Feeder tap AL while feeder CU

[hhsting]

I have 1200A main service fused disconnect fused at 1200A feeding trough. The trough feeds two fused disconnects one 800A and second 100A with two electric utility meters

The feeder cable size from the service disco to trough is 6 sets of (3#500 kcmil, 1#30G).

The feeder is then tapped to one of the 800A disconnect from trough. The tapped conductor size is 3 sets of (4#500 AL, 1#2/0G)


Questions:

1. Can feeder be copper and tapped conductors be aluminum? NEC 2014 code allows it or not?

2. What size the tapped EHC be 3/0 CU or 250 kcmil AL?

3. Should not the feeder cable number from service disco to trough be 4#500 kcmil not 3#500kcmil? It’s after main service disco but before utility meters

 

[infinity]

Yes there can be aluminum conductors tapped to copper conductors with the proper connectors. The EGC for the tap needs to be sized according to the OCPD ahead of the feeder being tapped in this case 1200 amps. Why 6 sets of 500's for 1200 amps? Also the #3/0 EGC is too small according to 250.122(B).

 

[hhsting]

Yes there can be aluminum conductors tapped to copper conductors with the proper connectors. The EGC for the tap needs to be sized according to the OCPD ahead of the feeder being tapped in this case 1200 amps. Why 6 sets of 500's for 1200 amps? Also the #3/0 EGC is too small according to 250.122(B).

I don’t follow the 6 sets of 500 kcmil would be 380x6=2280A so how it’s small? Also Table 250.122 for 2000A overcurrent protection is 3/0awg?????


Sent from my iPhone using Tapatalk

 

[infinity]

I don’t follow the 6 sets of 500 kcmil would be 380x6=2280A so how it’s small? Also Table 250.122 for 2000A overcurrent protection is 3/0awg?????

I didn't say it was too small, I'm asking why you would need 6 sets when 4 sets (380*4=1520 amps) are more than enough ampacity. In T250.122: 1200 amps=#3/0 copper.

 

[augie47]

Agree, AL tap would be permitted... likely candidate would be a "Polaris" tap.