800 AMP Panelboard Service

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wattup

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We are running an 800 amp service from an 800 amp switch in outdoor switchgear to an 800 amp panel inside that has an 800 amp main breaker protecting it.
For sizing the conductors to feed this panel which has provisions for future circuits as well as the known loads to the max the panelboard is rated for are we within
code using (2) 500 MCM THHN conductors which are good for 760 amp total on 75* C scale for terminations. OR do I need to go up to the 600 MCM Rated 840 total?
Reason I asked is the rule that no panelboard should be loaded past 80% of its OCPD protecting it which would be 640 amps.
Their is only 400 amp load connected now but provisions for future.
 
If your calculated load is 760 amps or less then you can use the two sets of 500 kcmil via the next size up rule. IMO if you want to provide the additional 40 amps for the future then go with the 600's.
 
The rule in the NEC that confuses everyone is the continuous load. If everything in the panel is a continuous load then you could not load the breaker at 100% but rather to 80% unless you have a breaker that is rated 100% continuous load. If you have a combination of continuous and non continuous loads then you can load the overcurrent protective device to 100%.
 
infinity said:
If your calculated load is 760 amps or less then you can use the two sets of 500 kcmil via the next size up rule. IMO if you want to provide the additional 40 amps for the future then go with the 600's.
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