SBJ, SSBJ, MBJ

[Smart $]

I think what Smart is talking about is the verbiage found in 250.30(B) which is different than what it was in the 08 edition.

I have been referencing 250.30(A)(2), contrasting 250.30(A)(1) Exception No. 2... without fail.

And the 11 cycle says

But in the exception of (1) in the 11 cycle it clearly states
Which states that it is permissible as long as there is no parallel path, but (2) requires the installation of the SSBJ therefore not allowing the bonding at both ends. I think that the exception of (1) will trump (2) and the installation is allowed but who am I?

If the "shall be permitted" exception were to the "shall be" requirement, perhaps. However in this case, the exception is regarding a completely different requirement. The "shall be permitted" exception is to a requirement for installing a system bonding jumper, while the "shall be" requirement is regarding installation of a supply-side bonding jumper. Not the same thing.

 

[jwelectric]

I have been referencing 250.30(A)(2), contrasting 250.30(A)(1) Exception No. 2... without fail.



If the "shall be permitted" exception were to the "shall be" requirement, perhaps. However in this case, the exception is regarding a completely different requirement. The "shall be permitted" exception is to a requirement for installing a system bonding jumper, while the "shall be" requirement is regarding installation of a supply-side bonding jumper. Not the same thing.

Sorry I meant to put (2) not (B). I have been known for making many mistakes throughout my life.

I do agree that the text in (2) is a requirement that the EGC, EBC, SSBJ, depending on which code cycle one is looking at as to what to call this conductor, is to be installed and I have been misunderstanding the Section for almost three years now.

I wonder what the intent was of the Code Making Panel with Exception to (A)(1)

Thank you for setting me straight

 

[Smart $]

... I have been known for making many mistakes throughout my life.

Mistakes are inevitable in everyone's life.

I do agree that the text in (2) is a requirement that the EGC, EBC, SSBJ, depending on which code cycle one is looking at as to what to call this conductor, is to be installed and I have been misunderstanding the Section for almost three years now.

I wonder what the intent was of the Code Making Panel with Exception to (A)(1)

The exception has existed for many Code cycles, and many existing systems have been installed as such. It's only a conflict in 2011 NEC... probably overlooked when 250.30(A)(2) was changed.

Thank you for setting me straight

You're welcome...always glad to help :thumbsup:

 

[ajayl]

Thanks for the help.

 

[ajayl]

A main bonding jumper is installed at the first disconnect of a service. A system bonding jumper is installed at the source or the first disconnect, but not both, of a Separately Derived System. The issue of where the system bonding jumper is installed is strictly a design issue. There is no real reason to install it in one location or the other.

Thanks. This post helped my understand that the main bonding jumper deals with the service and the system bonding jumper deals with a separately derived system which clarified the subject. Also i now know i can use either method (bond the transformer case to xo or the first disconnect) but not both.

 

[ajayl]

But primary windings of the transformer have no electrical connection to the secondary windings and that is why it is called a separately derived system - it is a system that essentially is separate from the primary, and has no voltage reference to the primary (until we do ground a point of the secondary).

Thanks. And once we ground a point on the secondary there is a voltage reference? what is the reference between (to help me try to understand)?

 

[ActionDave]

Here's some clarification for the 2014 NEC:

Read that four times. Three times forwards, fourth time backwards.

It made the most sense the fourth time.

 

[kwired]

Thanks. And once we ground a point on the secondary there is a voltage reference? what is the reference between (to help me try to understand)?

If there is a grounding electrode - then the reference is to earth, as well as anything that has continuity to earth, and/or the grounding electrode system.

 

[MarineTech]

If you have a transformer and you connected your system bonding jumper (from XO to transformer case) and then connected a supply side bonding jumper (from transformer case to main panel) would you still use a main bonding jumper in the main panel? I don't think you would (grounding conductor would become a current caring conductor).
But this brings up another question which method would you use, the MBJ at main panel or SBJ, SSBJ? My hypothesis is the distance between transformer and main panel would determine the method.

So is the system bonding jumper and main bonding jumper are the same thing?

In regards to,

My hypothesis is the distance between transformer and main panel would determine the method.

For me, the people who do a lot of the Transformer Installs (Separately derived, earthed) will use the most effective (Cost and time) SBJ method which is usually equipment dependent.

 

[BPoindexter]

If you have a transformer and you connected your system bonding jumper (from XO to transformer case) and then connected a supply side bonding jumper (from transformer case to main panel) would you still use a main bonding jumper in the main panel? I don't think you would (grounding conductor would become a current caring conductor).

You are using the term main panel and main bonding jumper in a way that implies this is a service, however the graphic used and term SBJ apply to separately derived systems (SDS) not a service.

SSBJ is for bonding equipment on the supply side of a service (upstream of the disconnecting means) and again does not apply to a SDS.

 

[infinity]

SSBJ is for bonding equipment on the supply side of a service (upstream of the disconnecting means) and again does not apply to a SDS.

SSBJ refer to separately derived systems not services. {250.30(A)(2)}