Undersized Cable?

[harritr1]

I have come across some cables that I believe to be undersized but I wanted to see if maybe there is some weird industry rule/exception I am just unaware of.

So I have a 1200A automatic transfer switch upstream of 6 single conductor 750kcmil CU cables (2 per phase) in underground conduit with an 800A switch at the end. With my calculations I don't see how these cables are protected by the ATS since their ampacity does not go above 1200A.

Am I missing something here or is there something in the code about these cables not needing to be protected by the ATS?

Any comments or tips are helpful

 

[infinity]

I have never seen an ATS with overcurrent protection so I would assume that this ATS has none. The OCPD's ahead of the normal and EM feeders provides the protection for the 800 amp feeder to the disconnect.

 

[Jraef]

I have never seen an ATS with overcurrent protection so I would assume that this ATS has none. The OCPD's ahead of the normal and EM feeders provides the protection for the 800 amp feeder to the disconnect.

Correct. Just because the ATS is capable of 1200A doesn't mean the circuit is going to carry 1200A. There's nothing wrong with using a 1200A rated device on an 800A circuit.