I have a customer that we are designing a control panel for that contains a PLC, power supplies and several motor starters. The customer would like us to size the OCPD located inside of the control panel using the sum of the full load currents of all motors and apparatus including 2 future motors that may be installed in about 8 months after the initial installation. From what I can tell from reading NEC article 409.21, I can not include future loads in my OCPD calculation. Is this correct?
OCPD for Control Panels
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bdarnell
Senior Member
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- Indianapolis, IN
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- Retired Engineer
Re: OCPD for Control Panels
I don't read it that way. 409.21 (new section in 2005 for those looking for it in 2002) refers to the overcurrent device for the circuit supplying the control panel. I don't read it to mean any overcurrent device inside the panel for panel components or motors that it might control.
Someone else that has researched this article more in depth might have a different take on it.
I don't read it that way. 409.21 (new section in 2005 for those looking for it in 2002) refers to the overcurrent device for the circuit supplying the control panel. I don't read it to mean any overcurrent device inside the panel for panel components or motors that it might control.
Someone else that has researched this article more in depth might have a different take on it.
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- PE (Retired) - Power Systems
Re: OCPD for Control Panels
409.21(C) says to include "all other motors...that could be in operation at the same time."
Personnaly, I do not see this section as preventing you from including future loads.
But this section is really for the feeder circuit to the panel so if there is an upstream OCPD,per 409.21(B)(1), then the internal panel device can be sized differently.
409.21(C) says to include "all other motors...that could be in operation at the same time."
Personnaly, I do not see this section as preventing you from including future loads.
But this section is really for the feeder circuit to the panel so if there is an upstream OCPD,per 409.21(B)(1), then the internal panel device can be sized differently.
Re: OCPD for Control Panels
Depends upon the purpose of this OCPD. What is it protecting? Are all the loads that are being feed individually protected? (That protection can't be supplimentary protectors either.) If so then your only focus should be on the protection of conductors from the OCPD and the OCPD for the individual loads. As such you could size if for additional loads.
Depends upon the purpose of this OCPD. What is it protecting? Are all the loads that are being feed individually protected? (That protection can't be supplimentary protectors either.) If so then your only focus should be on the protection of conductors from the OCPD and the OCPD for the individual loads. As such you could size if for additional loads.
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