Feed thru lugs

hhsting

Senior Member
Attached sketch shows xfmr feeding Panel R1-1 with 600kcmil phase conductors 400A main breker. Panel R1-1 is feed thru and feeds MLO 400A R1-2 via 600kcmil conductors. R1-2 has subfeed lugs which feed R1-3 with 200A main breaker via 600 kcmil conductors.

Question is would 600kcmil conductors between Panel R1-1 and R1-2, Panel R1-2 a d R1-3 be protected by 400A main breaker Panel R1-1 or it depends on total demand load between panels?
 

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kwired

Electron manager
Location
NE Nebraska
you have 400 amp protection on the feeders. You didn't state what size conductors supply the last panel, but everything is fine if they have an ampacity of 400 amps or even 351 amps for that matter. They also can have ampacity of 200 as long as lengths comply with feeder tap rules.
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
Panel R1-2 has subfeed to last panel R1-3.

The R1-3 is supplied by 4-600 kcmil + 1-3/0 Grd. R1-3 is 200A panel with main breaker of 200A.
Ah, so the conductors are all the same size, 600 kcmil. The 400 amp OCPD protects the 600's which are feed through at the second enclosure. The last panel has a 200 amp rating and a 200 amp main protected it. That 's all good. You could use a smaller SSBJ and EGC instead of the #3/0. The SSBJ minimum would be #1/0 and the EGC for 400 amps would be #3.
 

kwired

Electron manager
Location
NE Nebraska
Ah, so the conductors are all the same size, 600 kcmil. The 400 amp OCPD protects the 600's which are feed through at the second enclosure. The last panel has a 200 amp rating and a 200 amp main protected it. That 's all good. You could use a smaller SSBJ and EGC instead of the #3/0. The SSBJ minimum would be #1/0 and the EGC for 400 amps would be #3.
And as I said the last panel could be fed with 200 amp conductor - if length is short enough to comply with feeder tap rules
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
And as I said the last panel could be fed with 200 amp conductor - if length is short enough to comply with feeder tap rules
He didn't mention length but given the conductor size he would be limited to 25'.
 
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