How do I determine the size of a new circuit?

Thread Starter


Joined Jan 4, 2007
I'm adding some equipt. in my data center. To determine the number of circuits that I will need, do I just add up the amps input on each device? For example, if my equipt. lists 1.1, 1.3, 3.5, 5.5, 5.5, 3.1, then I would need one 20 amp circuit? And if it adds up to more, than I would need to add another circuit?


Joined Nov 1, 2006
That's nearly correct; however, to avoid nuisance tripping you can't exceed 80% of a circuit breaker's or fuse's ampacity. Ditto for wiring to heep heat down. If that isn't enough to supply all your equipment then you need to add another circuit. Also, try to add new 120 V circuits so the total current on each side of the 240 V incoming lines or mains is approximately equal or balanced.