HVAC Equipment

Three sub-topics of the Equipment & Devices area in one lesson: the A/C rules of Article 440 (a favorite source of calculation items), the panelboard rules of Article 408, and the working-space numbers of 110.26 that the "Workspace Clearance" sub-topic tests directly. Written from the 2023 text.

1. Article 440 — air-conditioning and refrigerating equipment

The nameplate does the engineering

• 440.4(A): a hermetic motor-compressor nameplate shows the rated-load current (RLA); locked-rotor current (LRA) is marked on single-phase compressors with RLA over 9 A at 115 V or over 4.5 A at 230 V, and on all polyphase compressors.
• 440.4(B): multimotor/combination-load equipment is marked with the minimum supply circuit conductor ampacity (MCA) and the maximum rating of the branch-circuit short-circuit and ground-fault protective device (MOCP), plus the controller SCCR.
• 440.4(C) branch-circuit selection current (BCSC): where marked (compressors whose protection permits continuous current above the 440.52 percentages), the BCSC is used instead of the RLA for every sizing rule.
• 440.6(A): the RLA (or BCSC where marked, whichever is greater) sizes the disconnect, branch-circuit conductors, controller, short-circuit/ground-fault protection and overload protection. (B): for shaded-pole or PSC fan/blower motors in multimotor equipment, use the FLC marked on the equipment nameplate, not the horsepower.
• 440.35: where MCA is marked, the branch-circuit conductors shall have an ampacity not less than the MCA — and the marked maximum OCPD is the ceiling (440.4(B) marks it from Part III; 440.22(B) Exception 1 and 440.22(C) say never exceed the manufacturer's marked values). On the exam, when a nameplate gives MCA/MOCP, those two numbers are the answer.
• 440.8: an A/C or refrigerating system is one machine for 430.87/430.112 even with remote motors; no A/C or refrigerating equipment in the 3 ft / 8 ft bathtub or shower zone.
• 440.9: equipment installed outdoors on a roof → a wire-type EGC in the outdoor portions of metal raceways that use compr