The Abbreviations are as follows:
[*] RLA = Running Load Amperes - same as Full Load Amperes, but more direct per HVAC and Motors,
[*] MCA = Minimum Circuit Ampacity - RLA with adjustments made to address the Circuit's Design Value ... If that makes any sense...
[*] LRA = Locked Rotor Amperes - Relates to the "Inrush" during Starting of Motors, normally used to classify Fuse types, Transformer and Circuit Breaker Design types, Circuitry specs, and lastly to add with Fault Calcs.
As to the Client's install Specs - with the Four 4" Ducts:
[*] The Four 350 MCMs per Duct is correct, figuring there will be 4 to 6 Current Carrying Conductors per Raceway.
350 THHN cu from the 90 degree column = 350 Amperes. 80 Percent of 350 equals 280 Amperes, so it's a little shy of 300 Amperes for each Raceway.
[*] 350 MCM under the 75 Degree column equals out to 310 Amperes, so even if the Parallel Feeders are just using the 3 Ungrounded Conductors and no Common Grounded Conductor "AKA Neutral" is used, the Feeders are still compliant.
[*] Minimum Equipment Grounding Conductor size for Circuits with an OCPD not exceeding 1200 Amperes is 3/0 cu, so the 3/0 will comply - as long as it's Copper, or "cu".
[*] Each Raceway will need a full size EGC, so its one 3/0 per Parallel Feeder Raceway, or Conduit.
Not a bad idea to include the Grounded Conductor to an Aux. or Remote Gear Section.
If this installation is for Service Equipment from a Utility Owned Transformer, or such, then the System's Grounded Conductor definitely needs to be brought to the Service Equipment and Bonded to the Enclosure(s) plus the Grounding Electrode System at the Building. This is how the Fault Path is provided back to the System's Origin (Transformers) when a Ground Fault occurs.
Also if this will be for Service Equipment, the PoCo may not even use the EGCs, as they are not of use.
So from all this, it's My opinion that the Client's Proposed installations will be to NEC Minimums.
A little more information would be helpful.
Edited tu fikx baad sphellieng
[This message has been edited by Scott35 (edited 10-04-2004).]