One of the major Code defects in my current house that I want to rectify at some point is the fact that the (only) panelboard is mounted too high up on the wall (the current panelboard's service disconnect handle is around the 6'7" limit). Since the panelboard is a 60+ year old, all-fuse Wadsworth that is already short on circuit spaces for the house -- what is suspected to be the air conditioner circuit breaker is mounted in a cutout box, sans cover, above the panelboard -- replacement with a modern unit seems like the cleanest option.
However, this creates a problem -- the existing service-entrance conductors likely don't have enough length to reach the new panelboard location, and likewise for the branch circuit conductors entering the panelboard. So, I was thinking that the ideal solution to the problem would be to use an auxiliary gutter atop the panelboard to house splices between "pigtails" extending from the panelboard to their mating service-entrance and branch-circuit conductors, thus providing a neatly packaged solution without having to abuse the old panelboard cabinet as a junction box.
However, NEC 230.7 prohibits commingling service conductors with non-service conductors in the same "raceway or cable".
230.7 Other Conductors in Raceway or Cable.
Conductors other than service conductors shall not be installed in the same service raceway or service cable.
Exception No.1: Grounding electrode conductors and equipment bonding jumpers or conductors.
Exception No.2: Load management control conductors having overcurrent protection.
This raises two questions, though. First, the Code uses "service-entrance conductor" instead of "service conductor" to presumably refer to the conductor from the meter base to the service disconnect with "service conductor" referring to the utility's conductors up to the meter, which would mean that under my interpretation, the commingling issue is moot. However, there's also the interpretation that a "service-entrance conductor" is a kind of "service conductor", which'd mean that 230.7 would apply to "service-entrance conductors" as well.
Furthermore, is an auxiliary gutter a raceway? One would think not, since they do not follow raceway fill rules, are authorized to contain splices and taps "by default" in 366.56 (which is not cited as an exception by 300.13 which normally prohibits splices in raceways) as well as 300.15(A), and follow different ampacity derating rules as per 366.23. However, I am sure that someone who just looked at the Article 100 definition of "raceway" by itself would see no reason it wouldn't apply to auxiliary gutters:
Raceway. An enclosed channel of metallic or nonmetallic materials designed expressly for holding wires, cables, or bus- bars, with additional functions as permitted in this Code.
Finally, in 366.2, the Code definition of what an auxiliary gutter is designed to be used with refers to "meter centers, distribution centers, switchgear, switchboards, and similar points of wiring systems".
Metallic Auxiliary Gutter. A sheet metal enclosure used to supplement wiring spaces at meter centers, distribution centers, switchgear, switchboards, and similar points of wiring systems. The enclosure has hinged or removable covers for housing and protecting electrical wires, cable, and busbars. The enclosure is designed for conductors to be laid or set in place after the enclosures have been installed as a complete system.
Does that phrase include panelboards (including residential-type panelboards/load centers)? Or is using an auxiliary gutter with a panelboard/load center a Code violation as the gutter suddenly ceases to be a gutter by way of what it's mated to, leaving you with wires and splices in something that's not any kind of enclosure the Code recognizes?