/ Field knowledge · NEC 100 · Sparky Edition
“208 volts” is not a complete voltage description.
NEC Article 100: two submittals can both say “208 volts” and still leave a coordination gap. Nominal voltage is a system class, not a promised field reading.
Educational 2026 NEC Article 100 terminology. Confirm the adopted edition. This is not a voltage-drop or conductor-sizing calculation. Field observations do not establish electrical safety; only qualified personnel using required safe-work procedures should access electrical equipment.
- Nominal voltage identifies a system class. Line-to-line is between phase conductors. Line-to-neutral is between a phase and neutral.
- Voltage to ground uses the applicable system grounding relationship — do not assume it means line-to-neutral on every system. For an ungrounded circuit, the NEC definition uses the greatest voltage between the conductor concerned and another circuit conductor. A casual meter-to-earth observation is not that identification.
- Balanced wye: line-to-line is approximately 1.732 × line-to-neutral. 208Y/120 V is nominal 208 V phase-to-phase and 120 V phase-to-neutral. 480Y/277 V is 480 V and 277 V. The Y indicates wye. That ratio is not a shortcut for 120/240 V single-phase, a high-leg delta, or every system labeled 208 or 480 V.
A 480 V three-phase motor commonly uses line-to-line without a neutral; a packaged assembly may separately need a neutral or a control transformer. A 277 V lighting load has different connection requirements. A motor marked for one utilization voltage should not be assumed suitable for another nominal supply without manufacturer support.
Schedule 208 V 3Ø, submittal needs a neutral
Resolve that mismatch in writing before ordering. Record conflicting labels rather than choosing the value that makes a replacement fit. A single measured value does not establish voltage stability, phase balance, grounding arrangement, or capacity.
Source: Sparky voltage · listed: listed/labeled · SCCR: SCCR.
What to send
The equipment schedule, the submittal nameplate, and the one-line voltage basis (safe photos only).
If the schedule says 208 V and the nameplate does not
Send both. Masterbuild will say whether Article 100 even has a complete voltage description — or a 480 V motor is about to land on 208 V.
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