NEC 480.9(A) / NFPA 1 52.3.3

NEC 440.14

NEC 440.14 requires the disconnecting means to be within sight from and readily accessible from the air-conditioning or refrigerating equipment. 'Within sight' (or 'In Sight From') per NEC Article 100 means the equipment is visible AND not more than 50 feet distant. The scenario satisfies both: the disconnect is visible from the unit and only 30 feet away (under the 50-foot limit), and it is readily accessible on the exterior wall. There is NO NEC requirement that the disconnect be on the 'same level' as the equipment or that the servicer never leave the rooftop — a wall-mounted disconnect that is visible, within 50 feet, and readily accessible is fully compliant. The installation meets 440.14.

NEC 445.18 / NFPA 110 7.2

An emergency stop accessible from outside the generator room is required so operators can shut down the generator without entering a potentially hazardous space (fire, fuel leak, or excessive noise). NEC 445.18 requires a readily accessible disconnecting means.

NEC 460.8 / VFD Manufacturer Guidelines

Power factor correction capacitors must never be installed on the output side of a VFD. The capacitors resonate with the VFD's PWM switching frequency, causing destructive overcurrents that will fail the capacitors and potentially damage the drive. Capacitors go on the input side only.

NEC 500.8 / NFPA 497 Chapter 5

Disconnect switches within the classified hazardous area boundary of a flammable liquid dispensing point must be rated for the area classification. NEC Table 514.3 and NFPA 497 define the extent of classified areas around dispensing points. A non-rated switch can produce arcs that ignite flammable vapors.

NEC 501.10(B) / NEC 501.15

All conduit fittings in Class I, Division 2 locations must be listed for the specific hazardous classification. Standard fittings can allow ignitable concentrations of gas to migrate through the conduit system. NEC 501.10(B) requires conduit seals and listed fittings to prevent gas migration and potential ignition.

NEC 501.125(B)

This is code-compliant. NEC 501.125(B) explicitly permits the installation of open or nonexplosionproof enclosed motors — such as squirrel-cage induction motors WITHOUT brushes, switching mechanisms, or similar arc-producing devices — in Class I, Division 2 locations. Explosionproof or totally-enclosed construction is NOT required for these motors in Division 2. An ODP squirrel-cage induction motor with no normally-arcing components is precisely the type the code allows, and the engineer's reasoning is sound: Division 2 means a flammable concentration is present only under abnormal conditions, and a brushless induction motor has no arc source during normal operation. The only conditions are that the motor has no arc-producing devices (satisfied here) and that its maximum external surface temperature not exceed the temperature limit (T-code / 80% of the gas group autoignition temperature). The scenario states no over-temperature condition, so the installation passes. (Had the scenario specified a surface temperature exceeding the gas AIT limit, it would fail — but as written it does not.)