When determining the size of a 120/240-volt 1Ø, 3-wire service, how is the lighting load in amps calculated?

The calculation of the lighting load in amps for a 120/240-volt single-phase, three-wire service involves understanding the relationship between power (in volt-amps or watts), voltage, and current (in amps).

To find the current in amps, you divide the lighting load measured in volt-amps by the voltage level. In this case, since the service is rated at 240 volts, this relation can be expressed with the formula:

[ \text{Amps} = \frac{\text{Volt-Amps}}{\text{Volts}} ]

By applying this formula, if you take the total lighting load in volt-amps and divide it by the service voltage of 240 volts, you obtain the current drawn by the lighting loads in amps. This is crucial for determining whether the existing service can handle the load and for conducting safe and efficient installations.

Thus, the correct approach aligns with the principle of Ohm's law and power relationships, ensuring accurate calculations necessary for proper electrical service management.