Todd Smith
Member
- Location
- Charleston, SC
Need to confirm maximum size system bonding jumper in a transformer with (12) sets of (4) 750 MCM CU feeders on the secondary side?
Maximum size of System Bonding Jumper in Transformer Derived System
- Thread starter Todd Smith
- Start date
- Status
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
Table 250.102(C)(1) is the table you need to size the bonding jumper. Is this what you need
- Location
- New Jersey
- Occupation
- Journeyman Electrician
There is no maximum size but there is a minimum. You would take size of the ungrounded conductor times the number of sets and then multiply by 12.5%.
12*750 kcmil=9000 kcmil*12.5%=1125 kcmil
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
Trying to wrap my head around 12 sets of 4, or did you mean 4 sets of 12?
Three phase four wire can have 4 sets of 12.
12 sets of four= 12 phase system??
Three phase four wire can have 4 sets of 12.
12 sets of four= 12 phase system??
:thumbsup:
- Location
- New Jersey
- Occupation
- Journeyman Electrician
12 sets of 4 conductors in each set. A,B,C,N
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
so 12 elements in parallel and 4 effective conductors.
Guess that is what I was thinking, but for some reason it just didn't sound right.
12 x 750 kcmil, just a little bit of current that can flow here.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
Yes so in this case (unless there is some adjustment factor) you end up with a 5700 amp set of secondary conductors.
Todd Smith
Member
- Location
- Charleston, SC
Yes - 12 sets of 750 MCM Cu A,B,C,N - 12 sets in parallel
Yes - 12 sets of 750 MCM Cu A,B,C,N - 12 sets in parallel
Reply - Wasn't there a past code that indicated 3/0 was the maximum?
Yes - 12 sets of 750 MCM Cu A,B,C,N - 12 sets in parallel
Reply - Wasn't there a past code that indicated 3/0 was the maximum?
- Location
- New Jersey
- Occupation
- Journeyman Electrician
No, although the table 250.102(C) is relatively new the old section 250.28(D) had the same requirements for 12.5% in the 2005 NEC. #3/0 is still the largest required GEC.
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