When sizing a breaker or fuse for motors using table 430.52 you adjust using the corresponding percentages for your type of fuse or breaker. So let's just say I'm using 250% column. 430.110 also says disconnecting means not less than 115% for motors. So would I size my disconnect at 250% since it says " not less than 115%"? If not why and what should I go off of?
Motor disconnect size
- Thread starter OkieSpark
- Start date
- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
You size the fuses for the motor, then the disconnect must match the fuse size. So a fused disconnect with properly sized fuses will by default always exceed the 115% requirement. The reason the 115% rule exists is for when you have the disconnect DOWNSTREAM of the
motor branch-circuit short-circuit and ground-fault protective device, i.e. the local disconnect "within sight" of the motor.
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motor branch-circuit short-circuit and ground-fault protective device, i.e. the local disconnect "within sight" of the motor.
.
- Location
- Illinois
- Occupation
- retired electrician
If the disconnect is only the motor disconnect, it does not have to have a rating greater than 115% of the motor FLA .
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Don is there a code article?