Are 120/240 V and 277/480 V systems both considered low voltage? Why or why not?

• A. No, only 120/240 V is LV
• B. Yes; LV generally up to 600 V; 277/480 are common in commercial/industrial lighting and distribution
• C. Yes; all voltages under 1000 V are LV
• D. No; low voltage means less than 50 V

Answer: (B)

Low voltage is defined by the maximum operating voltage of the system, with the standard cutoff being about 600 volts. That means both 120/240 V and 277/480 V fall into the low‑voltage category because their voltages do not exceed 600 V (the 277/480 system carries 480 V line-to-line and 277 V line-to-neutral). The 277/480 V arrangement is common in commercial and industrial settings for lighting and distribution, and equipment for these voltages is designed to meet LV safety standards. Some contexts call voltages like 480 V “medium voltage,” but within the typical LV definition, 480 V is still considered low voltage.