Q. A 400A service is made up of two 200A main breaker panelboards that are nippled together. Can the service conductors pass through one of the cabinets to supply the other panelboard?

A. Yes. Cabinets, cutout boxes, and meter socket enclosures can be used as a raceway for conductors that feed through if the conductors don’t fill the wiring space at any cross section to more than 40% [312.8].