Ocpd

P

pedro1200

Member
Location
Ny
Occupation
Electrician
In the nec a 500kcmil rated at 380 can be protected with a 400a ocpd ( next size up) how come you can’t protect a 21 amp rated conductor with a 20a ocpd for brach circuits
 
pedro1200 said:
Everything i’ve read states this.it was strange to me
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You can always protect a larger conductor with a smaller breaker. The breaker/OCPD just has to be equivalent, or less, to the conductor.

You might have to adjust the EGC due to the ungrounded conductors being increased in some cases.
 
pedro1200 said:
how come you can’t protect a 21 amp rated conductor with a 20a ocpd for brach circuits
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This is not the case, so you either stated something incorrectly, or are misunderstanding the issue.
If you have a LOAD that is rated to draw 21A, you cannot use a 20A rated conductors for that, and since the OCPD is protecting the conductors, putting a 20A OCPD would be indirectly wrong as well.
 
Jraef said:
This is not the case, so you either stated something incorrectly, or are misunderstanding the issue.
If you have a LOAD that is rated to draw 21A, you cannot use a 20A rated conductors for that, and since the OCPD is protecting the conductors, putting a 20A OCPD would be indirectly wrong as well.
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Im not talking about limiting the protection to 20a and talking about the conductor protection based on the conductors rating limitations…… good night
 
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