grounding panel boards

[kwired]

The main bonding jumper cannot be in the wireway, See 250.24(B). I think that section requires the main bonding jumper to be in the service enclosures. It is true that the GEC can be connected to the grounded conductor in the wireway, but that does not constitute the main bonding jumper. The main bonding jumper's purpose is to connect the grounded conductor to the equipment grounding conductors and the service enclosure.

I agree with you on this.

What is your view on the "taps" that is mentioned in the OP? I feel they are pointless if installed in a manner that creates a parallel path with the grounded service conductor. They would also violate many of the requirements of 310.4.

 

[Smart $]

The main bonding jumper cannot be in the wireway, See 250.24(B). I think that section requires the main bonding jumper to be in the service enclosures. It is true that the GEC can be connected to the grounded conductor in the wireway, but that does not constitute the main bonding jumper. The main bonding jumper's purpose is to connect the grounded conductor to the equipment grounding conductors and the service enclosure.

I agree with you on this.

What is your view on the "taps" that is mentioned in the OP? I feel they are pointless if installed in a manner that creates a parallel path with the grounded service conductor. They would also violate many of the requirements of 310.4.

Well I have some reservations about this whole scenario.

The problem with all these grounded and grounding conductor terms, and where connections are permitted or required to be made, is they all don't fit every situation. eprice points out the MBJ issue for the OP scenario... but that brings up the GEC issue under 250.24(D) which says a GEC shall be used to connect the EGC's, service enclosure(s), and if applicable the grounded service conductor. Under this requirement, an MBJ would be redundant under all situations.

Additionally, as I see it, there are requirements what an MBJ must do and how it is to be installed, but I don't see where an MBJ is actually required to be installed. 250.28 general states an MBJ (and SBJ where applicable) "shall be installed as follows...", but that is not the same as "shall be installed".

Furthermore, we must also adhere to 250.6 regarding objectionable current, most notably 250.6(B).

 

[cripple]

grounding panel boards

The NESC requires utilities to ground there distribution system and the supply to the residential services.
Since the utility?s service supplying the premises wiring system is grounded, the grounded conductor is required to be brought to the service per 250.24(C). 250.24(A) requires a grounding electrode conductor to be connected the service grounded conductor; this connection can be made at any of three accessible locations, at the load end of the service drop, lateral or the service disconnecting means. The main bonding jumper is required per 250.28, because it is served from a grounded system.
250.24(B) requires a main bounding jumper for grounded system and 250.28 has requires for the installation of the main bounding jumper and system bounding jumper for grounded systems.
250.64(D)(3) permits the grounding electrode conductor to be located in a common location, and is required to be sized in accordance to 250.66 based on the service-entrance conductor(s) at the common location where the connection is made.
In is scenario two grounding electrode conductor are installed, one in wireway and the other in the 100 amp panelboard. The grounding electrode tap conductor is required per NEC, but a main bounding jumper is at each panelboard.

 

[eprice]

What is your view on the "taps" that is mentioned in the OP? I feel they are pointless if installed in a manner that creates a parallel path with the grounded service conductor. They would also violate many of the requirements of 310.4.

I see it the same way.

Well I have some reservations about this whole scenario.

The problem with all these grounded and grounding conductor terms, and where connections are permitted or required to be made, is they all don't fit every situation. eprice points out the MBJ issue for the OP scenario... but that brings up the GEC issue under 250.24(D) which says a GEC shall be used to connect the EGC's, service enclosure(s), and if applicable the grounded service conductor. Under this requirement, an MBJ would be redundant under all situations.

In the case of a grounded service, 250.24(A) and (B) seem to work well together, but (D) throws in some confusion as you pointed out. In the case of an ungrounded service, (A) and (B) don't apply, so (D) and (E) seem to cover what is needed. I think (D) needs to be reworded to remove the confusion that it causes in the case of a grounded service.

Additionally, as I see it, there are requirements what an MBJ must do and how it is to be installed, but I don't see where an MBJ is actually required to be installed. 250.28 general states an MBJ (and SBJ where applicable) "shall be installed as follows...", but that is not the same as "shall be installed".

250.24(B) says it "shall be used to...". I think that is close enough to "shall be installed". It can't be used to do what that section requires it to do if it isn't installed.

 

[Smart $]

I see it the same way.
...
250.24(B) says it "shall be used to...". I think that is close enough to "shall be installed". It can't be used to do what that section requires it to do if it isn't installed.

I'll go with 250.24(B) as requiring the MBJ to be installed... BUT that don't eliminate the 250.24(D) redundancy, which by the way would again create a parallel path for neutral current if the 250.24(D) were complied with and an MBJ installed. Also, 250.6 can overide 250.24(B) for certain installations where objectionable current would exist by installing an MBJ. So it is but it 'ain't' required to be installed. We could use non-conductive raceway or cable sheath methods just so we can install an MBJ... but 250.6 does not say we have to. This is what I'm referring to as not being required to be installed under 250.6 conditions.

You can say 250.24(D) needs to be reworded to eliminate the confusion, but who is to say it is the problem. IMO, the MBJ leads to confusion moreso than a GEC bonding the grounded with the grounding (one less term to deal with ).