Determining "full-load current for each incoming supply circuit" NEC 409.110(2)

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crispy_copper

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Location
USA
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Electrical Engineer
For the markings required on industrial control panels, how do I determine the full load current for each incoming supply circuit? Is this done purely by looking at the incoming supply conductors and determining the current they can provide under normal conditions using a chart, or does it depend on the equipment in the cabinet itself and what method would be used in this case?

I saw plenty of posts about calculating the FLA of a cabinet, but the marking requirement asks for the full load current of the incoming supply circuit, is this different?
 
I assume they are asking the available fault current so the equipment SCCR can be sized accordingly.


(note: please update your profile to show your association with the industry other than"electrical" )
 
The available fault current is covered in 409.22. I am adding part of the text from 409.110 also for additional context.


409.22 Short-Circuit Current Rating
(A) Installation. An industrial control panel shall not be installed where the available fault current exceeds its short-circuit current rating as marked in accordance with 409.110(4).
(B) Documentation. If an industrial control panel is required to be marked with a short-circuit current rating in accordance with 409.110(4), the available fault current at the industrial control panel and the date the available fault current calculation was performed shall be documented and made available to those authorized to inspect, install, or maintain the installation.


409.110 Marking. An industrial control panel shall have permanent markings that are visible...
(1) Manufacturer's name, trademark...
(2) Supply voltage, number of phases, frequency, and full-load current for each incoming supply circuit.
(3) Where the industrial control panel is supplied by more than one electrical power source...
(4) Short-circuit current rating of the industrial control panel based on one of the following...
(5) If the industrial control panel is intended as service equipment...
(6) Electrical wiring diagram...
(7) An enclosure type number.
 
I'm familiar with those Sections. Apparently I don't understand your question.
 
For example, if a cabinet is powered by two copper 75 degree Celsius 350kcmil wires per phase, then based on ampacity table 310.16 would the full-load current for the incoming supply as it pertains to 409.110(2) be 310A+310A=620A?
 
You're misinterpreting.
The term "for each incoming supply circuit" means IF you had a panel with MORE THAN ONE supply circuit, then the data plate must show the data for each individual one. So lets say you had a control panel with a 480V 3 phase feed for motors, and a separate 240V single phase feed to power something else like an air conditioner. You have to show the data for each circuit individually, not just the larger one or a totalized version.
 
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