But it is a concern if you are a plumber. As mentioned above, common water piping between buildings can form a low resistance parallel path for neutral current. In some cases plumbers have experienced electric shock when cutting water pipes used as ground electrodes.

...

-Jon

Not to disagree but that is probably happens only because one or another service grounded to the water piping has an open neutral, and that is not 'normal'. And in that case, the amperage on the GEC would likely be more than 1.5A. (Although at my house we are usually consuming only about 1.5A. So if that's all flowing on the GEC, I have a problem.)

As someone said, compare to the neutral current, and the hot current, if possible. If the neutral is zero then any amount of current on the GEC shows an open neutral on the service. If the neutral current is more than the unbalanced current on the hots, that could be someone else's open neutral, especially if roughly the difference is showing on the GEC.

For a 600A service, 1.5A on the neutral is probably not an issue.

 

[infinity]

Not to disagree but that is probably happens only because one or another service grounded to the water piping has an open neutral, and that is not 'normal'. And in that case, the amperage on the GEC would likely be more than 1.5A. (Although at my house we are usually consuming only about 1.5A. So if that's all flowing on the GEC, I have a problem.)

As someone said, compare to the neutral current, and the hot current, if possible. If the neutral is zero then any amount of current on the GEC shows an open neutral on the service. If the neutral current is more than the unbalanced current on the hots, that could be someone else's open neutral, especially if roughly the difference is showing on the GEC.

For a 600A service, 1.5A on the neutral is probably not an issue.

Can you explain why would you assume that a water pipe with a parallel path for the neutral current under normal conditions would have an open neutral?

 

[winnie]

I believe that what jaggedben is saying is that someone getting _shocked_ probably involves both the path through the piping _and_ the open neutral.

If the neutral is intact then it limits the voltage when the pipe is cut.

-Jon

 

[infinity]

I believe that what jaggedben is saying is that someone getting _shocked_ probably involves both the path through the piping _and_ the open neutral.

If the neutral is intact then it limits the voltage when the pipe is cut.

-Jon

Ah you might be correct.
I read it as any current flow near 1.5 amps=open neutral which would necessarily be the case.

 

[jaggedben]

I believe that what jaggedben is saying is that someone getting _shocked_ probably involves both the path through the piping _and_ the open neutral.

If the neutral is intact then it limits the voltage when the pipe is cut.

-Jon

That's exactly what I meant. Thanks.

 

[romex jockey]

Can you explain why would you assume that a water pipe with a parallel path for the neutral current under normal conditions would have an open neutral?

One of the multitude of secondary paths back to the serving Xfomrmer is asking for premium attention....~RJ~

 

[kwired]

One of the multitude of secondary paths back to the serving Xfomrmer is asking for premium attention....~RJ~

Current follows all possible paths, the majority of the current takes the lowest resistance path. A network of metallic municipal water piping may very well be just as low of resistance or even lower in some instances than the service neutral and I could see it easily carrying around same amount of current as the service neutral in that situation.