How to determine the kVA of a panel given the Amps per phase

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charlie b said:
I am not sure where you are going with this. If you are getting current values from an electrician, then obviously the panel is built, it has a feeder coming in to it, and there is a feeder breaker at the other end of that wire. So the design process is long since completed. What, then, is your role?

If you are starting with a new design project, and if you are given a set of loads (in units of amps), some single phase 120, some single phase 208, and some three phase 208, then what you do is,
  • Add up all the single phase 120 current values, and mutiply the sum by 120,
  • Add up all the single phase 208 current values, and mutiply the sum by 208,
  • Add up all the three phase 208 current values, and multiply the sum by 208, and then multiply that result by 1.732,
  • Add up the three values calculated above,
  • Divide that sum by 208, and divide again by 1.732.
  • You now have a design value for the current that will be drawn on each of the three phases (assuming you can balance the loads closely enough). That is the value you use as a design basis for selecting the panel rating, the feeder to the panel, and the feeder breaker from the upstream panel. Be sure to add some margin for future load growth. Most of my clients have asked for 20% above the calculated load.
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Trying to verify kva load on pnlbd when you say add up current values would that be individual breaker values in the panel?
 
I was provided the following information for a 208/120V 3ph 4W Panel,

Phase A: 6.5
Phase B: 7.8
Phace C: 13.6
Neutral : 7A
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Sounds like someone went out and measured it. Do you know for sure that all the loads were on at the time and drawing their maximum current?

Probably would be best to take a close look at what loads are actually on the panel and size the UPS to the worst case of the loads that might be on at the same time rather than relying on a measured value.
 
Since this thread is 6 years old it would probably be best if a new thread was created if someone wants to start one

Roger
 
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