Another 430.109 Question

[xguard]

"430.109 Type.
The disconnecting means shall be a type specified in 430.109(A), unless otherwise permitted in 430.109(B) through (G), under the conditions specified." [2014 NEC]

A molded case circuit breaker falls under one of the "shall be" types.

A branch-circuit over current device falls under one of the "unless otherwise permitted...under the conditions specified" types. (for motors 1/8 hp or less)

My question: If my branch-circuit over current device is a molded case circuit breaker (in a breaker panel) am I permitted to use it as the motor disconnecting means for motors larger than 1/8 hp?

I'm very confused by this section, maybe I have a screw loose, I appreciate most any responses.

 

[Jraef]

"430.109 Type.
The disconnecting means shall be a type specified in 430.109(A), unless otherwise permitted in 430.109(B) through (G), under the conditions specified." [2014 NEC]

A molded case circuit breaker falls under one of the "shall be" types.

A branch-circuit over current device falls under one of the "unless otherwise permitted...under the conditions specified" types. (for motors 1/8 hp or less)

My question: If my branch-circuit over current device is a molded case circuit breaker (in a breaker panel) am I permitted to use it as the motor disconnecting means for motors larger than 1/8 hp?

I'm very confused by this section, maybe I have a screw loose, I appreciate most any responses.

Maybe. As per usual with the NEC, you can't jump right to a section like 430.109 until you have already gone through the BEGINNING of that section. In this case it starts at 430.101, but really .102 is the meat of it.

To use a BCP device that is in a remote breaker panel as the required disconnect for the motor, it would first off have to be lockable (which can be done with an accessory in most cases), but also you would have to meet the requirements laid out in 430.102 (B)(1) or (2) exceptions (a) or (b). If neither of those apply to your situation, then the answer would be no and you will need a disconnecting device either at the motor or at the controller.

 

[Dale001289]

"430.109 Type.
The disconnecting means shall be a type specified in 430.109(A), unless otherwise permitted in 430.109(B) through (G), under the conditions specified." [2014 NEC]

A molded case circuit breaker falls under one of the "shall be" types.

A branch-circuit over current device falls under one of the "unless otherwise permitted...under the conditions specified" types. (for motors 1/8 hp or less)

My question: If my branch-circuit over current device is a molded case circuit breaker (in a breaker panel) am I permitted to use it as the motor disconnecting means for motors larger than 1/8 hp?

I'm very confused by this section, maybe I have a screw loose, I appreciate most any responses.

430.109(A)(B) address disconnecting means - you still need a controller and overloads - sometimes can be contained within the same unit. For example over 1HP, look at 430.32.

 

[xguard]

For example:

I have a magnetic motor starter in a box next to a 5 hp motor. The breaker panel is less than 50 feet away and visible. Is it permissible to use the branch circuit breaker in the panel as the motor (and controller) disconnect?

My intention with this example is to constrain the point to the branch circuit breaker being used as the disconnect for a motor greater than 1/8 hp. I don't see where anything in 430.102 prohibits this.

 

[jap]

For example:

I have a magnetic motor starter in a box next to a 5 hp motor. The breaker panel is less than 50 feet away and visible. Is it permissible to use the branch circuit breaker in the panel as the motor (and controller) disconnect?

My intention with this example is to constrain the point to the branch circuit breaker being used as the disconnect for a motor greater than 1/8 hp. I don't see where anything in 430.102 prohibits this.

Yes, a circuit breaker can be used as a motor disconnecting means.

JAP>

 

[Dale001289]

For example:

I have a magnetic motor starter in a box next to a 5 hp motor. The breaker panel is less than 50 feet away and visible. Is it permissible to use the branch circuit breaker in the panel as the motor (and controller) disconnect?

My intention with this example is to constrain the point to the branch circuit breaker being used as the disconnect for a motor greater than 1/8 hp. I don't see where anything in 430.102 prohibits this.

Yes it can be your disconnect but FYI the starter is your controller. The CB doesn’t have to be within sight of the motor if it is lockable in the open position. Make sure you have overload protection. The CB has to withstand locked rotor current, so unless it’s magnetic only, you might trip.


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[augie47]

Yes it can be your disconnect but FYI the starter is your controller. The CB doesn’t have to be within sight of the motor if it is lockable in the open position. Make sure you have overload protection. The CB has to withstand locked rotor current, so unless it’s magnetic only, you might trip.


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To avoid confusion to the casual reader note that the provision for an out of sight lockable disconnect only applies where some specific conditions listed in 430.102 are in place.

 

[jap]

The CB has to withstand locked rotor current

Where does it say in the code book that a Circuit Breaker feeding a motor load "has to withstand the locked rotor current" ?


JAP>

 

[Dale001289]

Where does it say in the code book that a Circuit Breaker feeding a motor load "has to withstand the locked rotor current" ?


JAP>

This is not a requirement-just pointing out a thermal magnetic inverse time CB might have nuisance trips.


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[Dale001289]

To avoid confusion to the casual reader note that the provision for an out of sight lockable disconnect only applies where some specific conditions listed in 430.102 are in place.

True. It appears he’s got the main rule covered - Disc within sight of the controller.


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[kwired]

This is not a requirement-just pointing out a thermal magnetic inverse time CB might have nuisance trips.


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I seldom have trouble with them. When I do, the motor is usually experiencing troubles as well.

Seen many 10 HP 480 volt motors start without tripping 15 amp I-line, FA type breaker. NEC allows this to be a 35 amp breaker.

Also seen motors driving moderately high inertial loads that do need most of that 250% or it will trip before it reaches full speed.

 

[Dale001289]

I seldom have trouble with them. When I do, the motor is usually experiencing troubles as well.

Seen many 10 HP 480 volt motors start without tripping 15 amp I-line, FA type breaker. NEC allows this to be a 35 amp breaker.

Also seen motors driving moderately high inertial loads that do need most of that 250% or it will trip before it reaches full speed.

A mag only instantaneous CB is a better application for Motors since you only need short circuit protection and you don’t need the thermal aspect.


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[Dale001289]

For example:

I have a magnetic motor starter in a box next to a 5 hp motor. The breaker panel is less than 50 feet away and visible. Is it permissible to use the branch circuit breaker in the panel as the motor (and controller) disconnect?

My intention with this example is to constrain the point to the branch circuit breaker being used as the disconnect for a motor greater than 1/8 hp. I don't see where anything in 430.102 prohibits this.

Just curious as to how you intend to start/stop the motor. Are you planning to use the disconnect (CB) or add a local push-button control station to interface with the starter?


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[Dale001289]

I seldom have trouble with them. When I do, the motor is usually experiencing troubles as well.

Seen many 10 HP 480 volt motors start without tripping 15 amp I-line, FA type breaker. NEC allows this to be a 35 amp breaker.

Also seen motors driving moderately high inertial loads that do need most of that 250% or it will trip before it reaches full speed.

I think you meant "460 volt", not 480.

 

[augie47]

So many of the applications I see don't lend themselves to a Instantaneous Trip Motor Circuit Protector as they can only be used as part of a listed combination motor controller and it's often too late in the game for the electrician to address that,

 

[kwired]

A mag only instantaneous CB is a better application for Motors since you only need short circuit protection and you don’t need the thermal aspect.


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So many of the applications I see don't lend themselves to a Instantaneous Trip Motor Circuit Protector as they can only be used as part of a listed combination motor controller and it's often too late in the game for the electrician to address that,

Yes. They are great for MCC's or combination starters.

Majority of what I work on doesn't involve either.

Motor circuit originating from a panelboard - thermal mag breakers are typically your only option. Larger frame breakers do usually have adjustable mag trip setting though.

 

[jap]

I think you meant "460 volt", not 480.

He probably did mean 480.

Right or wrong, that's pretty common lingo for us common folks

Jap>

 

[kwired]

He probably did mean 480.

Right or wrong, that's pretty common lingo for us common folks

Jap>

I meant operating at 480 nominal. Most of them I see is a 460 volt rated motor, operating voltage is often 490 -500.

 

[jap]

I meant operating at 480 nominal. Most of them I see is a 460 volt rated motor, operating voltage is often 490 -500.

Most of us knew what you meant.

JAP>

 

[Dale001289]

I meant operating at 480 nominal. Most of them I see is a 460 volt rated motor, operating voltage is often 490 -500.

Correct, LV motors are rated (on the nameplate) as 460V, 230V and 115V - the operating (system) voltages are 480V, 240V and 120V respectively. This has 'evolved' over the years - if you go back far enough you'll find motor nameplates with 440V, 220V and 110V.