# When is an OCPD not an OCPD?



## Electron_Sam78 (Feb 26, 2010)

According to the NEC is there anywhere that defines the end of the circuits in question in relation to the final OCPD when talking about the definition of a branch circuit? For instance an RV pedestal that contains circuit breakers and receptacles or a lift station control panel that contains circuit breakers. What if a plug in lamp has an inline fuse? What if a hard wired motor had an inline fuse after the final ocpd? Would the inline fuse become the final OCPD even if it was in the permanent wiring of the motor?


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## MDShunk (Jan 7, 2007)

In the case of cord and plug connected equipment, the OCPD supplies the receptacle, without regard to what may or may not be plugged into it.


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## Electron_Sam78 (Feb 26, 2010)

I agree :thumbup:. I'd also say that the point where the permanent wiring of the utilization equipment connects to the building or structure wiring is the outlet and any OCPD within the utilization equipment does not count as the final OCPD. Any disagreement or NEC conflicts with that general statement? Any gray areas to address?


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## RIVETER (Sep 26, 2009)

Electron_Sam78 said:


> I agree :thumbup:. I'd also say that the point where the permanent wiring of the utilization equipment connects to the building or structure wiring is the outlet and any OCPD within the utilization equipment does not count as the final OCPD. Any disagreement or NEC conflicts with that general statement? Any gray areas to address?


OCPD as far as we are concerned has to do with the utilization outlet...not the equipment. Circuit conductors are the protected items.


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## TOOL_5150 (Aug 27, 2007)

Q: When is an OCPD not an OCPD?
A: When it is made by FPE.

~Matt


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## micromind (Aug 11, 2007)

The OCPD of a motor is its O/L, not the breaker or fuse. 

This is why, for example, it's completely code-compliant to have a #14 on a 40 amp breaker. The breaker (or fuse) is for short-circuit and ground-fault protection only. Overcurrent is accomplished by the overload protection of the motor.


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## RIVETER (Sep 26, 2009)

micromind said:


> The OCPD of a motor is its O/L, not the breaker or fuse.
> 
> This is why, for example, it's completely code-compliant to have a #14 on a 40 amp breaker. The breaker (or fuse) is for short-circuit and ground-fault protection only. Overcurrent is accomplished by the overload protection of the motor.


Maybe I've had too much salsa but I have never known that a person should place a # 14 conductor on a 40 amp circuit.:no:


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## slickvic277 (Feb 5, 2009)

RIVETER said:


> Maybe I've had too much salsa but I have never known that a person should place a # 14 conductor on a 40 amp circuit.:no:



definitely to much salsa.


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## RIVETER (Sep 26, 2009)

slickvic277 said:


> definitely to much salsa.


Are you saying that that is a true statement?


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## slickvic277 (Feb 5, 2009)

RIVETER said:


> Are you saying that that is a true statement?


Yes. I am.


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## RIVETER (Sep 26, 2009)

slickvic277 said:


> Yes. I am.


We need to talk.


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## Bkessler (Feb 14, 2007)

micromind said:


> The OCPD of a motor is its O/L, not the breaker or fuse.
> 
> This is why, for example, it's completely code-compliant to have a #14 on a 40 amp breaker. The breaker (or fuse) is for short-circuit and ground-fault protection only. Overcurrent is accomplished by the overload protection of the motor.


definitely a fact


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## slickvic277 (Feb 5, 2009)

RIVETER said:


> We need to talk.


About what?

His example of motor protection was spot on.
In motor loads the breaker/fuse is used for short circuit and ground fault protection only. The over current protection comes in the form of over loads. Sometimes referred to as "heaters".

The reason why the breaker/fuse can be many times larger then the circuit conductors is due to the LRC of the motor.


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## RIVETER (Sep 26, 2009)

slickvic277 said:


> About what?


Okay, I will start by saying that there is a possibility of me being wrong, so don't get "up in arms". My thinking is that the OCPD device for a circuit is supposed to be for the protection of the insulation of the properly sized conductor. Sure, a device that draws too much current, such as a motor in a seized up condition may trip out on it's "on board" OCPD could be serviced with an undersized circuit conductor, but is that what you think you should plan on? My thinking is that the OCPD is there to protect the circuit conductors. What if a short to ground occurs at the pecker-head just short of the windings?


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## Electron_Sam78 (Feb 26, 2010)

Ok so a motor with an inline fuse wasn't the best example but it really wasn't the point of the thread.


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## RIVETER (Sep 26, 2009)

Electron_Sam78 said:


> Ok so a motor with an inline fuse wasn't the best example but it really wasn't the point of the thread.


Don't fret...we'll argue (discuss) it anyway.


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## Magnettica (Jan 23, 2007)

TOOL_5150 said:


> Q: When is an OCPD not an OCPD?
> A: When it is made by FPE.
> 
> ~Matt


:laughing:


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## user438 (Jun 6, 2007)

RIVETER said:


> Okay, I will start by saying that there is a possibility of me being wrong, so don't get "up in arms". My thinking is that the OCPD device for a circuit is supposed to be for the protection of the insulation of the properly sized conductor. Sure, a device that draws too much current, such as a motor in a seized up condition may trip out on it's "on board" OCPD could be serviced with an undersized circuit conductor, but is that what you think you should plan on? My thinking is that the OCPD is there to protect the circuit conductors. What if a short to ground occurs at the pecker-head just short of the windings?


 
The breaker will trip, it is still providing short circuit /ground fault protection regardless of wire size. The overloads will trip out if the motor is overloading, wires are still sized based on the motors rated current draw. The breaker is simply oversized to allow for inrush/locked rotor current. Breakers have a smaller trip curve than an overload/heater


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## slickvic277 (Feb 5, 2009)

> RIVETER;Okay, I will start by saying that there is a possibility of me being wrong, so don't get "up in arms"


Nobody's "up in arms".



> . My thinking is that the OCPD device for a circuit is supposed to be for the protection of the insulation of the properly sized conductor


OK. I would say the OCP is dictated by the size AND insulation type of the conductor.



> . Sure, a device that draws too much current, such as a motor in a seized up condition may trip out on it's "on board" OCPD could be serviced with an undersized circuit conductor, but is that what you think you should plan on?


It's not what I think. It's what the NEC allows. Frankly, I'm not smart enough to contradict the NEC. 



> My thinking is that the OCPD is there to protect the circuit conductors.


It is. But in the case of a motor circuit the fuse/breaker is only there to protect against ground faults and short circuits. The reason why the breaker or fuse is up-sized so much is to handle the in rush current.
The over load device will be sized correctly accordingly to the size of the conductors (which are sized according to the motor)



> What if a short to ground occurs at the pecker-head just short of the windings?


The breaker or the fuse will open.


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## slickvic277 (Feb 5, 2009)

Rich R said:


> The breaker will trip, it is still providing short circuit /ground fault protection regardless of wire size. The overloads will trip out if the motor is overloading, wires are still sized based on the motors rated current draw. The breaker is simply oversized to allow for inrush/locked rotor current. Breakers have a smaller trip curve than an overload/heater


:thumbsup:

You explained it better then me.


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## user438 (Jun 6, 2007)

slickvic277 said:


> :thumbsup:
> 
> You explained it better then me.


That's cause I don't eat scrapple :thumbsup:


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## MDShunk (Jan 7, 2007)

Rich R said:


> That's cause I don't eat scrapple :thumbsup:


I wonder if you can even get scrapple in FL?

My wife tells me she doesn't eat anything with crap in the name.


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## frenchelectrican (Mar 15, 2007)

micromind said:


> The OCPD of a motor is its O/L, not the breaker or fuse.
> 
> This is why, for example, it's completely code-compliant to have a #14 on a 40 amp breaker. The breaker (or fuse) is for short-circuit and ground-fault protection only. Overcurrent is accomplished by the overload protection of the motor.


That set up is legit 100%.

All you have to do is look up Art 430 and Art 440 both will cover this part very clear.

But don't start with moi with nonhard wired motours ! (Merde!)

Merci.
Marc


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## slickvic277 (Feb 5, 2009)

Rich R said:


> That's cause I don't eat scrapple :thumbsup:


Your missing out.




MDShunk said:


> I wonder if you can even get scrapple in FL?
> 
> My wife tells me she doesn't eat anything with crap in the name.


Don't tell me that a Pennsylvanian such as yourself doesn't enjoy scrapple.
How disappointing.


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## HAND (Jul 15, 2010)

Electron_Sam78 said:


> According to the NEC is there anywhere that defines the end of the circuits in question in relation to the final OCPD when talking about the definition of a branch circuit? For instance an RV pedestal that contains circuit breakers and receptacles or a lift station control panel that contains circuit breakers. What if a plug in lamp has an inline fuse? What if a hard wired motor had an inline fuse after the final ocpd? Would the inline fuse become the final OCPD even if it was in the permanent wiring of the motor?


You are allowed to use those supplementary ocpd but the cannot be the ocpd required at the source.


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## Electron_Sam78 (Feb 26, 2010)

don't care about the source. I'm interested in the final OCPD


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