I am not sure I understand why the calculated motor branch circuit (@4:00) 35A was sized per 75 degrees columns instead of 60 degrees column in T310.16(B)(16). Since it is less tha 100 amp
Samuel, we appreciate your comment! The degree column used is based on the rating of the terminals on the motor, and in this case, the graphic did not list the terminals as 75 degrees. Our current graphics have been updated to include the terminal ratings. Here is a video link covering the topic in more detail. ua-cam.com/video/k7d03Tic6LE/v-deo.htmlm57s
Thank you! What about an AC Servo Motors. Do they obey the same rules as regular AC motors? If the manufacturer of the VFD or servo motor Drives recommends nominal of MCB. do I need to consider these recommendations?
Just use the table and use 250% for protection. If the 250% of the FLC does not match a standard breaker, then you are permitted to go up to the next size.
Marielle, great question! We didn’t discuss choosing 115% vs 125% for the overload protection since it wasn’t the focus of the video. According to 430.32, you use 115% for the overload protection if the service factor is less than 1.15 or has a temperature rating less than 40C. We cover this in great detail in our Exam Prep library. www.mikeholt.com/journeymanexamprep.php
Hola (hi). Que sucede cuando el motor es alimentado por un variador de frecuencia / varidor de velocidad? (What happen when a motor is fed by a Variable frequency drive?)
7:00... never a good idea to use fuses for motor overload protection... especially if the motor is 3-phase... a slow load increase such as a pump with increased fluid weight could cause the motor to burn up before the fuses would open.... and single phasing a 3-phase motor is almost a guarantee to burn up the windings
![Branch Circuit, Multiwire, NEC 2020 - [210.4], (19min:38sec)](http://i.ytimg.com/vi/Qynp92rIlYg/mqdefault.jpg)
the most important is when use FLA and FLC ,i think mike explain clear,thanks mike,casanova electric contractor
I am not sure I understand why the calculated motor branch circuit (@4:00) 35A was sized per 75 degrees columns instead of 60 degrees column in T310.16(B)(16). Since it is less tha 100 amp
Samuel, we appreciate your comment! The degree column used is based on the rating of the terminals on the motor, and in this case, the graphic did not list the terminals as 75 degrees. Our current graphics have been updated to include the terminal ratings. Here is a video link covering the topic in more detail. ua-cam.com/video/k7d03Tic6LE/v-deo.htmlm57s
For short circuit and ground fault protection, where do we get 250% or 2.5 from?
NEC 430.53
In your single protection device boat lift motor example how did you size the 6.125A conductor to 14 AWG
I was thinking add a limit switch all along to Mikes boat lift to stop burning up motors. But a 5 amp fuse works just as well. Haha
Thank you! What about an AC Servo Motors. Do they obey the same rules as regular AC motors? If the manufacturer of the VFD or servo motor Drives recommends nominal of MCB. do I need to consider these recommendations?
Please post your question on MikeHolt.com/Fourm.
@@MikeHoltNEC I did it 3 days ago
I still do not understand where the 250% is found. How do you use 430.52 and table 430.52 for protective device sizing? I’m so confused.
Just use the table and use 250% for protection. If the 250% of the FLC does not match a standard breaker, then you are permitted to go up to the next size.
Great video.... 5:42- looks like a din rail mountable fuse block with an optional aux contact to me...
You also need limit switches for your lift motor.
why is the overload protection in 1:58 is 1.15 instead of 1.25?
Marielle, great question! We didn’t discuss choosing 115% vs 125% for the overload protection since it wasn’t the focus of the video. According to 430.32, you use 115% for the overload protection if the service factor is less than 1.15 or has a temperature rating less than 40C. We cover this in great detail in our Exam Prep library. www.mikeholt.com/journeymanexamprep.php
I caught this too.
Hola (hi). Que sucede cuando el motor es alimentado por un variador de frecuencia / varidor de velocidad? (What happen when a motor is fed by a Variable frequency drive?)
The the circuit conductor and protection is in accordance with manufacturere instructions, not 430.22.
MikeHoltNEC conductors manufacture? Or variable frequency drive manufacture? Thank you very much!!
@@carlosvillegas2167 VFD manufacturer.
great videos !
If the motor is 50 Hz (380 V) !! What should i do ? Can you help me ..please
Please post your question on MikeHolt.com/Forum
Why is my circuit breaker 70amps? If motor is only 29.9 amps at full capacity
Because of motor start up current.
7:00... never a good idea to use fuses for motor overload protection... especially if the motor is 3-phase... a slow load increase such as a pump with increased fluid weight could cause the motor to burn up before the fuses would open.... and single phasing a 3-phase motor is almost a guarantee to burn up the windings
Zeke Slaaen Or you can use a motor starter with phase loss protection.
Use positive overload protection in your starter?