remaining amps

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sryan

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i have a 400A 480v panel that i am running some machinery off of. currently i have a total of 168,482VA total from the nameplates, 64,000 VA is the biggest load.
max demand = 168.482x1.25=210,602.5
210,602/(1.732×480)=253.3A
253.3x1.25=316.6A
400A-316.6=83.4A ampacity remaining
83.4/1.25=66.72A demmand remaining
66.72/1.25=53.376A rated remaining
does this look right? i can still put about 54A of load on my panel? let me know your thoughts and what area of code I should look at, thanks for the help
 
sryan said:
i have a 400A 480v panel that i am running some machinery off of. currently i have a total of 168,482VA total from the nameplates, 64,000 VA is the biggest load.
max demand = 168.482x1.25=210,602.5
210,602/(1.732×480)=253.3A
253.3x1.25=316.6A
400A-316.6=83.4A ampacity remaining
83.4/1.25=66.72A demmand remaining
66.72/1.25=53.376A rated remaining
does this look right? i can still put about 54A of load on my panel? let me know your thoughts and what area of code I should look at, thanks for the help
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Are these motor loads? IIRC, you should use 125% of the largest load but only 100% of the remaining loads. I think you have more room than 54 amps.
 
As far as the conductor ampacity, I agree with gadfly (above) in that you only need to apply the 1.25 fort the largest motor load, however, in regard to your 400 amp panel, you list the largest load as 64kva. Assuming this is a motor, approximately 60HP, you may already have a problem with a 400 amp panel IF the motor is across-the-line start (vs a drive). More details are needed in regard to the size/type load. In addition, load diversity will play a major role. Will all loads be on at the same time >?
 
these are all motor loads for some CNC maxhinery that are all not on at the same time, fed from a 277/480V 3 phase 4 wire system. the panel has a 400A main breaker. i am trying to see my remaining load available to add AC units to the building
 
sryan said:
the biggest load is 77A, with the other loads at 4.5, 60 and 60A.
(77×1.25)+4.5+60+60=220.75A
Click to expand...
What size and type is the panel feeder conductor, and what is its supply ocpd rating?

Supplying motor loads the 400A panel rating can be misleading. The feeder conductor must support 400A of calculated load to look at it the way you are (to a degree). You do not want to create a situation where two or more motors cannot start simultaneously, such as after a power outage.
 
FWIW CNC's will only see that max kW on spindle start. Heaviest load while running is large bore tapping, this at about 1/3 max kW. In my experience you have room to play.
 
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