INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Jobs

sizing the cable size and the CB for the capacitor

sizing the cable size and the CB for the capacitor

(OP)
when we design cable size for the capacitor we multiply the normal current by 1.35 and the CB shall be size to 1.5*normal current?

does my statement above true?

regards

RE: sizing the cable size and the CB for the capacitor

Indeed ,NEC Art.460 Capacitors. 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.
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.
240.4 Protection of Conductors.
Conductors, other than flexible cords, flexible cables, and fixture wires, shall be protected against overcurrent in accordance with their ampacities specified in 310.15, unless otherwise permitted or required in 240.4(A) through (G).
In my opinion that means in order to protect the conductors CB rating has to be 135% also.
460.9 Rating or Setting of Motor Overload Device.
“Where a motor installation includes a capacitor connected on the load side of the motor overload device, the rating or setting of the motor overload device shall be based on the improved power factor of the motor circuit.
The effect of the capacitor shall be disregarded in determining the motor circuit conductor rating in accordance with 430.22.”
In my opinion, that means in order to protect the conductors CB rating has to be 125% motor rated current.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close