Advanced Electrical Course Question

The video says that the capacity for a home is based on the lesser of the following items:

  1. The size of the service conductor
  2. The Rating of the Main Breaker
  3. The rating of the panel.
    In other words, if the conductor is rated for 200 amp, the breaker is rated for 200 amps but the panel is rated for 150 amps then the capacity for the home is considered 150 amps? Is this correct? Shouldn’t the panel be called out for being undersized?

From “Electrical Panel Inspection Training Video” course - Page 27 - InterNACHI Inspection Forum http://www.nachi.org/forum/f74/electrical-panel-inspection-training-video-course-76449/index27.html#ixzz3j4i9fFtH

Yes, the OCPD needs to be 150 amps in your example. The panel could be rated for 200amps with an OCPD of 150 amp which would make it a 150 amp service.

I understand how to determine the capacity. My question is this: Is it considered a defect if the panel rating is less than the conductor? Also, Is it a defect if the OCPD is rated higher than the Conductor? If so, do you consider this a material defect?

If the ocpd is correct the panel can be larger than the conductor capacity.

Yes, the OCPD needs to be 150 amps if the panel is 150 amps, since it’s a 200 amp CB then it’ a defect.

Since others have answered the core of your question, as a wire and cable guy I will answer the above portion.

As long as the lugs to which the conductors terminate are sized properly and terminated properly to accept a larger conductor then no harm will come to the conductor of course. As long as again it is permitted within the size range of the lug it is being applied.

I made a proposal to Section 110 of the NEC to demand a marking on all conductors that were increased in size for any reason so that future service people know exactly why it was increased in size…and the CMP shot it down (in fact the only one out of my 25 public inputs that did not get accepted)…their substantiation is that it should have been in Article 310…well you should have sent it to that CMP for review…but alas it was not.