neutral bus bonding question (Moved from another thread)

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It is a starting point for the equipment grounding conductor network.

Next option (which in some ways might be better) is to run the equipment grounding conductor all the way to the source, but unfortunately the POCO's use the grounded conductor to bond non current carrying metal objects and will not run a separate EGC to the service point.
 
kwired said:
It is a starting point for the equipment grounding conductor network.

Next option (which in some ways might be better) is to run the equipment grounding conductor all the way to the source, but unfortunately the POCO's use the grounded conductor to bond non current carrying metal objects and will not run a separate EGC to the service point.
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I have often wondered why it is that the POCO has effectively bonded the N to the earth at the pole, so why do we do it again? Is their bond not good enough?
 
petersonra said:
I have often wondered why it is that the POCO has effectively bonded the N to the earth at the pole, so why do we do it again? Is their bond not good enough?
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Seems to me that rebonding at the service helps ensure the integrity of the system grounding, instead of just relying on the wire running down the pole to the ground rod. Should someone cut that, you would lose your grounded system if you didn't have the 2nd connection at the service.
 
Since we do not bring an EGC in with the service conductors, there would be no fault clearing path if the neutral was not bonded to the EGCs at the service equipment.
 
don_resqcapt19 said:
Since we do not bring an EGC in with the service conductors, there would be no fault clearing path if the neutral was not bonded to the EGCs at the service equipment.
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But the earth electrode connection does not play any significant part in that fault clearing path.
The bond is what does it.
 
Bonding to the panelboard connects the neutral bus to the EGC bus, which is typically machine screwed directly to the enclosure. Technically, this method of bonding is only compliant in SUSE panelboards. This bonding must meet the requirements of the Main Bonding Jumper for services or the System Bonding Jumper for Separately Derived Systems.

If one happened to use an isolated EGC bus, bonding the panelboard enclosure is still required, but only under EGC requirements.
 
GoldDigger said:
But the earth electrode connection does not play any significant part in that fault clearing path.
The bond is what does it.
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The building could be far from the utility transformer, the grounding electrode connection at the service is no different than the requirement at a separate building.
 
lauraj said:
The building could be far from the utility transformer, the grounding electrode connection at the service is no different than the requirement at a separate building.
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Under Code GEC's are to be connected to the neutral, not the panel enclosure or EGC bus... so the GES plays no role in the service panel bond to the EGC bus via the panel enclosure.
 
petersonra said:
I have often wondered why it is that the POCO has effectively bonded the N to the earth at the pole, so why do we do it again? Is their bond not good enough?
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Might have to move this post to a new thread just like the OP of this thread was moved:)

POCO connects their grounded conductor to an an electrode at nearly every structure within the system. The electrode at every service is just one more electrode in a network of thousands of electrodes. That large network does have a low impedance to earth, but most of the individual electrodes alone have somewhat high resistance.

A grounding electrode is more for high voltage transients whether it be lightning or even if a POCO primary conductor contacts the low voltage distribution then it is for any direct benefit of the low voltage system within the building being served.
 
Since the neutral (i.e. the grounded conductor) is grounded at the source (transformer), if exposed metal parts are not connected to the neutral and they become energized by an ungrouded conductor, they could pose a shock hazard to anyone standing on the ground. So that is the main reason we bond all the exposed metal electrical parts to the neutral at the service; doing so makes it likely that an overcurrent device will trip and remove the shock hazard. The reasons we ground the neutral again at the service are somewhat different, see kwired's comments.

There are other ways to handle electrical system grounding (aka earthing), and other countries do it differently from us. See https://en.wikipedia.org/wiki/Earthing_system

If I understand correctly, TT systems do not bond anything to any current carrying conductor at the service. France and Japan have TT networks.
 
The actual job l' m doing is on a trailer. The service conductors coming from the transformer are run under ground. They did run a separate ground with the grounded conductor( neutral) and ungrounded conductors. I checked for continuity at the service and there was good continuity. Is it still necessary to bond the neutral buss to the panel? Thanks

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chuckgassmannm said:
The actual job l' m doing is on a trailer. The service conductors coming from the transformer are run under ground. They did run a separate ground with the grounded conductor( neutral) and ungrounded conductors. I checked for continuity at the service and there was good continuity. Is it still necessary to bond the neutral buss to the panel? Thanks

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If by trailer you mean mobile home, then you do not bond the neutral to the panel inside the trailer. The only place a grounded [neutral] conductor or bus is bonded to the EGC bus (by way of the panel enclosure in many panelboards) is within the service disconnecting means enclosure. The service disconnecting means for a mobile home cannot be in or on the trailer.
 
I appreciate your help. As far as I can tell the meter box which is next to the transformer( located near the street) doesn't have a disconnect. I'm assuming it's bonded there.

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chuckgassmannm said:
I appreciate your help. As far as I can tell the meter box which is next to the transformer( located near the street) doesn't have a disconnect. I'm assuming it's bonded there.

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If you are supplying a mobile home you need a service disconnecting means not in or on the home, and within 30 feet of the mobile home.
 
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