Circuit Types 1. Singlephase circuits - a singlephase circuit may be two wire (120 volts, 208 or 240 volts, or 480 volts line to
line); three wire (120 volts line to neutral and 208/240 volts line to line or 208/240 line to neutral and 480 volts line to line). 
Note: Parantheses indicate other possible voltages that might be available. Three wire circuit voltages may be
120/240 volt line-groundline-line or 240/480 volt line-groundline-line. Meters are rated 240 or 480 volt respectively.
2. Polyphase circuits - a polyphase 3 phase circuit may be: 3-wire network, 3-wire, 4-wire delta, or 4-wire wye. 
(120/208V or 277/480V) or meter rated 120 or 240V using line-to-ground voltage. A 240 volt meter is used for 277/480V service. |
(One phase may or may not be grounded.) Meter rated 120, 240 or 480 volt. |

(120/240V or 240/480V) Meter rated 240 or 480 volt using line-to-line voltage. |
(120/208V or 277/480V) Meter rated 120 or 277 volt using line-to-ground voltage. If 240/416 service (uncommon), meter rated 240 volt, 240 and 277 volt wye meters are applicable
to either 240/416 or 277/480 volt wye service, 240 volt meters have 240V nameplates and are calibrated at 240V. 277 volt meters have 277V nameplates and are calibrated at 277V. |
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