motor rated breakers

[don_resqcapt19]

From the UL Guide Information for Combination Motor Controllers (NKJH)

This category covers combination motor controllers, which provide the motor branch-circuit functions of motor controller, disconnect means, short-circuit and ground-fault protection and motor overload protection. The functions may be provided by individual discrete components or be combined in a single controller unit.
These products are marked "Combination Motor Controller" to signify that all of the motor branch-circuit functions indicated above have been investigated and are included in the certification of the controller.
An open-type combination motor controller is intended for factory installation in a switchboard, motor control center, industrial control panel or the like, or for field installation in an enclosure for industrial control equipment, a cabinet or a cutout box.
Combination motor controllers are marked with a short-circuit rating and are intended for connection to circuits in which the available fault current does not exceed the marked short-circuit rating.

 

[iwire]

I would never call a panelboard a panel. its a panelboard.

But electrians do, and the OP is an electrian. That was why I said we just speak different languages.

 

[templdl]

But electrians do, and the OP is an electrian. That was why I said we just speak different languages.

From the UL Guide Information for Combination Motor Controllers (NKJH)

Would this include an MCP on the primary side of a VFD? You would be more inclined to see a TM UL 489 listed breaker there since it would be very doubtful for an MCP to protect a motor circuit on the secondary side of a VFD as a part of a combination motor starter.

 

[petersonra]

From the UL Guide Information for Combination Motor Controllers (NKJH)

which has little to do with MCPs as they are recognized as UL508 items I think. Or maybe they are 489 recognized. In any case, they are not listed at all.

 

[templdl]

which has little to do with MCPs as they are recognized as UL508 items I think. Or maybe they are 489 recognized. In any case, they are not listed at all.

The answer is 'B', UL 489 recognized.
The important thing to remember is that must rely on another device such as the OLR of a starter to protect the MCP from overcurrent as an MCP in completely stupid when it comes the currents that exceed its rating. The MCP can be destroyed.

 

[don_resqcapt19]

which has little to do with MCPs as they are recognized as UL508 items I think. Or maybe they are 489 recognized. In any case, they are not listed at all.

It has everything to do with the use of MCPs under the rules of the NEC. The NEC says they can only be used as part of a "listed combintation motor controller". The UL Guide information spells out the conditions of use for "listed combintation motor controllers".

 

[don_resqcapt19]

Would this include an MCP on the primary side of a VFD? You would be more inclined to see a TM UL 489 listed breaker there since it would be very doubtful for an MCP to protect a motor circuit on the secondary side of a VFD as a part of a combination motor starter.

If the combination of the MCP and the VFD is listed as a "combination motor controller", it would be code compliant.

 

[templdl]

If the combination of the MCP and the VFD is listed as a "combination motor controller", it would be code compliant.

I am in total agreement with you Don. But the OP didn't establish that which was the basis for my question which remains unanswered. When an MCPs purpose is to protect a motor circuit from a motor L-G are L-L failure by place a VFD in between the MCP and the motor the MCP would most likely not respond to a motor failure?
The VFD probably would provide over current protection for the MCP.
But it would be interesting if what the OP described did have a UL listed combination rating.

 

[petersonra]

I am in total agreement with you Don. But the OP didn't establish that which was the basis for my question which remains unanswered. When an MCPs purpose is to protect a motor circuit from a motor L-G are L-L failure by place a VFD in between the MCP and the motor the MCP would most likely not respond to a motor failure?
The VFD probably would provide over current protection for the MCP.
But it would be interesting if what the OP described did have a UL listed combination rating.

take a look at the charts provided by schneider for the soft starters. they list both mcp and tm breakers as having UL testing for high sccr for use with specific starters. would UL make a list like that you were not allowed to use?

 

[templdl]

take a look at the charts provided by schneider for the soft starters. they list both mcp and tm breakers as having UL testing for high sccr for use with specific starters. would UL make a list like that you were not allowed to use?
View attachment 8903

Thanks, I see your point for soft starters. What I question is what a mag. only MCP contributes when there is a vfd between the MCP and the motor. What type of protection does the MCP provide for the motor circuit? I can see where the vfd will act as an overload which would provide OL protection for the MCP and the MCP may provide short circuit protection of the vfd but what type of protection would the MCP provide for the motor? I'm just trying to understand what the purpose of the MCP on the line side of a vfd is.

 

[templdl]

take a look at the charts provided by schneider for the soft starters. they list both mcp and tm breakers as having UL testing for high sccr for use with specific starters. would UL make a list like that you were not allowed to use?
View attachment 8903

Thanks, I see your point for soft starters. What I question is what a mag. only MCP contributes when there is a vfd between the MCP and the motor. What type of protection does the MCP provide for the motor circuit? I can see where the vfd will act as an overload which would provide OL protection for the MCP and the MCP may provide short circuit protection of the vfd but what type of protection would the MCP provide for the motor? I'm just trying to understand what the purpose of the MCP on the line side of a vfd is.

 

[don_resqcapt19]

take a look at the charts provided by schneider for the soft starters. they list both mcp and tm breakers as having UL testing for high sccr for use with specific starters. would UL make a list like that you were not allowed to use?

I am not sure how that complies with the UL White Book information. In my opinion, it would only work if the combination of parts are marked "combination motor controller". If the specific wording does not appear on the equipment or on a list of equipment that can be combined, then I see it as a violation of the rule in the NEC that only permits the MCP to be used as a part of a listed combination motor controller. Maybe that information is found somewhere in the Schneider document, but without that information, it gets a red tag from me.

 

[petersonra]

I am not sure how that complies with the UL White Book information. In my opinion, it would only work if the combination of parts are marked "combination motor controller". If the specific wording does not appear on the equipment or on a list of equipment that can be combined, then I see it as a violation of the rule in the NEC that only permits the MCP to be used as a part of a listed combination motor controller. Maybe that information is found somewhere in the Schneider document, but without that information, it gets a red tag from me.

I think you are taking the word "marking" too literally. UL allows such markings to be part of the instructions or on the boxes the parts come in.

 

[petersonra]

Thanks, I see your point for soft starters. What I question is what a mag. only MCP contributes when there is a vfd between the MCP and the motor. What type of protection does the MCP provide for the motor circuit? I can see where the vfd will act as an overload which would provide OL protection for the MCP and the MCP may provide short circuit protection of the vfd but what type of protection would the MCP provide for the motor? I'm just trying to understand what the purpose of the MCP on the line side of a vfd is.

It provides only SC protection, just as it does in a normal contactor circuit.

 

[jim dungar]

If the specific wording does not appear on the equipment or on a list of equipment that can be combined,...

So you would not approve Motor Control Centers that use buckets which contain starters and MCP's?
These individual buckets are not UL Listed as 'combination motor controller' under the UL White book reference you used.

How about control panels listed to UL508, they are not marked as a 'combination motor controller"?

 

[templdl]

It provides only SC protection, just as it does in a normal contactor circuit.

But it isn't a normal contactor circuit. The OP was referring to an VFD, your reference if using a soft start which is in no way a vfd. How can you provide short circuit protection for a motor when the motor is on the load side of a vfd and the MCP on the line side of the vfd? How can an MCP even see a motor fault as it would as being a part of a common combination motor starter consisting of an MCP, contactor, and an OLR?

 

[petersonra]

But it isn't a normal contactor circuit. The OP was referring to an VFD, your reference if using a soft start which is in no way a vfd. How can you provide short circuit protection for a motor when the motor is on the load side of a vfd and the MCP on the line side of the vfd? How can an MCP even see a motor fault as it would as being a part of a common combination motor starter consisting of an MCP, contactor, and an OLR?

presumably UL has figured this out as many vfds and soft starters have UL listings that allow this combination. there are some things I do not know enough about that I have to accept what others who presumably know more say.

I have even seen a few high SCCR combinations like 65kA where the TM breaker is only rated at 35kAIC. I guess if they test it and it works, it flies with UL.

 

[templdl]

presumably UL has figured this out as many vfds and soft starters have UL listings that allow this combination. there are some things I do not know enough about that I have to accept what others who presumably know more say.

I have even seen a few high SCCR combinations like 65kA where the TM breaker is only rated at 35kAIC. I guess if they test it and it works, it flies with UL.

What you have finally confirmed is the you do have VFDs that do have MCPs of the primary that have a UL listing.
Also, MCPs do not have an interrupting rating as the interrupting rating is dependent upon a combination test as a combination starter which in your case is 65ksic which is a common combination rating. Also, you happen to have a TH
M breaker that is 35kaic. If required the TM breaker could be replaced with TM breaker with a rating of 65kaic.
It doesn't make any sense to me either that an MCP located on the line side of a vfd is able to protect the motor circuit on the load side.
If it is a UL listed then it's allowed.

 

[don_resqcapt19]

I think you are taking the word "marking" too literally. UL allows such markings to be part of the instructions or on the boxes the parts come in.

That is true, but a catalog cut page is not enough, and the markings or instructions must state exactly what components are required to be used to create a listed combination motor controller.

 

[don_resqcapt19]

So you would not approve Motor Control Centers that use buckets which contain starters and MCP's?
These individual buckets are not UL Listed as 'combination motor controller' under the UL White book reference you used.

How about control panels listed to UL508, they are not marked as a 'combination motor controller"?

Then what provision of the code permits the use of the instantaneous trip breaker in a MCC bucket? To me the code is clear that an instantaneous trip breaker can only be used as part of a listed combination motor controller.

430.52(C)(3) Instantaneous Trip Circuit Breaker. An instantaneous trip circuit breaker shall be used only if adjustable and if part of a listed combination motor controller having coordinated motor overload and short-circuit and ground-fault protection in each conductor, and the setting is adjusted to no more than the value specified in Table 430.52.