Need Assistance with Electrical Panel

That table is for dwellings so for a dwelling service it is correct. I eyeballed the panel in the photo and it does not appear to be a dwelling panel so the proper NEC table would be 310.16. If it is a dwelling then I stand corrected the #2/0 is permitted for 200 amps.

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Ok roger that :+1:

I didn’t realize that this may have been a commercial inspection and that the requirements are different for commercial vs dwelling.

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Sorry I should have provided that information.
Yes this is a residential house.

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Thanks for clarifying, that is a very strange setup for a single family home.

Yes. That why I asked for help.
Large house almost 3800 Square Feet.
Property also had a well.

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what is the reason for the difference? 200 amps is 200 amps in commercial and residential.

The size of the service is decided by a load calculation. Dwelling load calculations have quite a large diversity factor built into the calculation so the NEC only requires that the conductors serving the service disconnecting means be sized at a minimum of 83% of the size of the service disconnect OCPD. For other than dwellings your conductors would be sized at a minimum of 100% of the OCPD size.

There is a separate table in the NEC which would allow #2/0 to be protected at 200 amps for dwellings even though #2/0 Cu is only rated for 175 amps. For a commercial service #3/0 Cu would be the minimum size for 200 amps.

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Current ratings for conductors are relative, not absolute, numbers. They are based on several factors. Most notably, major factors are:

  1. Calculated demand
  2. Time (I/T)
  3. Environment (ambient temperature, heat disapation capacity)
  4. Reactance (power factor).
  5. Statistical data.

Residial loads are simple and predictable. Non-residential loads are usually more complex. Large non-residential systems often do not exactly follow the NEC because they are designed by electrical engineers. The NEC is mainly used for residential and non-residential systems that are not designed by electrical engineers.

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thanx to both of you for those helpful and in-depth answers. lots of good knowledge in this place.

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