National Electrical Code questions

I subscribe to the newsletter of Mike Holt which keeps me more or less up to date on changes and improvements and advice from the National Electrical Code.

Q. What is the maximum number of circuit breakers permitted to be installed in a panel?
A. The maximum number of circuit breakers permitted in a panelboard is limited by the instructions posted inside the panelboard [110.3(B)]. However, the NEC specifies that not more than 42 overcurrent devices can be installed in any one cabinet [408.15].

Q. Is there a code limitation as to the total ampere rating of all circuit breakers in a panel? Example: Could the total ampere rating of all circuit breakers in a 100A panel exceed 100A?
A. This is not a Code issue. The sum of the ampere rating of the circuit breakers in a panelboard is irrelevant. As a matter of fact, it is very common for the total ampere rating of the branch breakers in a panelboard to far exceed the rating of the panelboard.

Q. Does the NEC state the number of NM cables permitted under a single staple?
A. No. NM cable must be secured and supported in accordance with 334.30 which states that nonmetallic-sheathed cable must be secured by staples, cable ties, straps, hangers, or similar fittings designed and installed so as not to damage the cable. However, this section does not specify the maximum number of cables permitted under a single staple. As always, the installation must be approved by the authority having jurisdiction [90.4], so basically it's up to the inspector.