overcurrent protection

[thorn949]

have a motor rated at 15hp at 480v,using a combo starter with overload protection.starter is my disconnect also since it has fuse clips rated for 30amps.why would i need a stop/start for? starter is readily accessible and has a reset button on the outside.starter complies with art.430.103,430.74 and430.102b?? overkill??

 

[augie47]

you will probably get a far better engineered answer, but from a practical standpoint, I'd say you will get considerably greater life from the starter using the "contactor" as the load make/break means as you would using the "disconnect" if you plan totuen the load off wih any regularity.
Secondly, in the event of a power interuption, you might not want the motor to instantly start on power restoration.

 

[SEO]

you will probably get a far better engineered answer, but from a practical standpoint, I'd say you will get considerably greater life from the starter using the "contactor" as the load make/break means as you would using the "disconnect" if you plan totuen the load off wih any regularity.
Secondly, in the event of a power interuption, you might not want the motor to instantly start on power restoration.

I agree with augie47 I think that the motor starting automatically after a power interuption could be very dangerous in some situations.

 

[acrwc10]

I agree with augie47 I think that the motor starting automatically after a power interruption could be very dangerous in some situations.

If there are multiple motors that were connected like this the inrush of all of them starting at once,after a power outage, could cause a main to open. Unlikely scenario but possible.

 

[John Valdes]

A combination starter has a disconnect and a starter built into one enclosure. They are prewired for start stop buttons or switches. Why would you want to defeat the purpose of the device?