Circuit Breakers controlling large motors

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GOZ

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Is it acceptable to use a Circuit Breaker to directly start and stop large motors?

I can not see anything in the NEC to forbid this but it seems to be poor practice IMO. Anyone know of an artical that mentions this? I am awear of 240.83(D) but nothing that is motor specific.

Thanks in advance.
 
GOZ said:
Is it acceptable to use a Circuit Breaker to directly start and stop large motors?

I can not see anything in the NEC to forbid this but it seems to be poor practice IMO. Anyone know of an artical that mentions this? I am awear of 240.83(D) but nothing that is motor specific.

Thanks in advance.
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The breaker can handle it depending upon the number pof times the nmotor is to be shut on and off. There are UL489 test requirements that dictate what the minimum life of a breaker is to be. Since "large motor" is somewhat ambiguous it is difficult to determine what the life of the breaker would be.
But, you have also avoided stating if this is 1ph or 3ph and if motor overload protection has been provided as thermal magnetic breaker are not intended to protect motors from overload.
 
templdl said:
The breaker can handle it depending upon the number pof times the nmotor is to be shut on and off. There are UL489 test requirements that dictate what the minimum life of a breaker is to be. Since "large motor" is somewhat ambiguous it is difficult to determine what the life of the breaker would be.
But, you have also avoided stating if this is 1ph or 3ph and if motor overload protection has been provided as thermal magnetic breaker are not intended to protect motors from overload.
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A little background to my question. I am reviewing a new elecrtical procedure that is going to be rolled out at my facility. In the description section of the procedure is the following.

1.1. Circuit Breaker:A power interrupting device that is capable of opening under not only a normal current load, but under the higher than normal currents associated with an electrical ?fault?. Sometimes used to directly start and stop large motors

I wanted to get clarification and full understanding before i give it my approval and i was not sure about the CB being used to directly start and stop motors.
 
GOZ said:
A little background to my question. I am reviewing a new elecrtical procedure that is going to be rolled out at my facility. In the description section of the procedure is the following.

1.1. Circuit Breaker:A power interrupting device that is capable of opening under not only a normal current load, but under the higher than normal currents associated with an electrical ?fault?. Sometimes used to directly start and stop large motors

I wanted to get clarification and full understanding before i give it my approval and i was not sure about the CB being used to directly start and stop motors.
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I would be glad to try to address you question but you still haven't answered mine.
 
Perhaps im asking the wrong question.

Does the Proposed definition seem to be factual and a correct?

1.1. Circuit Breaker:A power interrupting device that is capable of opening under not only a normal current load, but under the higher than normal currents associated with an electrical ?fault?. Sometimes used to directly start and stop large motors

 
templdl said:
I would be glad to try to address you question but you still haven't answered mine.
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I would give you the information stated if it were a physical application of such at my facility. All i have is the limited information submitted above. Through my expierience i have never seen or made such an installation for reasons that you had stated above aswell.
 
GOZ said:
Perhaps im asking the wrong question.

Does the Proposed definition seem to be factual and a correct?

1.1. Circuit Breaker:A power interrupting device that is capable of opening under not only a normal current load, but under the higher than normal currents associated with an electrical ?fault?. Sometimes used to directly start and stop large motors
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Typically a circuit breaker is primarily a protection device. Wikipedia says "A circuit breaker is an automatically operated electrical switch designed to protect an electrical circuit from damage caused by overload or short circuit. Its basic function is to detect a fault condition and interrupt current flow."

But, a switch or manual motor starter "breaks a circuit" by human operation as well. Without knowing your audience, it is hard to find much fault, but IMO your definition is not as good as Wikipedia's.
 
GOZ said:
Perhaps im asking the wrong question.



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In the countless specification that I have have to review over the years I have never rn across a spec such as this. If I were to interpret what is being required is that the device be capable of being opened ""manually" under normal current and higher than normal current.. But just what does higher than normal current mean, locked rotor current?
A common thermal magnetic circuit breaker would include short circuit protection set to trip automatically or interupt/clear a fault current of 10x the rating of the device up to its kaic rating.

But when you do address this spec always include a statement to the affect that it is per your interpretation of the specification. And you may want define how you interpreted it.
I hope that this is closer to what you are looking for. Otherwise we'll take another shot of it.
 
GeorgeB said:
Typically a circuit breaker is primarily a protection device. Wikipedia says "A circuit breaker is an automatically operated electrical switch designed to protect an electrical circuit from damage caused by overload or short circuit. Its basic function is to detect a fault condition and interrupt current flow."

But, a switch or manual motor starter "breaks a circuit" by human operation as well. Without knowing your audience, it is hard to find much fault, but IMO your definition is not as good as Wikipedia's.
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Thank you sir, I couldnt agree more. I actually opted to have them change the definition and referenced the definition NEC gives.
 
templdl said:
In the countless specification that I have have to review over the years I have never rn across a spec such as this. If I were to interpret what is being required is that the device be capable of being opened ""manually" under normal current and higher than normal current.. But just what does higher than normal current mean, locked rotor current?
A common thermal magnetic circuit breaker would include short circuit protection set to trip automatically or interupt/clear a fault current of 10x the rating of the device up to its kaic rating.

But when you do address this spec always include a statement to the affect that it is per your interpretation of the specification. And you may want define how you interpreted it.
I hope that this is closer to what you are looking for. Otherwise we'll take another shot of it.
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This is actually perfect. Thank you
 
GOZ said:
Perhaps im asking the wrong question.

Does the Proposed definition seem to be factual and a correct?

1.1. Circuit Breaker:A power interrupting device that is capable of opening under not only a normal current load, but under the higher than normal currents associated with an electrical ?fault?. Sometimes used to directly start and stop large motors
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I would remove the last sentence.
 
Whatever the code might say in my opinion using a CB as a motor control is not a good practice. I would advise my company to do the job right.
 
There is nothing wrong with using a breaker as a motor controler. It is just not what you are used too.




430.84(A)(2) Circuit Breaker. A branch-circuit inverse time circuit breaker rated in amperes shall be permitted as a controller for all motors. Where this circuit breaker is also used for overload protection, it shall conform to the appropriate provisions of this article governing overload protection.
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Thus far it appears as though we are shooting at shadows again. Does anybody know what "large motor" means, if the motor has overload protection and were it is located, an if this is a 1ph or 3ph application?
 
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