Feeder Sizing - Continuous/Noncontinuous

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darren71

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I have an application where I'm feeding a panel, which is to power (10) Roof Top Units (RTU's) with three-stage electric heaters in them. The electric heat is the biggest load in each, and the Min. Circuit Amps (MCA) of each RTU is sized for 100% of the heater load, plus 125% of the largest motor, followed by 100% of the sum of the remaining motors. The OCPD for each RTU is then sized the next standard size over the MCA. If the MCA of each RTU is 91 Amps and the OCPD is 100A, what should the feeder size be to the panel feeding the RTU's? My basic question is, do I figure the RTU's as continuous (10 x 91 x 1.25) or non-continuous (10 x 91 x 1.00) for sizing my panel feeder? Is there an article that clearly deals with this? I have found articles that deal with this area, but I'm not sure how to treat multiple RTU's. Another option would be to take 125% of the largest and the remainder at 100%? PS: Don't get too caught up in the numbers, I made them up to make the application easier. It is based on a real design I have, though. Thanks!
 
Re: Feeder Sizing - Continuous/Noncontinuous

So I can't assume the MCA of the RTU's is already 125% of the load and simply add them up and automatically have the correct feeder size for the panel? Thanks for the reply, by the way, it does help me understand this more.
 
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