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Old 01-09-2012, 12:39 AM   #166
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Need to know if my grounds and neutrals are connected right


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Thanks for taking the time to draw it out Stubbie. I for one learn much easier with pictures and drawings vs. written words.
Your welcome .. any questions ?

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Old 01-09-2012, 04:53 AM   #167
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Need to know if my grounds and neutrals are connected right


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Your welcome .. any questions ?
Thanks for asking but I'm ok here. I think your last post grew somewhat so I went back and read some more.

I'm very interested in 3 wire service extensions but I still need to read the code that you pointed me to. I started a pedestal thread if you care to look it over and make sure I'm not heading in the wrong direction.

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Old 01-09-2012, 09:28 AM   #168
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Need to know if my grounds and neutrals are connected right


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Thanks for asking but I'm ok here. I think your last post grew somewhat so I went back and read some more.

I'm very interested in 3 wire service extensions but I still need to read the code that you pointed me to. I started a pedestal thread if you care to look it over and make sure I'm not heading in the wrong direction.
Ok I'll take a look at it .

Sorry about the long post but the subject we are talking about with the OP is not one that can be explained easily in a few sentences. It's going to take a while if he is interested. My hope is he can see the danger in the way he is wiring his barn panel to direct ground fault current to earth via his grounding rod. He is thinking and evidently listening to locals telling him this is how it should be done.

I'll post a illustration of his barn panel showing where he has made a serious error by thinking the ground rod (earth) is what is needed to protect him from ground faults like a hot wire coming in contact with the metal of his barn panel. Understand though he has run his feeder from a panel other than the service equipment and would be required to run a 4 wire feeder to his barn. However he ran a 3 wire feeder from that house panel so the illustration is showing what is wrong with his barn panel bonding based on a proper and code compliant 3 wire feeder.

The red dots show the only path available for a ground fault on the branch circuit is to earth. If that happens the barn panel metal and any other bonded metal on that branch circuit is going to reach 120 volts and the breaker will not have enough current flow through it to trip out and de-energize the circuit. The earth will not allow enough current to flow at 120 volts with the resistance it imposes.
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Old 01-09-2012, 09:45 AM   #169
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Need to know if my grounds and neutrals are connected right


The scariest thing about this thread is the school electrician that told him 3 wire is correct. He has been doing it for many years and probably will not change. That sounds very familiar in many professions. Sad they do not keep up with changes.
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Old 01-09-2012, 07:37 PM   #170
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Need to know if my grounds and neutrals are connected right


While I certainly hope the o. p. takes the advice offered in this thread by all you very knowledgeable and professional people, I will also say that, because of his stubborness, this thread has become the most interesting and informative one I have ever read. Thank you all for the lesson. Everyday I learn how much I do not know.
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Old 01-09-2012, 07:55 PM   #171
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Need to know if my grounds and neutrals are connected right


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Everyday I learn how much I do not know.
I feel the same way! But I always love learning things I don't know!
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Old 01-09-2012, 09:34 PM   #172
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Need to know if my grounds and neutrals are connected right


There seems to be enough interest by other people that I'll go ahead and finish out what I intended.

So I guess the best thing to do is discuss another diagram. What this diagram shows is the path the NEC refers to as "the effective ground fault path". Which is essentially a low impedance path that will complete a circuit with a hot wire over the equipment ground wires and bonded metal of your branch circuit in the event of a ground fault. An example would be as shown in the diagram. When the hot wire contacts the metal device box it immediately energizes the box and fault current flows over the intentionally constructed 'effective ground fault path" as it seeks the transformer (*source). Since there is no load to limit the current massive amps will flow on the completed fault path circuit. These amps must pass thru the circuit breaker protecting the branch circuit where the fault has occurred and it opens on overcurrent and de-energizes the circuit.

The key point here is that only one low impedance path exists from the service equipment to the center tap of the transformer and that is the service neutral. Because of this both fault current and neutral current must use this link to get to the transformer. How we make sure that happens is to bond both neutral and ground to the service neutral (grounded conductor) at the service equipment.

So it is critical that this low impedance "effective ground fault path" is unbroken so that a circuit breaker can clear the ground fault once the fault circuit energizes. If you notice the effective ground fault path runs parallel to the neutral (grounded leg) of the branch circuit but never connects to or contacts the neutral until it bonds with it at the service equipment before reaching the transformer. So the purpose of the equipment grounding system (EGS) is to bond all metal likely to be energized in a ground fault to the effective ground fault path so that a circuit breaker will trip and clear the fault.

The principal point I'm making here is that you never bound neutral and ground after the service equipment (load side). If you do then you will allow neutral current to use the effective ground fault path where it is unwanted and dangerously unexpected as it returns to the source. The effective ground fault path is only there to complete a circuit with the transformer in the event of a fault with a hot wire to bonded metal or equipment ground wires. It plays no part other than human safety during the typical operation of your electrical system.

The last thing to picture in your head is opening or breaking that effective ground fault path. So picture removing the equipment ground wire of the branch circuit shown at the service equipment neutral bar where it bonds with the grounded conductor of the utility. You have effectively opened the fault circuit and all metal that is likely to be energized at the origin of the fault (metal device box) to the service equipment will come to line voltage of 120 volts and a breaker cannot trip as there will be no current flow due to the loss of the effective ground fault path.
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Old 01-10-2012, 01:27 PM   #173
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Need to know if my grounds and neutrals are connected right


I think I will just summarize the OP's situation and then post a couple diagrams.

1.) Dorlow has an unknown wiring issue at his service equipment ... there are 5 wires entering from the meter socket ... should only be 3 wires.

2.) 4 wires feed the interior house load center .. which is correct.. however the panel has bonded neutral and ground (you never do this on 4 wire feeders) and is allowing neutral current to utilize the feeder ground coming fron the service equipment to return to the source. This is a dangerous and major code violation. Also notice that at his service equipment the egc is connected to the grounding lug and will need to utilize the metal of the enclosure to reach the service neutral .. another code violation.

3.) 3 wire feeder to sub-panel installed next to 1st sub-panel that feeder needs to be 4 wire which mandatory by code. That feeder needs to be in conduit due to individual wires... big violation. Also even though it is 3 wire feeder he does not have his bonding means installed to the metal of the sub-panel. Any fault to that metal will energize it and a breaker will not trip.

4.) 3 wire feeder to barn panel. Since the feeder originates from a sub panel other than the service equipment it is required to be 4 wire for a couple reasons. One .. all panels after the service equipment that are installed in the same structure as the service equipment require 4 wire feeders. Due to this requirement neutral and ground must be separated (not bonded). If you bond them then you have created a parallel path for neutral current to use metal and the equipment ground of the feeder to return to the source transformer. So the barn panel feeder originates in a panel that is required to be served by a 4 wire feeder therefore the feeder to the barn panel must be 4 wire. The 3 wire exception allowed in 2005 and prior does not apply. It would only be possible if the feeder originates at the service equipment.

5.) Barn panel is wired to direct fault current to ground (earth) due to improper bonding. Assuming this was a code compliant 3 wire feeder if an inspector saw this he probably would put a work stoppage tag on the permit and require an electrician to finish the job. As it is the entire installation from the service equipment to the barn shows a total lack of understanding.

Ok diagrams ... first one is a improperly bonded 3 wire feeder from the service equipment to a detached building. Second one is a improper 4 wire feeder to same.
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Need to know if my grounds and neutrals are connected right-unbonded-3-wire-sub-panel.jpg   Need to know if my grounds and neutrals are connected right-4-wire-improper-bonding.jpg  
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Old 01-10-2012, 02:41 PM   #174
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Need to know if my grounds and neutrals are connected right


Stubbie, that was a very nice piece of writing, and I certainly appreciate it. I do have a question. You, and everyone else who appears to know anything about standard wiring, state:

"2.) 4 wires feed the interior house load center .. which is correct.. however the panel has bonded neutral and ground (you never do this on 4 wire feeders) and is allowing neutral current to utilize the feeder ground coming fron the service equipment to return to the source. this is a dangerous and major code violation."

I have emphasized the last part of the sentence. I understand this is a violation of CURRENT code, but as you and others have pointed out, it is NOT a violation of historical code more than say 10 years old. The part I am a bit puzzled about is the claim that returning current on the independent equipment ground is dangerous.

EXACTLY why is it dangerous? Let's look at this question with an open mind, and ignore the fact that it is a violation of code. First off, the IEG is at least in theory at zero potential, just like the neutral, since it is bonded to the neutral at the service entrance, and has little resistance. In practice then, even if you touched the IEG and it was carrying neutral current, you would receive at most a slight tingle, assuming you are at zero potential (you are grounded). This is of course no different than if you touched the neutral wire, or a piece of equipment that the neutral was touching (assuming a neutral fault condition).

So the fact that the IEG is carrying current at zero potential is not going to harm you (at least in theory) if you touch it. Let's see if there is some other problem with the IEG carrying current. Well, it might be undersized to carry the current. This could be an issue, possibly it will get too hot and will damage insulation. I can see that possibility.

The IEG is not designed to carry current under normal conditions. I get that. But that is a far distance from proving that it is dangerous for the IEG to carry current during normal conditions. My question is, if the IEG were sized the same as the neutral, and perhaps insulated like the neutral, what would be dangerous about allowing it to act as a parallel neutral path under normal conditions?
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Old 01-10-2012, 03:53 PM   #175
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Need to know if my grounds and neutrals are connected right


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My question is, if the IEG were sized the same as the neutral, and perhaps insulated like the neutral, what would be dangerous about allowing it to act as a parallel neutral path under normal conditions?
If the neutral wire was to come loose (a common problem because some people do not torque the lugs to the proper tightness as they should), there would be no indication there was a problem with the electric system.

And likewise, if the ground wire was to come loose, testers would indicate the ground was OK.

It is for the same reason(s) there is a separate ground wire to each outlet.
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Old 01-10-2012, 04:10 PM   #176
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Need to know if my grounds and neutrals are connected right


BillyBob, there would be no indication of a neutral fault based on performance of the equipment, because it would still run. This is correct.

Similarly, if the IEG becomes disconnected, and you have a current code compliant installation, there is no indication of a problem, because the equipment continues to operate even though you no longer have a functional IEG. The only way to tell would be to run a ground fault test on the wire. Of course, this is rarely done except when there is a problem, so I maintain that under current code, there is no obvious indication that an IEG has come loose until you need it, when of course it may be too late.

So are you saying that an undetected neutral fault is somehow more dangerous than an undetected IEG fault? And in the situation I presented, where the two are bonded at the equipment, you could argue that the presence of a parallel path was actually safer than independent paths, because equipment would continue to operate even in the event of a fault on either the neutral or the IEG, and if they both faulted, then the equipment would not operate.
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Old 01-10-2012, 07:14 PM   #177
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Need to know if my grounds and neutrals are connected right


Hi Dan

Excellent question BTW ...

One clarification it's the EGC ...

Your actually close to correct especially at the service equipment where you should have very close to zero potential between neutral and ground. As you move farther away there will some potential due to voltage drop. You could be shocked if you put yourself in series with the neutral under load or contacted the neutral or the energized EGC and another low impedance path that returned to the transformer. Other wise you likely would not be harmed under normal conditions. The farther away you get from the service equipment the more likely you are to come in contact with any objectionable neutral current on metal or the egc.. Metal conduits are especially suspect. As you know it doesn't take a lot of current and voltage to electrocute you.

This diagram from mike holt closely shows what the op in this thread has going on ... however you are correct as your question is ....

Quote:
My question is, if the IEG were sized the same as the neutral, and perhaps insulated like the neutral, what would be dangerous about allowing it to act as a parallel neutral path under normal conditions?
Very little danger provided we are not way downstream of the service equipment where human contact with bonded metal is increased and voltage drop is increased. An insulated egc also helps. However even though it is insulated the metal it bonds is not.

The other danger for humans is getting yourself in series with this current.

I still stand behind it being dangerous both in fire hazard and human safety. As BB said an open neutral between panels with 4 wire feeders that have neutral to ground bonds will never let you know that your metal and EGC is energized with neutral current.

I do hope you understand that neutral current will kill you .. I am assuming here you are taking issue with the fact that I'm saying it is a dangerous situation for human safety.
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Old 01-10-2012, 07:27 PM   #178
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Need to know if my grounds and neutrals are connected right


Objectionable current...

So far the discussion has been regarding the load side of the service disconnecting means. I think it is interesting that anything on the line side of a service (including meter sockets, troughs, cabinets, etc) is normally bonded to nuetral. I think it is odd that it is OK to have that objectionable current on a metal raceway that extends between a meter socket and a main service panel, when it is taboo to have it on feeder conduits.
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Old 01-10-2012, 07:39 PM   #179
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Objectionable current...

So far the discussion has been regarding the load side of the service disconnecting means. I think it is interesting that anything on the line side of a service (including meter sockets, troughs, cabinets, etc) is normally bonded to nuetral. I think it is odd that it is OK to have that objectionable current on a metal raceway that extends between a meter socket and a main service panel, when it is taboo to have it on feeder conduits.
I see your point but somethings just can't be perfect and the code is trying to minimize the risk as much as possible. The panel needs to be bonded to the neutral for safety and it can't be done any further back towards the meter socket/transformer. I guess you could continue this scenario all the way back to the generator.

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Old 01-10-2012, 08:11 PM   #180
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Need to know if my grounds and neutrals are connected right


I think what I mean to say is that it protects the general public as much as possible from things they come in contact with.

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