Grounding Electrode Conductor Requirements

[minesh21]

I'm confused on when a contractor will need to connect an electrode grounding conductor from a sub-panel to ground for panelboards that are NOT the service. When I walk some areas I notice that all panelboards are connected to a grounding bus bar via electrode grounding conductor. Then I walk other areas (usually remote areas not in electrical rooms) where this is not the case. It's confusing on exactly when you should be installing this electrode conductor.

Typically you have an equipment grounding conductor that is installed in all conduit to equipment for bonding. So you are creating an effective ground fault current path with all equipment in the case where there is a ground fault that energizes the case of metallic equipment. This goes to either a transformer (separately derived system) or the service. At the separately derived source (or service) is where the neutral and ground get connected to complete this path and allow for the functioning of breakers to open and clear the fault. Also, at this point is where the bonding jumpers are installed and the electrode ground conductor is connected to building steel, metal water pipe, ground rod, etc.. I don't think you need to install this same electrode grounding conductor to downstream lighting and appliance panelboards. It doesn't quite make sense, other than trying to create a stronger equipotential point. So are these electrode conductors to ground bars installed just for equipotential? If this is required to limit voltage to ground then shouldn't ALL panelboards have this?

 

[jap]

when a contractor will need to connect an electrode grounding conductor from a sub-panel to ground for panelboards that are NOT the service.

If all the subpanels are in the same structure, I say never.

JAP>

 

[publicgood]

You must for buildings fed by feeders. Otherwise, not required by code. Not restricted by code either.

You may choose to do this rather than having equipment grounds between panels - VE consideration. I see this frequently outside of the states. Doing otherwise is redundant and necessarily adding cost to the project.

 

[jumper]

You may choose to do this rather than having equipment grounds between panels

Please clarify this. I am hoping I am misreading what you are saying.

 

[minesh21]

Please clarify this. I am hoping I am misreading what you are saying.

I believe he's saying you can save cost by grounding all the panels in the same area to a common ground bar rather than running equipment grounding conductors everywhere. However, I always design for equipment grounding conductors for bonding.

 

[electrofelon]

I believe he's saying you can save cost by grounding all the panels in the same area to a common ground bar rather than running equipment grounding conductors everywhere. However, I always design for equipment grounding conductors for bonding.

I am not exactly sure what you are proposing, but it is likely a violation. Almost all of the time, the egc has to be in the same conduit or cable as the other circuit conductors.

 

[minesh21]

I am not exactly sure what you are proposing, but it is likely a violation. Almost all of the time, the egc has to be in the same conduit or cable as the other circuit conductors.

It's not what I am proposing. I'm just saying that may be what the other user was implying. Like I said, I always design for equipment grounding conductors in all conduit...

 

[kwired]

I'm confused on when a contractor will need to connect an electrode grounding conductor from a sub-panel to ground for panelboards that are NOT the service. When I walk some areas I notice that all panelboards are connected to a grounding bus bar via electrode grounding conductor. Then I walk other areas (usually remote areas not in electrical rooms) where this is not the case. It's confusing on exactly when you should be installing this electrode conductor.

Typically you have an equipment grounding conductor that is installed in all conduit to equipment for bonding. So you are creating an effective ground fault current path with all equipment in the case where there is a ground fault that energizes the case of metallic equipment. This goes to either a transformer (separately derived system) or the service. At the separately derived source (or service) is where the neutral and ground get connected to complete this path and allow for the functioning of breakers to open and clear the fault. Also, at this point is where the bonding jumpers are installed and the electrode ground conductor is connected to building steel, metal water pipe, ground rod, etc.. I don't think you need to install this same electrode grounding conductor to downstream lighting and appliance panelboards. It doesn't quite make sense, other than trying to create a stronger equipotential point. So are these electrode conductors to ground bars installed just for equipotential? If this is required to limit voltage to ground then shouldn't ALL panelboards have this?

If you have separately derived systems you do need to connect that system to the grounding electrode system, but that doesn't mean drive a local rod at the separately derived system it means tie to the GES of the entire building. Structural steel is a great place to tie this when present.

If you have a single voltage system on the premises and all your "sub panels" are simply feeders to various locations in the same structure - all you need is an equipment grounding conductor with the feeder (which can be a metal raceway). A feeder to a separate building/structure will require a grounding electrode system at that separate structure.

 

[minesh21]

If you have separately derived systems you do need to connect that system to the grounding electrode system, but that doesn't mean drive a local rod at the separately derived system it means tie to the GES of the entire building. Structural steel is a great place to tie this when present.

If you have a single voltage system on the premises and all your "sub panels" are simply feeders to various locations in the same structure - all you need is an equipment grounding conductor with the feeder (which can be a metal raceway). A feeder to a separate building/structure will require a grounding electrode system at that separate structure.

Perfect this is what I was thinking. Thanks!

 

[Dennis Alwon]

You can choose to run an grounding electrode conductor to the primary building instead of an equipment grounding conductor as long as it is sized appropriately. Thus the grounding electrode conductor serves as an equipment grounding conductor also. The grounding electrode conductor must be connected to the electrodes.

 

[minesh21]

You can choose to run an grounding electrode conductor to the primary building instead of an equipment grounding conductor as long as it is sized appropriately. Thus the grounding electrode conductor serves as an equipment grounding conductor also. The grounding electrode conductor must be connected to the electrodes.

I'm not sure I understand what you're saying. The grounding electrode conductor is different than the equipment grounding conductor, not only in sizing but also in utilization and purpose. The grounding electrode conductor is connected directly to grounding electrode(s), while the equipment grounding conductor is used for bonding. They are not the same or interchangeable.

 

[jumper]

I'm not sure I understand what you're saying. The grounding electrode conductor is different than the equipment grounding conductor, not only in sizing but also in utilization and purpose. The grounding electrode conductor is connected directly to grounding electrode(s), while the equipment grounding conductor is used for bonding. They are not the same or interchangeable.

There are a few exceptions where a conductor can be both at times, but it is confusing as all get out and I just ignore them. I have never needed nor wanted to figure the exceptions.

 

[publicgood]

Please clarify this. I am hoping I am misreading what you are saying.

Yes, clarification is needed here. As a follow-up, I agree this would not be code compliant for the NEC, but is often compliant and seen for foreign codes outside the US.

From an application rather than a code standpoint, I’d have to think about it a little more. This is not a great idea for ground fault, but operationally not a terrible idea otherwise. From a long term standpoint certainly worry-sum that one disconnection might render several circuits without equipment grounds.

 

[kwired]

Yes, clarification is needed here. As a follow-up, I agree this would not be code compliant for the NEC, but is often compliant and seen for foreign codes outside the US.

From an application rather than a code standpoint, I’d have to think about it a little more. This is not a great idea for ground fault, but operationally not a terrible idea otherwise. From a long term standpoint certainly worry-sum that one disconnection might render several circuits without equipment grounds.

Are you talking about this:

I believe he's saying you can save cost by grounding all the panels in the same area to a common ground bar rather than running equipment grounding conductors everywhere. However, I always design for equipment grounding conductors for bonding.

Not exactly NEC compliant but still much better method then driving ground rods and thinking that will function as what NEC calls "equipment grounding conductor".