I'm sure this has been discussed many times, so forgive me for asking again:
Code requires for a motor that the MINIMUM conductor size is 125% of FLA. Then, code permits an OCPD to be sized at up to 250% of motor FLA.
Question: if the OCPD is upsized greater than 125% of motor FLA, does the code require the associated conductors to upsized accordingly? In Annex D, Example D8, they first describe conductor sizing, then OCPD rating. No where does it state that the conductor must be sized to the OCPD rating.
My example is a 60hp motor with FLA of 70A. There is a 150A circuit breaker ahead of the starter. Assuming 75C rating, can I use #3 wire, (100A rating), or do I have to use 1/0 awg, (150 A rating)?
I am concerned that the 100A wire would melt before the 150A breaker would trip. Is my concern legit? Where in the code is this explained?
Thanks all for your help.
Code requires for a motor that the MINIMUM conductor size is 125% of FLA. Then, code permits an OCPD to be sized at up to 250% of motor FLA.
Question: if the OCPD is upsized greater than 125% of motor FLA, does the code require the associated conductors to upsized accordingly? In Annex D, Example D8, they first describe conductor sizing, then OCPD rating. No where does it state that the conductor must be sized to the OCPD rating.
My example is a 60hp motor with FLA of 70A. There is a 150A circuit breaker ahead of the starter. Assuming 75C rating, can I use #3 wire, (100A rating), or do I have to use 1/0 awg, (150 A rating)?
I am concerned that the 100A wire would melt before the 150A breaker would trip. Is my concern legit? Where in the code is this explained?
Thanks all for your help.