System Bonding Jumper at Step Down XFMR

[Fishn sparky]

Good morning team, lets get the morning started with an easy one!
Dumb question,
When bonding the neutral conductor to the GEC in a panelboard downstream of a step down xfmr ILO providing the bonding inside the xfmr, is the system bonding jumper still sized per 250.102, largest ungrounded phase conductor?

 

[xformer]

IMHO... See the Title of Table 250.102 (C) (1).

 

[infinity]

Yes T250.102(C)(1) is where you'll find the correct size for a SBJ. If the secondary condcutors are larger than 1100kcmil then you calculate the SBJ by multiplying the secondary conductor size by 12.5%. The same table is used for sizing the SSBJ between the transformer and the panel. You're drawing is incorrectly labeled, the arrow is not pointing to the SBJ.

 

[Fishn sparky]

Appreciate the responses.
Infinity, if my arrow is not pointing to the SBJ, what is it pointing to? I don't think it is an EGC nor GEC.

 

[infinity]

Appreciate the responses.
Infinity, if my arrow is not pointing to the SBJ, what is it pointing to? I don't think it is an EGC nor GEC.

It's the SSBJ supply side bonding jumper.

 

[Fishn sparky]

Thank you Infinity and all who answered.

Considered closed.

 

[don_resqcapt19]

In most cases the GEC has to go to an actual electrode and not to the "main or nearest ground bar".

 

[marcosgue]

In too many cases that I've seen the main GEC coming from the grounding electrode system (rods,cee, etc) to the main ground bar and from the main ground bar splits the GEC to separate derived system X0 point as many step down xfmr the premises have.