Circuit Size

[Alwayslearningelec]

I'm referencing this mechanical schedule and a bit confused as to what the circuit size needs to be. There are different ampacities listed.

The electrical drawings are calling for one set of #500's in RGS. which is good for 380. Still under any of the ampacities listed below.

Ahhh...I see if I add 125% for continuous load it gets me to 482A. So one set of #500 is not correct.

 

[infinity]

The electrical drawings are calling for one set of #500's in RGS. which is good for 380.

The MCA is 482 amps so a 380 amp conductor will not work?

 

[don_resqcapt19]

Even for the full load amps, 500 kcmil is not acceptable. The full load is 385 amps and the ampacity of 500 kcmil is 380 amps. There is no round up rule here.

 

[Master Nater]

electrical drawing is wrong. it looks like 2x 250mcm cu or 2x 350mcm alum is what it needs.

 

[Alwayslearningelec]

They are calling for 2 sets #500..way oversized Imo

 

[infinity]

They are calling for 2 sets #500..way oversized Imo

Ah so it's two sets not one as mentioned in the OP. Yes two sets is overkill for 385 amp load unless your run is very long and voltage drop is an issue.

 

[steve66]

We can't see the entire schedule, but with 2 rows, does this chiller need 2 connections, each sized for 482 amps?

 

[david luchini]

Looks to me like the electrical engineer was given "800A circuit breaker" as the information to design by, rather than the MCA.

Therefore two sets of 500mcm.