I'm trying to settle an argument between myself and a colleague.
We are designing new product. It's 3 phase WYE rated at 343A/phase. (120/208Vac)
We disagree on the cable size needed in the field for installs.
We agree that we need a 450A breaker, but we disagree on the cable sizing.
8-104 (4) and (5)
Why do we have to derate the overcurrent device MORE with single conductor? With a 100% continuous rated breaker we can rate the circuit at 100 % with multiple conductors but only at 80% with single conductor.
Can anyone shed some light on why it would be lees when a single...
Say for example you are pulling feeders for a tap box to a meter stack in a condo style hi-rise and you are using parallel runs to get 3 phase 120/208 with 800 amps. It is protected by an 800 amp circuit breaker from the transformer. You've installed 3 x 3" pipes to pull 400...