bonding of the ground and neutral at more then one point

[mschooler2011]

so im still fairly new to the electrical trade since the end of 2011 and theres a lot im still learning and wanting to learn but my question is about the bonding of the neutral and ground in the electrical service. now ive been under the impression you only make this bond once in the service unless down the line a separately derived power source is installed. for example a transformer but other then that im clueless and ive looked it up in the code and the best article I could find was 250.24 in the 2011 nec. but it still didn't really answer my question on if u can make that bond more then once in one service? so I thought u guys could help me out with an answer and maybe a code reference if possible?

 

[LEO2854]

so im still fairly new to the electrical trade since the end of 2011 and theres a lot im still learning and wanting to learn but my question is about the bonding of the neutral and ground in the electrical service. now ive been under the impression you only make this bond once in the service unless down the line a separately derived power source is installed. for example a transformer but other then that im clueless and ive looked it up in the code and the best article I could find was 250.24 in the 2011 nec. but it still didn't really answer my question on if u can make that bond more then once in one service? so I thought u guys could help me out with an answer and maybe a code reference if possible?

Hello...

Welcome to the forum and the electrical trade...:thumbsup:

250.24(A)(1) ..means that you are bonding your neutral and your grounding conductors at the service disconnect,your neutral must not be grounded anywhere else otherwise fault current will not trip the main disconnect or any of the other circuit breakers or fuses in the main panel.

Now in the case of a transformer creating a new service in a building such as a store in a mall then your neutral and ground will be bonded in the transformer .

I've been wrong before but I'm sure this is the case..:lol:


250.24 Grounding Service-Supplied Alternating-Current Systems.
(A) System Grounding Connections. A premises wiring system supplied by a grounded ac service shall have a grounding electrode conductor connected to the grounded service conductor, at each service, in accordance with 250.24(A)(1) through (A)(5).

(1) General. The grounding electrode conductor connection shall be made at any accessible point from the load end of the service drop or service lateral to and including the terminal or bus to which the grounded service conductor is connected at the service disconnecting means.

Informational Note:  See definitions of Service Drop and Service Lateral in Article 100.

 

[augie47]

250.24 also goes on to say:
(5) Load-Side Grounding Connections. A grounded conductor shall not be connected to normally non?currentcarrying metal parts of equipment, to equipment grounding conductor(s), or be reconnected to ground on the load side of the service disconnecting means except as otherwise permitted in this article.
Informational Note: See 250.30 for separately derived systems,
250.32 for connections at separate buildings or structures,
and 250.142 for use of the grounded circuit conductor
for grounding equipment.

 

[qcroanoke]

Very good answers!

 

[meternerd]

250.24(A)(1) ..means that you are bonding your neutral and your grounding conductors at the service disconnect,your neutral must not be grounded anywhere else otherwise fault current will not trip the main disconnect or any of the other circuit breakers or fuses in the main panel.

I'm NOT being picky....I just have a question. If the breakers in the service panel are in series with the line (hot) wires only, wouldn't the fault current be the same whether or not the return current was by way of a neutral bond in the service disconnect panel or an aditional path through a downstream bond? I thought the rule was to prevent parallel ground return paths from carrying normal neutral current.

I'm a utility guy, so Code sometimes confuses me. Be gentle.

 

[don_resqcapt19]

Multiple points of connecting between the grounded and grounding conductors are permitted on the line side of the service disconnect(s). In the case of multiple service disconnects in individual enclosures, multiple bonds are required. Additional bonds on the load side of the service disconnect(s) are not permitted unless they are on the load side of a SDS.

 

[don_resqcapt19]

... your neutral must not be grounded anywhere else otherwise fault current will not trip the main disconnect or any of the other circuit breakers or fuses in the main panel. ...

Multiple neutral to ground bonds will not affect the operation of the OCPDs. The same amount of fault current will flow through the breaker or fuse, no matter how many neutral to ground bonds are installed.

 

[templdl]

250.24(A)(1) ..means that you are bonding your neutral and your grounding conductors at the service disconnect,your neutral must not be grounded anywhere else otherwise fault current will not trip the main disconnect or any of the other circuit breakers or fuses in the main panel.

I'm NOT being picky....I just have a question. If the breakers in the service panel are in series with the line (hot) wires only, wouldn't the fault current be the same whether or not the return current was by way of a neutral bond in the service disconnect panel or an aditional path through a downstream bond? I thought the rule was to prevent parallel ground return paths from carrying normal neutral current.

I'm a utility guy, so Code sometimes confuses me. Be gentle.

Remember that the neutral is a current carrying conductor which is grounded at a single point at the service entrance.
Should you ground the neutral you have now created an addition path for the neutral currents path back to the service entrance. The ground really isn't intended to be a current carrying conductor. Also, anything the uses the third ground connection in a plug will exposed the user to any neutral current flowing so the ground conductor and anything else that happens to be bonded to the ground in conductor.
So, no, regrounding the neutral conductor is not a good thing and can actually cause a shock hazard.