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  #46  
Old 8/11/17, 7:24 AM
Justin Ake Justin Ake is offline
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Default Re: Sub Panel: Neutrals and grounds on same bus bar Question

Roy,

I think I'd try to use both the professional terminology and the layman's term in parenthesis like you did. Our main goal is to educate our client and if they can't understand what we're saying then we haven't helped them out at all. Plus it helps prevent those follow up clarification calls when the client is trying to describe the deficiencies to their realtor or whoever. I agree the term "ground" can be misused, so throwing EGC in there covers all the bases and makes it simple for the electrician when the client calls one.

Jim,

You mentioned that it may sometimes be ok for the neutral bar to be bonded at the sub. Can you explain a little more please? Here's a pic of a sub I did yesterday (in the same building as main panel) and I called it out b/c the neutral was bonded. Was I correct?
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sub-panel-neutrals-and-grounds-same-bus-bar-question-dsc_0039.jpg   sub-panel-neutrals-and-grounds-same-bus-bar-question-dsc_0040.jpg   sub-panel-neutrals-and-grounds-same-bus-bar-question-dsc_0041.jpg  
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  #47  
Old 8/11/17, 12:41 PM
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Default Re: Sub Panel: Neutrals and grounds on same bus bar Question

Older editions of the code allowed 3 wire feeders to detached structures. The panel needed to be bonded like a service panel.

If the panel is in or on the same building as the service it needs a 4 wire feeder and the neutral is not bonded. You were correct .
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  #48  
Old 8/11/17, 1:26 PM
Justin Ake Justin Ake is offline
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Default Re: Sub Panel: Neutrals and grounds on same bus bar Question

Ok, so that brings up another question. Sorry, but I don't understand why a 3 wire feeder would require bonding at a sub. Once it's bonded, wouldn't that still provide a parallel path for neutral current, regardless of how many wires are used for the hook up?
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  #49  
Old 8/11/17, 3:30 PM
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Default Re: Sub Panel: Neutrals and grounds on same bus bar Question

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Originally Posted by jake1 View Post
Ok, so that brings up another question. Sorry, but I don't understand why a 3 wire feeder would require bonding at a sub. Once it's bonded, wouldn't that still provide a parallel path for neutral current, regardless of how many wires are used for the hook up?
Because it's only a 3-wire feeder. You would have two hot legs and a neutral and that's it. The equipment grounding would be provided by bonding the neutral. This was permitted prior to the 2008 NEC for remote structures.
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  #50  
Old 8/11/17, 4:09 PM
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Default Re: Sub Panel: Neutrals and grounds on same bus bar Question

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Originally Posted by Robert Meier View Post
Because it's only a 3-wire feeder. You would have two hot legs and a neutral and that's it. The equipment grounding would be provided by bonding the neutral. This was permitted prior to the 2008 NEC for remote structures.
Thank you Robert we appreciate you being a member of this board.
Me personally ground rods are cheap. I stick them everywhere .
I don't believe there would ever be a problem with overdoing ground rods. At least down here in Florida . less than two feet down its moist year round.




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Last edited by rlewis5; 8/11/17 at 4:13 PM..
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  #51  
Old 8/11/17, 5:10 PM
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Default Re: Sub Panel: Neutrals and grounds on same bus bar Question

One thing to remember is that ground rods do nothing to trip a breaker.
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  #52  
Old 8/11/17, 5:20 PM
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Default Re: Sub Panel: Neutrals and grounds on same bus bar Question

Jim is the other one. Both give great advice when it comes to electrical.




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  #53  
Old 8/11/17, 5:23 PM
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Default Re: Sub Panel: Neutrals and grounds on same bus bar Question

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One thing to remember is that ground rods do nothing to trip a breaker.
Yes but they do keep transient voltage at bay.
Here in Florida is probably the most lightning prone place in the US. Ground rods are a good thing




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  #54  
Old 8/16/17, 12:51 PM
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Default Re: Sub Panel: Neutrals and grounds on same bus bar Question

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Originally Posted by rlewis5 View Post
Yes it does.
Then there is a serious problem with the system. Residential systems are always solidly grounded. Floating grounds are very rare. In more than 42 years in the electrical trade, having done many hundreds of installations and hundreds of forensic electrical investigations I have never encountered a floating ground in a residential system unless it was damaged.

Look at the utility pole where the transformer is mounted, the meter socket, and the service panels and you will clearly see the system is solidly grounded.



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  #55  
Old 8/16/17, 12:57 PM
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Default Re: Sub Panel: Neutrals and grounds on same bus bar Question

I was referring to floating neutrals in a sub panel. Not the grounding conductors.




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  #56  
Old 8/16/17, 2:30 PM
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Default Re: Sub Panel: Neutrals and grounds on same bus bar Question

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Originally Posted by rlewis5 View Post
I was referring to floating neutrals in a sub panel. Not the grounding conductors.
Neutrals do not float. They are called the grounded conductor because they are solidly grounded. It is only relatively recently that referring to them as neutral conductors has become acceptable. They are truly only neutral in a perfectly balanced 240V circuit. Residential systems are split-phase. In order to have 120V, the grounded conductor is connected to the center of the source transformer's secondary winding. The center tap is always grounded. Hence, the name Grounded Conductor.

Modern residential systems are usually grounded at no fewer than three locations. It is not impossible but it is extremely rare for a system to lose its connection to ground. A system with a floating neutral would require major screw-ups by both the electrician who wired the house and the lineman who installed the source transformer.

When I investigate a fire or electrocution, I am digging deep into the electrical system. I am not doing a casual inspection as I would in a home inspection. I have seen fires caused by loss of the neutral it even in those cases, the neutral was grounded.

My memory is not perfect but I am sure that if I ever encountered a floating neutral in a house, I'd remember it.



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  #57  
Old 8/16/17, 2:35 PM
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Default Re: Sub Panel: Neutrals and grounds on same bus bar Question

So at a subpanel. If I took my ohms meter. And went from the neutral bar to the housing. I should see no deflection. Correct?




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  #58  
Old 8/16/17, 3:09 PM
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Default Re: Sub Panel: Neutrals and grounds on same bus bar Question

Quote:
Originally Posted by rlewis5 View Post
So at a subpanel. If I took my ohms meter. And went from the neutral bar to the housing. I should see no deflection. Correct?
The measurement with an Ohmmeter should be at zero or very close to zero (depending on the accuracy of the meter) if it is grounded. Measuring with an Ohmmeter, a megger, or a hi-pot would also show as open (though using a hi-pot would not be a good idea) if it were floating. If you had a floating neutral, it would be very high, close to infinity. In other words, it would show as an open. If you were to encounter a very high resistance at any given point, you would need to look to see where the connection was lost. Merely losing the connection at one point in the system does not by itself constitute a floating neutral.

It is also possible to lose one or more connections and read low but higher than expected resistance or a resistance of thousands of Ohms. You could, for example read a couple of hundred ohms. One possibility is that you would be reading through connected loads. If you are troubleshooting or trying to determine the cause of a fire, you would need to remove all loads from all circuits.

I've seen houses burn so intensely that the entire house was in the basement. In one such case, I arrived on the scene before the rest of the people I was working with arrived. Within five minutes, I was able to see that the neutral was still solidly grounded. The reason was that it was a pole mounted transformer. The fuse had blown on the transformer as a result of the fire (which was arson) but the transformer was completely intact. There again, that is not to say that the neutral didn't lose its connection to ground somewhere in the house. I was, however, able to determine that they system was solidly grounded as it was supposed to be.

The chances of a home inspector encountering a floating neutral are almost infinitesimally small. If even if you were to find what you suspect may be a floating neutral, the next question is, do you have the skills to make that determination? The typical journeyman or master electrician does not. The typical electrical engineer does not. Properly diagnosing and identifying many electrical deficiencies and defects requires very specialized training and lots of experience. I've been training electricians, electrical technicians, and electrical engineers for decades so I have a pretty good idea of what their training consists of.



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Last edited by gwells; 8/16/17 at 3:18 PM..
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  #59  
Old 8/16/17, 4:02 PM
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Default Re: Sub Panel: Neutrals and grounds on same bus bar Question

Without all the technical babble. So we shouldn't use floating we should use isolated at the sub panel correct?




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  #60  
Old 8/16/17, 4:12 PM
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Default Re: Sub Panel: Neutrals and grounds on same bus bar Question

Mr. Wells I tried to call you from your website phone number. All I got was robotic voicemail. Have a great day




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