Sizing a Service- Weakest Link Method

[Paul W. Abernathy]

Hey Guys,

I found this file and updated it for you all. Enjoy !

http://www.youtube.com/watch?v=b499RKjLroA

[Bruce A. King]

Paul, What is your opinion on reporting subpanel amperage? I see many inspectors just list the rating of the enclosure in the report as opposed to listing the amperage of the feeder circuit. I think the correct way is to list the available amps on these that you can actually use without modifications. Listing the rating of the enclosure is fine too but the real number should be disclosed in the report.

[Paul W. Abernathy]

When sizing a Remote Distribution Panel , you still have the same basic components. Feeder size, Feeder Breaker Size, Enclosure Rating. Just remember that the enclosure rating is not something we can rely on much because a 100A rated feeder protected by a 100A OCPD supplying a remote distribution panel with a rating of 150A would still be only 100A.

[Jim Port]

I agree with you Bruce. A panel rated for 100 amps but fed with a 2 pole 40 would be a 40 amp subpanel to me.

[Paul W. Abernathy]

Hmmm.......ahhh.....is that not what I typed using my example?

[Robert Meier]

Nice video, I like the weakest link concept. One thing that I didn't hear mentioned in your example is that your 200 amp main CB is protecting a panelboard only rated for 150 amps which could become a problem if the load ever exceeds 150 amps.

[Paul W. Abernathy]

Remember now...we are only giving examples of the components of sizing using an extreme example as mentioned in the oopening statement. Once it is defered to the contractor amoung other issues it will be evaluated. The effort was simply to give an example of sizing for a home inspection report.

I agree in that example it should be reported that the enclosure is only 150A rated....and you are correct in that over 150A load could effect this....just remember when I do these short videos, I can't cover everything in order to keep viewers focused on the intent of the video itself.

[Paul W. Abernathy]

But......I must add.......That is a GREAT point inspectors should remember when reporting the issues......other than just trying to size it.