Cable tap rule using spliced cable

[philly]

I was wondering if a particular proposed installation would be code compliant.

An 800A breaker from an upstream panel is feeding a set of parallel 3/0 cables. Along the feeder these parallel 3/0 cables are spliced into (4) sets of 3/0 cables which eventually terminate into a 400A main breaker in the downstream panel. I'm not sure of the exact lenghts but am pretty sure both setctions of the feeder cable are greater than 50 ft or so.

I know the (4) sets of 3/0 cables are considered protected by the upstream 800A breaker but was curious if any of the provisions of 240.21 could be applied in order to consider the section of cable with only (2) sets of 3/0 adequately protected?

 

[Strathead]

I was wondering if a particular proposed installation would be code compliant.

An 800A breaker from an upstream panel is feeding a set of parallel 3/0 cables. Along the feeder these parallel 3/0 cables are spliced into (4) sets of 3/0 cables which eventually terminate into a 400A main breaker in the downstream panel. I'm not sure of the exact lenghts but am pretty sure both setctions of the feeder cable are greater than 50 ft or so.

I know the (4) sets of 3/0 cables are considered protected by the upstream 800A breaker but was curious if any of the provisions of 240.21 could be applied in order to consider the section of cable with only (2) sets of 3/0 adequately protected?

Actually, if understand your question correctly, the 4 sets of 3/0 are NOT protected by the upstream breaker. If they don't terminate in the same location on the load end, they are not parallel conductors, they are tap conductors and as such subject to the 25 foot or 10 foot restrictions of taps. If each phase, for example, terminated in a 10 hole polaris lug and 6 3/0's were also terminated in the same polaris, then distributed to 200 amp panels, they would be legal (when subjected to the tap rules)

 

[philly]

Actually, if understand your question correctly, the 4 sets of 3/0 are NOT protected by the upstream breaker. If they don't terminate in the same location on the load end, they are not parallel conductors, they are tap conductors and as such subject to the 25 foot or 10 foot restrictions of taps. If each phase, for example, terminated in a 10 hole polaris lug and 6 3/0's were also terminated in the same polaris, then distributed to 200 amp panels, they would be legal (when subjected to the tap rules)

It may be confusing how I worded the application. The 4 sets of 3/0 conductors do terminate into the same main breaker in the downstream panel. So the upstream feeder breaker had 2 sets terminated in the feeder breaker and then these 2 sets are spliced to 4 sets which then all terminate in the same main breaker downstream.

 

[Strathead]

It may be confusing how I worded the application. The 4 sets of 3/0 conductors do terminate into the same main breaker in the downstream panel. So the upstream feeder breaker had 2 sets terminated in the feeder breaker and then these 2 sets are spliced to 4 sets which then all terminate in the same main breaker downstream.

even more confused! Perhaps if you attach a one line diagram. The last thing you described now sounds like 2 sets of 3/0 leaving an 800 a breaker.

 

[Jljohnson]

even more confused! Perhaps if you attach a one line diagram. The last thing you described now sounds like 2 sets of 3/0 leaving an 800 a breaker.

That is how I read the OP as well, 2 sets of 3/0 leaving an 800A breaker. That in itself is not in compliance w/ NEC as described.