Test Question - Troubleshooting

[jxofaltrds]

With the limited information provided what would be your first assumption?
This is a real life problem. So let us see your troubleshooting abilities!



1. Improper bonding in ?sub? panel.
2. Gremlins
3. Dead short
4. Lost leg
5. Lost utility neutral
6. Everything is OK
7. Neighbor lost neutral
8. No big deal lights still work ? see it all the time
9. Current flowing through ground to utility
10. No ground rod present

 

[ActionDave]

My first troubleshooting notion is to ask, "What the heck are we talking about here?"

 

[jxofaltrds]

My first troubleshooting notion is to ask, "What the heck are we talking about here?"

That is part of the point. :slaphead: Just seeing who knows how to troubleshoot - not just cite code!

 

[ActionDave]

I'll play but you have a crude diagram and some ill-defined terms. "Sub Main" what is that? Disconnect? what kind.

There is zero amps on the noodle and four point something going to earth. We are looking at a service???? Is that the nub of it?

 

[Smart $]

With the limited information provided what would be your first assumption? ...

My first assumption (?) to troubleshoot is, I need to take more measurements and determine other facts...

 

[jxofaltrds]

I'll play but you have a crude diagram and some ill-defined terms. "Sub Main" what is that? Disconnect? what kind.

There is zero amps on the noodle and four point something going to earth. We are looking at a service???? Is that the nub of it?

I am not try to insult you or anyone else.

I think that this post proves how few can troubleshoot.

What you see is what I got from the homeowner over the phone. I figured it out 200 miles away. Yet no one locally or the utility could figure it out until pressed (shown/told what to do).

 

[don_resqcapt19]

I agree with Dave...the terms in in your diagram are not clear.
Is the item you call the "disconnect" the service disconnect?
Are the conductors where you show zero current on the neutral the service conductors?
Is the "sub main panel" a second panel fed from the service disconnect?

 

[al hildenbrand]

My first assumption (?) to troubleshoot is, I need to take more measurements and determine other facts...

Agreed.

This is a curiously limited set information. No voltage or phase information. No location information. And two current measurements without attribution (who measured the current and how). While the blue O is probably the energy source, it's not clear what type it is, nor whether there are other panels (not shown) connected to it.

As a troubleshooter, and that Mike is reporting this, I am going to assume that Mike took the current measurements with an ammeter himself in the course of a single family dwelling inspection, that the location is in residential division and the dwelling supplied potable water through a common municipal water utility metal piping system that is connected to the copper water piping in the diagram.

Because Mike is reporting this, I am not at, nor am I likely to have ever been at, the occupancy in question, so, the first thing I want to do is play "20 Questions." But if I can't ask, and, say this is a text, and Mike is asking what to do next, I'd suspect #5 and suggest putting the ammeter back on the three wire neutral and seeing if current will appear when switching off and on loads to test my suspicion.

 

[Ponchik]

I would say Neighbor lost neutral or has loose neutral.

I had this happen to me when i was doing a panel upgrade and I saw sparks when disconnecting the neutral. Both hots were already disconnected with the meter pulled.

 

[Smart $]

I would say Neighbor lost neutral or has loose neutral.

Okay... but then why no neutral current on the local system?

 

[hurk27]

Well my guess is lost utility neutral at the pole/transformer, but since the poll would not allow another answer to be also selected I would also have to select #9 as both should have been within the same answer as they both would happen if you lost the utility neutral.

The 4.8 amps is a throw off because this is the current you would have on a ground rod of 25 ohms with 120 volts applied, but this could only occur if #4 also happened which is the only way you would get a fully unbalanced neutral to provide the 120 volts and the water line had a dielectric coupling blocking it from being a GE and a ground rod was present, or there was 10' of waterline in earth contact that had a 25 ohm resistance and no rod electrode as purported in the graphic.

But the way I see it is the 4.8 amps is only the unbalanced neutral current returning on the GES

To trouble shoot this from an arm chair is a WAG period! as I pointed out above their could be many things that would cause 4.8 amps on the water ground, and we could even be looking at a case where this service is perfectly balanced and a neighbor has lost their neutral, as also pointed out, but not very likely.

Not a very well drawn graphic as much of it is hardly visible, the yellow used for the water GE is almost not readable as to what it is, at first I thought it was a rod GE.

Not a very good test for trouble shooting at least from an arm chair.

 

[hurk27]

Okay... but then why no neutral current on the local system?

You must have posted while I was still writing, good question, even if this house had a balanced service the neighbors house would still put the 4.8 amp on the neutral, so scratch the lost neutral at a neighbors house remark in my last post, so it would have to be a lost neutral at this house, but both #5 and #9 would apply

 

[ActionDave]

I am not try to insult you or anyone else.

I think that this post proves how few can troubleshoot.

What you see is what I got from the homeowner over the phone. I figured it out 200 miles away. Yet no one locally or the utility could figure it out until pressed (shown/told what to do).

You either had some Q&A with the home owner or you took a stab at a solution and got it right.

Care to share some of the conversation?

 

[Smart $]

You must have posted while I was still writing, good question, even if this house had a balanced service the neighbors house would still put the 4.8 amp on the neutral, so scratch the lost neutral at a neighbors house remark in my last post, so it would have to be a lost neutral at this house, but both #5 and #9 would apply

Well, I posed the question to illicit a response... from edward... but yours will do.

Going back to my first response... need more info. Until we take or get more measurements, we cannot assume which has the compromised neutral. As you said, this would be unbalanced current. If this service just happen to have 4.8A of neutral current... of the exact opposite polarity of the neighbor's with a compromised utility neutral... then it is possible.

 

[pjholguin]

I understand what you are asking and don't have a problem with limited information and the diagram.

I would try to get enough information as possible, and then try to deceifer from that. I go with lost it Utility neutral; based on the limit information.

I am not try to insult you or anyone else.

I think that this post proves how few can troubleshoot.

What you see is what I got from the homeowner over the phone. I figured it out 200 miles away. Yet no one locally or the utility could figure it out until pressed (shown/told what to do).

 

[jxofaltrds]

I said that the info was poor. That is how troubleshooting starts some times.

I asked for your best guess.

I wanted to see where you would start your troubleshooting.

Thank you for playing.

Utility connection lost (neutral).

Follow up question. Now that the utility made a repair there is still objectionable current on the copper metal water lines I say that this should be removed by isolating the water lines (10'+; 250.52(A)(1)) outside. One of my concerns is that since the GEC is bare copper and runs in a chase with the interior copper water lines and metal HVAC runs that it 'may' be coming in contact with these interior parts. I say replace it with an insulated GEC (connected within 5'; 250.68(C)(1)) to remove any touch potential on these parts.

Opinions welcome.

 

[Smart $]

...

Follow up question. Now that the utility made a repair there is still objectionable current on the copper metal water lines I say that this should be removed by isolating the water lines (10'+; 250.52(A)(1)) outside. One of my concerns is that since the GEC is bare copper and runs in a chase with the interior copper water lines and metal HVAC runs that it 'may' be coming in contact with these interior parts. I say replace it with an insulated GEC (connected within 5'; 250.68(C)(1)) to remove any touch potential on these parts.

Opinions welcome.

I would say to investigate the source of the objectionable current first. If you replace the GEC with an insulated conductor, you could end up increasing the voltage gradient the MBJ and electrode connection. With the bare GEC touching the water and mechanical lines, it actually serves to reduce the resistance/impedance. Isolating the GEC may increase the resistance/impedance. While this may reduce touch potential on the water and mechanical lines, it my increase touch potential elsewhere.

 

[jxofaltrds]

I would say to investigate the source of the objectionable current first. If you replace the GEC with an insulated conductor, you could end up increasing the voltage gradient the MBJ and electrode connection. With the bare GEC touching the water and mechanical lines, it actually serves to reduce the resistance/impedance. Isolating the GEC may increase the resistance/impedance. While this may reduce touch potential on the water and mechanical lines, it my increase touch potential elsewhere.

This is what I am saying. Only difference is the connection is in the disconnect. How does this code requirement increase risk elsewhere?

 

[Smart $]

This is what I am saying. Only difference is the connection is in the disconnect. How does this code requirement increase risk elsewhere?

View attachment 10815

As pictured, it doesn't...

But you're asking if isolating/insulating the GEC from touching the water lines (beyond 5') and mechanical lines will reduce touch potential. It won't.

 

[infinity]

I said that the info was poor. That is how troubleshooting starts some times.

I asked for your best guess.

I wanted to see where you would start your troubleshooting.

Thank you for playing.

Utility connection lost (neutral).

You gave away the answer too soon, I thought that was obvious with some assumption from the information provided.