Question on 408.40

[trojans4]

408.40 states in part "Equipment grounding conductors shall not be connected to a terminal bar provided for grounded conductors unless the bar is identified for the purpose and is located where interconnection between equipment grounding conductors and grounded conductors and grounded circuit conductors is permitted or required by Article 250". On a residential/commercial 200A main service panel my understanding is that the neutrals and grounds should land on separate terminal bars even though both terminal bars are bonded to the panel with the reason being there are different termination requirements for grounds and neutrals as pointed out in this article and Article 408.41. My question is about the bold portion. How would a bar be identified for this purpose? What kind of bar would allow both grounds and neutrals to be terminated on it? In a discussion with other electricians I know, resulting from a post on another site, I have been told all terminal bars are listed for either neutrals or grounds so you do not have to have two separate terminal bars in the main panel. I think they are mistaken and am wondering what experts on this forum have to say.

 

[Smart $]

Technically speaking, a grounded conductor bus terminal bar and an equipment grounding bus terminal bar are required to be on opposite sides of the main bonding jumper.

 

[kwired]

Technically speaking, a grounded conductor bus terminal bar and an equipment grounding bus terminal bar are required to be on opposite sides of the main bonding jumper.

How does that work with panels that use a strap type bonding jumper that fits under the same stud the main neutral lug is bolted to? Recent Square D NQ, NF and even I-line panels I have encountered are all like that for a 400 amp panel anyway. Some "loadcenter" panels don't work out very well with that theory of the other side of the bonding jumper either.

I think listing included instructions for most panel neutral bars state you can land EGC's on them if properly used as service equipment.

The bar itself is often the same construction type as the EGC bars for small (200 or less amp) capacity panels anyway.

 

[Smart $]

How does that work with panels that use a strap type bonding jumper that fits under the same stud the main neutral lug is bolted to? Recent Square D NQ, NF and even I-line panels I have encountered are all like that for a 400 amp panel anyway. Some "loadcenter" panels don't work out very well with that theory of the other side of the bonding jumper either.

I think listing included instructions for most panel neutral bars state you can land EGC's on them if properly used as service equipment.

The bar itself is often the same construction type as the EGC bars for small (200 or less amp) capacity panels anyway.

You can twist it any way you want, but you can't change this...

Bonding Jumper, Main. The connection between the
grounded circuit conductor and the equipment grounding
conductor at the service.

 

[kwired]

You can twist it any way you want, but you can't change this...

I wasn't twisting anything - I think.

I may have been overthinking the GC and EGC being on different sides of the bonding jumper to some extent, (I was thinking physical layout more so then electrical characteristics of the bonding jumper, my bad there) but I still believe the EGC can be on either side, but the GC can not be.

 

[mwm1752]

The Bonding Jumper Main is sometimes the bolt that connects to the frame leaving the factory installed buss to be used by both conductors. Generally a single conductor for GC is limited to the connection point -- If you installed a EGC kit attached to the metal frame you would not attach a GC to it only EGC.

 

[Smart $]

I wasn't twisting anything - I think.

I may have been overthinking the GC and EGC being on different sides of the bonding jumper to some extent, (I was thinking physical layout more so then electrical characteristics of the bonding jumper, my bad there) but I still believe the EGC can be on either side, but the GC can not be.

You have that backwards. 250.24(A)(4) paraphrased says where the main bonding jumper is a wire or busbar, the GEC can connect to the EGC bus terminal bar.

The rationale that EGC's can be connected to the grounded conductor bus at the service is the same that hacks connect grounded to grounding and vice versa at the load end of circuits.

 

[Smart $]

The Bonding Jumper Main is sometimes the bolt that connects to the frame leaving the factory installed buss to be used by both conductors. Generally a single conductor for GC is limited to the connection point -- If you installed a EGC kit attached to the metal frame you would not attach a GC to it only EGC.

I understand the rationale, but as I stated, it is technically a violation. It also reflects the disposition of the installer as being too cheap, lazy, unprepared, etc. to install an EGC bus terminal bar. Even when manufactures do not include one with the panelboard, the enclosure usually has pre-punched holes for adding one or more as a listed accessory.

 

[mwm1752]

250.24(4) refrences an example in which the GEC can connect to an EGC buss by use of a bonding jumper only. 250.24(5) stipulates no load side connection to metal enclosures or EGC allowed to the grounded conductor. This occurs outside of the enclosure due to obvious connection within the the line side fed enclosure. There cannot be a parrallel current path at any point inside the enclosure. Panels that have a common grounding buss include specifications for grounded conductor and EGC connections to that same buss. ECG can also be an enclosure that is bonded per definitions. The bonded conductor is not mandated as the an only single connection just a minimum size.

 

[augie47]

On a service panel I see no reason other than aesthetics that you have a bar dedicated to grounding connections. Some smaller panels have only one bar that can be used for grounded and grounding terminations. Some panels have more than one bar connected by some type factory jumper. I have seen a few switchboards with terminal strips identified as "grounding conductors only"*.
As others point, if your ground return path relies on the can or the main bonding jumper then it is for grounding conductors only.

 

[trojans4]

Most residential 100A and 200A panels have only one terminal buss bar which contains a bonding screw to be used if the panel is the main service panel. The neutrals would be landed on this bar. Given that, it seems to me you would need to purchase a separate terminal bar for the EGC's. Maybe I haven't looked hard enough but I don't recall seeing any instructions saying how both neutrals and grounds can be landed on the single bar that come with the panel.