motor condutor tap

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don_resqcapt19

don_resqcapt19

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I have a couple of questions about tapping the motor circuit conductors at the motor for the installation of a power factor correction system. The equipment to be installed has a 50 amp OCPD and the motor is a 200 hp, 480 volt motor.
1) Are motor circuit conductors between the controller and the starter branch circuit conductors? If so, then 210.19 would apply and make the installation a code violation. I am assuming that 210.19 does not apply because the installation of power factor correction equipment at the motor is not uncommon.
2) Assuming that I can use the feeder tap rule in 240.21(B)(2) can I use the rating of the motor overload protector to size the tap conductors.
Don
 
don_resqcapt19 said:
I have a couple of questions about tapping the motor circuit conductors at the motor for the installation of a power factor correction system. The equipment to be installed has a 50 amp OCPD and the motor is a 200 hp, 480 volt motor.
1) Are motor circuit conductors between the controller and the starter branch circuit conductors? If so, then 210.19 would apply and make the installation a code violation. I am assuming that 210.19 does not apply because the installation of power factor correction equipment at the motor is not uncommon.
2) Assuming that I can use the feeder tap rule in 240.21(B)(2) can I use the rating of the motor overload protector to size the tap conductors.
Don
Click to expand...

Don,,
Ya gave me a good challange but let me answer this question on the question #2

yes you can use the feeder tap rule but you have to keep in your mind when you installed the power factor correction device you may have to change the O/L heaters [ some case it will drop the current to some degress but how much i dont know that part ]

Ok, let get back to the question #1 i can see what you are refering to this on 210.19 but if installed on the motor end at the peckerhead the 210.19 go out of the window if the O/L is resized

but you have to forgive my blunt but i know there were a digram somewhere it did illustred how this been done to meet the NEC codes.

but just off the point for a sec do this powerfacter correction device do have the contractor on it or hardwired to the wires?

Thanks for your time

Merci , Marc
 
don_resqcapt19 said:
2) Assuming that I can use the feeder tap rule in 240.21(B)(2) can I use the rating of the motor overload protector to size the tap conductors.
Don
Click to expand...

Don, I think article 460.8 would apply to your conductors.The P.F.C. devices are basically capacitor banks.

460.8 Conductors
(A) Ampacity The ampacity of capacitor circuit conductors shall not be less than 135 percent of the rated current of the capacitor. The ampacity of conductors that connect a capacitor to the terminals of a motor or to motor circuit conductors shall not be less than one-third the ampacity of the motor circuit conductors and in no case less than 135 percent of the rated current of the capacitor.

Rick
 
Rick,
While 460 tells me how to size the conductors, the conductors still have to have overcurrent protection. The motor circuit conductors are branch circuit conductors and there is no provision that permits them to be tapped.
I am planning to treat the motor circuit conductors as feeders, but does the 1/3 ampacity have to be based on the motor circuit overcurrent protective device or can it be based on the motor overload protective device rating?
Don
 
Marc,
Ok, let get back to the question #1 i can see what you are refering to this on 210.19 but if installed on the motor end at the peckerhead the 210.19 go out of the window if the O/L is resized
Click to expand...
The O/L is an overload protective device and not an overcurrent protective device. The feeder tap rule requires a overcurrent protective device.
I know this is a common installation, but I don't think that the code rules actually permit it.
Don
 
Don ,

I relaized what you are expaining to me on this one,

Yes i know it was very common methold to do this and yes i will admit i overlook a little item you clear that part up.


I am planning to treat the motor circuit conductors as feeders, but does the 1/3 ampacity have to be based on the motor circuit overcurrent protective device or can it be based on the motor overload protective device rating
Click to expand...

I will just go with motor overcurrent protection device beacause in case if the power factor correction device fail and go off line and the motor current will go back to the normal current level [ preexsting ]

Merci, Marc
 
don_resqcapt19 said:
does the 1/3 ampacity have to be based on the motor circuit overcurrent protective device or can it be based on the motor overload protective device rating?
Don
Click to expand...
Don ,If you are tapping between the controller and O.L.'s then 1/3 would be of the OCP. If tapping on the motor end of the O.L.'s, then no OCP required for the tap, but OCP would be required for the P.F.C. device because it would be in an enclosure similar to an industrial control panel.

(B) Overcurrent Protection An overcurrent device shall be provided in each ungrounded conductor for each capacitor bank. The rating or setting of the overcurrent device shall be as low as practicable.

Exception: A separate overcurrent device shall not be required for a capacitor connected on the load side of a motor overload protective device.

Don, i am only picking articles out of the book to explain my thoughts.The few i put in were tapped off the main switch board, and the pfc had individual ocp.
Rick
 
Rick,
If you are tapping between the controller and O.L.'s then 1/3 would be of the OCP. If tapping on the motor end of the O.L.'s, then no OCP required for the tap,...
Click to expand...
What code section says that these conductors do not need overcurrent protection?
Don
 
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